NIST NCSTAR 3
 

Final Report, National Institute of Standards 

and Technology (NIST) 

Technical Investigation of the May 22, 2011,

Tornado in Joplin, Missouri 

Erica D. Kuligowski 

Franklin T. Lombardo 

Long T. Phan 

Marc L. Levitan 

Engineering Laboratory 

National Institute of Standards and Technology 

David P. Jorgensen 

Warning R&D Division 

National Severe Storms Laboratory 

National Oceanic and Atmospheric Administration 

http://dx.doi.org/10.6028/NIST.NCSTAR.3 

March 2014 

U.S. Department of Commerce 

Penny Pritzker, Secretary 

National Institute of Standards and Technology 

Patrick D. Gallagher, Under Secretary of Commerce 

for Standards and Technology and Director 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Disclaimer No. 1 

Certain commercial entities, equipment, or materials may be identified in this document in order to describe an 

experimental procedure or concept adequately. Such identification is not intended to imply recommendation or 

endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, 

materials, or equipment are necessarily the best available for the purpose. 

Disclaimer No. 2 

NIST takes no position as to whether the design or construction of any building discussed in this report was 

compliant with any code. 

Disclaimer No. 3 

The policy of NIST is to use the International System of Units in all publications. In this document, however, units 

are presented in the system prevalent in the relevant discipline, although in some cases more than one system of 

units may be presented. 

Use in Legal Proceedings 

No part of any report resulting from a NIST investigation into a structural failure or from an investigation under the 

National Construction Safety Team Act may be used in any suit or action for damages arising out of any matter 

mentioned in such report (15 U.S.C. 281a, as amended). 

Copyright 

This NIST publication is a work of the United States Government not subject to copyright protection within the 

United States under Title 17 United States Code § 105. This publication may include copyrighted content (such as 

photographs) used with permission of the credited copyright holder. Reproduction, redistribution or reuse of such 

copyrighted content apart from this publication may require permission, which should be sought from the credited 

copyright holder. Where no copyright holder or source is credited for a figure or table in this publication, the source 

is NIST, which would appreciate attribution. 

National Institute of Standards and Technology National Construction Safety Team Act Report 3 

Natl. Inst. Stand. Technol. Natl. Constr. Sfty. Tm. Act Rpt. 3, 490 pages (March 2014) 

CODEN: NSPUE2 

Cover images (clockwise from top left): National Construction Safety Team member interviews Joplin tornado survivor (source 

NIST); ground (source FEMA Mitigation Assessment Team) and aerial (source NO!!) views of St; John’s Regional Medical 

Center; tornado wind field model (source NIST). 

Title page image: St; John’s Regional Medical Center (source NIST). 
 

 

 

 

NATIONAL CONSTRUCTION SAFETY TEAM
	

FOR THE NIST TECHNICAL INVESTIGATION
	

OF THE MAY 22, 2011,
	

TORNADO IN JOPLIN MISSOURI
	

Marc L. Levitan, Ph.D. (NIST), Lead Investigator
 

David P. Jorgensen, Ph.D. (NOAA)
 

Erica D. Kuligowski, Ph.D. (NIST)
 

Franklin T. Lombardo, Ph.D. (NIST)
 

Long T. Phan, Ph.D., P.E. (NIST)
 

NIST NCSTAR 3, Joplin Tornado Investigation iii 
 

National Construction Safety Team 

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. 

iv NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

CONTRIBUTORS TO THE INVESTIGATION 

National Construction Safety Team 

Marc L. Levitan Lead Investigator 

Franklin T. Lombardo Task Leader, Tornado Hazard Characteristics 

David P. Jorgensen Task Co–Leader, Tornado Hazard Characteristics 

Long T. Phan Task Leader, Performance of Buildings, Designated Safe Areas, and 

Lifelines as Related to Continuity of Building Operations 

Erica D. Kuligowski Task Leader, Emergency Communications, Public Response, and 

Fatalities and Injuries 

NIST Technical Staff 

Eric Letvin, Project Manager Rik Johnson Carolyn Sandler 

Jason Averill H. S. Lew Emil Simiu 

Steve Cauffman Therese McAllister Blaza Toman 

Andrew Flynn Nancy McNabb 

John Gross Fahim Sadek 

NIST Institutional Support 

Dorianna Andrade Michelle Harman Gail Porter 

Kellie Beall Jennifer Horning Carolyn Rowland 

Ami Carbaugh Jennifer Huergo Linda Beth Schilling 

Sonum Chaudhari Melissa Leiberman S. Shyam Sunder 

Kirk Dohne Darren Lowe Rose Van Camp 

Tina Faecke Mark Madsen Darla Yonder 

Catherine Fletcher Nicos Martys Bessmarie Young 

William Grosshandler Andrew Mundy Henry Wixon 

Howard Harary Michael E. Newman 

NIST Contractors 

Applied Research Associates BRI Consulting Group Jennifer Spinney 

Frank Lavelle Brian Garrett 

David Mizzen 

External Peer Reviewers 

Harold Brooks Dennis S. Mileti Sarah A. Rice 

Susan L. Cutter R. Shankar Nair Thomas W. Schmidlin 

Larry Griffis Eric K. Noji John T. Snow 

Jeremy Isenberg James R. Quiter Lawrence A. Twisdale 

Anne S. Kiremidjian Timothy A. Reinhold Peter J. Vickery 

NIST NCSTAR 3, Joplin Tornado Investigation v 
 

Contributors to the Investigation 

National Construction Safety Team Advisory Committee 

Ron J. Coleman Jeffrey L. Garrett James R. Quiter 

Paul A. Croce Jeremy Isenberg Sarah A. Rice 

Susan L. Cutter Anne S. Kiremidjian 

Carlos Fernandez–Pello R. Shankar Nair 

vi NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

ACKNOWLEDGEMENTS
	

The National Institute of Standards and Technology (NIST) would like to gratefully acknowledge the 

assistance of all who provided data and information in support of this investigation. NIST has received 

considerable cooperation and information from a variety of businesses, organizations, professional 

associations, and individuals representing building designers, building owners, utilities, media, disaster 

researchers, and disaster responders. NIST has also received considerable cooperation and information 

from citizens in the Joplin area, as well as from Federal, State, and local authorities. 

Local authorities providing information include the Joplin Public Works Department, the Joplin Police 

Department, the Joplin Fire Department, Joplin Schools, Joplin/Jasper County Emergency Management 

Agency, and Jasper County Geographic Information Services. State authorities providing information 

include the Missouri Department of Public Safety’s State Emergency Management Agency, the Missouri 

Department of Health and Senior Services, the Missouri State Highway Patrol, the Missouri Division of 

Fire Safety, the Oklahoma State Department of Health, and the Kansas Department of Health and 

Environment’s Office of Vital Statistics. Federal authorities providing information include the U.S. 

Army Corps of Engineers, the Federal Emergency Management Agency (FEMA), the National Oceanic 

and Atmospheric Administration’s National Weather Service (NWS), and the U.S. Department of Health 

and Human Services’ Centers for Disease Control and Prevention.

NIST has also received information from the American Red Cross; Mercy (the parent organization of St. 

John’s Regional Medical Center); GeoEye, Inc.; architectural and engineering design firms Allgeier, 

Martin and Associates, Inc., Heery International, Inc., and Patterson Latimer Jones Brannon Denham 

(PLJBD) Inc.; the Structural Engineers Association of Kansas and Missouri; the Missouri Structural 

Assessment and Visual Evaluation (SAVE) Coalition; utilities Empire District Electric Company and 

Missouri Gas Energy; and news and media companies KGCS-TV, KOAM-TV, Nexstar Broadcasting, 

Inc., KMXL-FM, Zimmer Radio, Inc., and The Joplin Globe. 

NIST would also like to thank FEMA, the National Oceanic and Atmospheric Administration, and 

National Science Foundation for their input to the report. 

NIST NCSTAR 3, Joplin Tornado Investigation vii 
 

Acknowledgements 

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viii NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

DEDICATION
	

On the evening of May 22, 2011, a powerful tornado struck southwestern Missouri. After the storm 

passed, the City of Joplin, which bore the brunt of the storm, was faced with decisions on how to rebuild a 

city that was not only damaged physically, but also emotionally, with the loss of 161 lives. Immediately 

after the storm hit, the construction, building, healthcare and public safety communities began asking a 

pressing question: How can we reduce our vulnerability, and increase our preparedness and safety, in 

such weather events? 

This investigation has, to the extent possible, reconstructed the characteristics of the tornado and the 

response of buildings, of lifelines, and of the people who found themselves in its path that fateful evening. 

The purpose was to make recommendations for improvements to building and emergency 

communications codes, standards and practices that lead to more tornado–resilient communities. For that 

reason, this report is dedicated to those lost in this tornado disaster, to those who have suffered from its 

impacts, and to those who will carry the findings of this report forward to improve the safety of people in 

future tornado disasters. 

NIST NCSTAR 3, Joplin Tornado Investigation ix 
 

Dedication 

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x NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

ABSTRACT
	

This is the final report of the National Institute of Standards and Technology (NIST) investigation of the 

May 22, 2011 tornado in Joplin, Missouri, conducted under the National Construction Safety Team Act. 

This report describes the wind field of the tornado and how the wind pressures and windborne debris 

damaged and destroyed thousands of buildings; the emergency communications before and during the 

tornado and how the public responded; the influence of tornado hazards and public response and building 

and designated shelter area performance on survival and injury; and areas of current building and 

emergency communications codes, standards and practices that warrant revision. 

Also described in this report is the means by which NIST reached its conclusions. NIST collected large 

numbers of documents, photographs, videos, and building plans; developed a computer model of the wind 

field of the tornado as it crossed the City of Joplin; analyzed the performance of a range of building types 

for life safety and functionality; interviewed many survivors of the tornado, developed an evidence–based 

explanation for decisions made and actions taken by the public in response to the tornado; and analyzed 

the factors affecting life safety outcomes. 

The report outlines 47 findings related to the May 22, 2011, Joplin tornado and concludes with a list of 16 

recommendations for action in areas of improved measurement and characterization of tornado hazards, 

new methods for tornado resistant design of buildings, enhanced guidance for community tornado 

sheltering, and improved and standardized emergency communications. 

Keywords: building performance, designated safe area, emergency communications, fatalities, injuries, 

Joplin Missouri, lifeline performance, structural collapse, tornado. 

NIST NCSTAR 3, Joplin Tornado Investigation xi 
 

Abstract 

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xii NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

TABLE OF CONTENTS
	

National Construction Safety Team for the NIST Technical Investigation of the May 22, 2011 

Tornado in Joplin, Missouri ......................................................................................................................... iii
 

List of Figures ............................................................................................................................................ xxi
 

List of Tables .......................................................................................................................................... xxxv
 

List of Acronyms and Abbreviations .................................................................................................... xxxvii
 

Metric Conversion Table ............................................................................................................................ xli
 

Executive Summary .................................................................................................................................. xliii
 

Contributors to the Investigation................................................................................................................... v
 

Acknowledgements ..................................................................................................................................... vii
 

Dedication .................................................................................................................................................... ix
 

Abstract ........................................................................................................................................................ xi
 

Table of Contents ....................................................................................................................................... xiii
 

E.1 Introduction.................................................................................................................................. xliii
 

E.2 NIST Reponse and Scope of the Technical Investigation ............................................................ xliv
 

E.3 The Hazard Context ..................................................................................................................... xlvi
 

E.4 Principal Findings ....................................................................................................................... xlvii
 

E.4.1 Context for Findings........................................................................................................ xlvii
 

E.4.2 Findings of the Technical Investigation ......................................................................... xlviii
 

E.5 Recommendations....................................................................................................................... xlvii
 

Chapter 1
 

Introduction................................................................................................................................................... 1 

1.1 The City of Joplin ............................................................................................................................ 1 

1.2 The Event ......................................................................................................................................... 6 

1.3 The Toll.......................................................................................................................................... 19
 

1.4 NIST’s Joplin Tornado Investigation............................................................................................. 19 

1.4.1 Goals................................................................................................................................... 20 

NIST NCSTAR 3, Joplin Tornado Investigation xiii 
 

 

 

 

 

 

 

 

 

Table of Contents 

1.4.2 Objectives ........................................................................................................................... 21 

Chapter 2
 

Tornado Hazard Characteristics .................................................................................................................. 23 

2.1 Introduction.................................................................................................................................... 23 

2.2 Meteorological Conditions............................................................................................................. 23 

2.2.1 Objective ............................................................................................................................ 23 

2.2.2 Joplin Environment and Timeline ...................................................................................... 23 

2.3 Near–Surface Wind Environment .................................................................................................. 30 

2.3.1 Objective ............................................................................................................................ 30 

2.3.2 Tornado Wind-Field Regions ............................................................................................. 30 

2.3.3 Direct Wind Speed Observations ....................................................................................... 33 

2.3.3.1 Wind Environment .............................................................................................. 33 

2.3.4 Indirect Wind Speed Estimation ......................................................................................... 34 

2.3.4.1 Observed Damage (EF Scale) .............................................................................. 34 

2.3.4.2 Tornado Wind Field Model ................................................................................. 39 

2.4 Description of the Tornado Hazard in the United States ............................................................... 56 

2.4.1 Objective ............................................................................................................................ 56 

2.4.2 Tornado Climatology ......................................................................................................... 56
 

2.4.2.1 NOAA Tornado Database ................................................................................... 56
 

2.4.2.2 Tornado–Induced Losses ..................................................................................... 57 

2.4.2.3 Tornado Hazard Analysis .................................................................................... 58 

2.4.3 Urbanization of Communities ............................................................................................ 67
 

2.5 Enhanced Fujita Scale Assessment ................................................................................................ 68 

2.5.1 Objective ............................................................................................................................ 68 

2.5.2 History ................................................................................................................................ 68 

2.5.3 Current Practice/Guidance.................................................................................................. 68 

2.5.4 Recent Observations Using the EF Scale ........................................................................... 69 

2.6 Summary ........................................................................................................................................ 70 

2.6.1 Meteorological Conditions ................................................................................................. 70 

xiv NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

Table of Contents 

2.6.2 Near–Surface Wind Environment ...................................................................................... 70 

2.6.3 Description of the U.S. Tornado Hazard ............................................................................ 71
 

2.6.4 Enhanced Fujita Scale Assessment .................................................................................... 72 

2.7 References...................................................................................................................................... 73 

Chapter 3
 

Performance of Buildings, Designated Safe Areas, and Lifelines .............................................................. 77 

3.1 Introduction.................................................................................................................................... 77 

3.1.1 Overall Extent of Damage .................................................................................................. 77 

3.1.2 Scope of Structures Surveyed and of this Chapter ............................................................. 79 

3.1.3 Methodology for Building Performance Evaluation .......................................................... 85 

3.1.4 Tornado Design: A National Perspective .......................................................................... 86 

3.1.5 History of Building Code Adoption in Joplin .................................................................... 89 

3.2 Performance of Buildings .............................................................................................................. 91 

3.2.1 Critical Facilities and High–Occupancy Buildings ............................................................ 92 

3.2.1.1	 St. John’s Regional Medical Center .................................................................... 92 

3.2.1.2	 Walmart ............................................................................................................. 120 

3.2.1.3	 Home Depot....................................................................................................... 129 

3.2.1.4	 Joplin East Middle School ................................................................................. 139 

3.2.1.5	 Joplin High School ............................................................................................ 151 

3.2.1.6	 Franklin Technology Center .............................................................................. 159 

3.2.1.7	 St. Mary’s Catholic Elementary School ............................................................ 164 

3.2.1.8	 Summary of Performance of Critical Facilities and High–Occupancy
 

Buildings............................................................................................................ 167 

3.2.2 Commercial Buildings...................................................................................................... 169
 

3.2.2.1	 Ozark Center for Autism ................................................................................... 169 

3.2.2.2	 St. Paul’s United Methodist Church .................................................................. 175 

3.2.2.3	 Ramesh Shah Ophthalmologist ......................................................................... 179 

3.2.2.4	 Summary of Performance of Commercial Buildings ........................................ 183 

3.2.3 Residential Buildings ....................................................................................................... 184 

NIST NCSTAR 3, Joplin Tornado Investigation xv 
 

 

 

 

 

 

 

Table of Contents 

3.2.3.1 Multi–Family Residential Buildings ................................................................. 185 

3.2.3.2 Single–Family Residential Buildings ................................................................ 197 

3.2.3.3 Summary of Performance of Residential Buildings .......................................... 203 

3.3 Performance of Designated Safe Areas and Shelters ................................................................... 203 

3.3.1 Commercial High–Occupancy Facilities.......................................................................... 205 

3.3.1.1 Designated Refuge Area at Walmart ................................................................. 205
 

3.3.1.2 Designated Refuge Area at the Home Depot..................................................... 206 

3.3.2 Schools ............................................................................................................................. 210 

3.3.2.1 Designated Safe Areas at Joplin East Middle School........................................ 210 

3.3.2.2 Designated Refuge Areas at Joplin High School ............................................... 210 

3.3.3 High–Occupancy Health Care Facilities .......................................................................... 213 

3.3.3.1 Designated Refuge Areas at Ozark Center for Autism ...................................... 213
 

3.3.3.2 Designated Refuge Areas at SJRMC ................................................................. 215 

3.3.3.3 Designated Refuge Areas at the Greenbriar Nursing Home .............................. 217 

3.3.4 In–Home Shelters ............................................................................................................. 217
 

3.3.4.1 In–Home Steel Shelter ....................................................................................... 219 

3.3.4.2 In–Home Kevlar® –Reinforced Shelter .............................................................. 219 

3.3.5 Summary of Performance of Shelters/Designated Refuge Areas ..................................... 219 

3.4 Performance of Lifelines as Related to Building Functionality ................................................... 222 

3.4.1 Overall Tornado Effect on Lifelines in Joplin .................................................................. 222 

3.4.1.1 Electricity .......................................................................................................... 222
 

3.4.1.2 Water ................................................................................................................. 224 

3.4.1.3 Natural Gas ........................................................................................................ 226 

3.4.1.4 Communications ................................................................................................ 226 

3.4.2 Effect of Lifeline Disruptions on Building Operations .................................................... 228 

3.4.3 Summary of Performance of Lifelines ............................................................................. 231
 

3.5 References.................................................................................................................................... 232 

Chapter 4
 

Emergency Communications, Public Response, and Tornado Deaths and Injuries ................................. 235 

xvi NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

Table of Contents 

4.1 Public Warning Response in Disasters ........................................................................................ 235 

4.2 Data Collection ............................................................................................................................ 237 

4.2.1 Data on Public Response .................................................................................................. 238 

4.2.2 Data on Consequences of the Tornado—Injuries and Deaths .......................................... 240
 

4.2.3 Data on Emergency Response .......................................................................................... 242 

4.3 Joplin, Missouri, Before the Tornado of May 22, 2011 ............................................................... 242 

4.3.1 Emergency Communications—Outdoor Siren Systems................................................... 243 

4.3.2 Emergency Communications—Other Modes of Communication.................................... 246 

4.3.3 Sheltering Procedures for Tornadoes ............................................................................... 247 

4.3.4 Tornado History in the Joplin Area .................................................................................. 248 

4.4 Joplin, Missouri, on May 22, 2011—The Tornado Hits .............................................................. 250 

4.4.1 Elks Lodge........................................................................................................................ 256 

4.4.2 St. John’s Regional Medical Center ................................................................................. 256 

4.4.3 Stained Glass Theater ....................................................................................................... 261 

4.4.4 Greenbriar Nursing Home ................................................................................................ 263 

4.4.5 Places of Worship............................................................................................................. 265 

4.4.6 AT&T Store...................................................................................................................... 268 

4.4.7 Home Depot ..................................................................................................................... 270 

4.4.8 Pizza Hut .......................................................................................................................... 272 

4.4.9 Walmart Store #59............................................................................................................ 274 

4.4.10 Single–Family Homes and Apartment Complexes .......................................................... 277
 

4.4.11 In Vehicles or Outdoors.................................................................................................... 287 

4.4.12 Additional Locations of Fatalities in Joplin ..................................................................... 292 

4.5 Casualties from the May 22, 2011, Joplin Tornado ..................................................................... 292 

4.5.1 Settings in Which Fatalities Occurred .............................................................................. 293
 

4.5.2 Basic Causes of Deaths and Injuries ................................................................................ 293
 

4.5.3 Date of Death.................................................................................................................... 294
 

4.5.4 Demographics................................................................................................................... 295 

4.5.4.1 Gender ............................................................................................................... 295 

NIST NCSTAR 3, Joplin Tornado Investigation xvii 
 

 

 

Table of Contents 

4.5.4.2	 Age—Deaths ..................................................................................................... 295 

4.5.4.3	 Age—Injuries .................................................................................................... 298
 

4.5.5 Summary Questions and Findings Related to Casualties ................................................. 298 

4.6 The Influence of Environmental Conditions on Casualties ......................................................... 299 

4.6.1 The Influence of Environmental Conditions on Casualties Outside of Buildings............ 303 

4.6.2 The Influence of Environmental Conditions on Casualties Inside of Buildings .............. 307 

4.6.2.1	 Non–Residential Structures ............................................................................... 309 

4.6.2.2	 Residential Buildings......................................................................................... 319 

4.6.3 Summary .......................................................................................................................... 323
 

4.7 The Influence of Emergency Communications and Public Response on Casualties Both 

Inside and Outside of Buildings ................................................................................................... 325 

4.7.1 Protection Is Unnecessary ................................................................................................ 329 

4.7.1.1	 No General Risk Perceived................................................................................ 329 

4.7.1.2	 No Personal Risk Perceived (“It Will Not Happen to Me”) .............................. 332 

4.7.2 Protective Action is Necessary ......................................................................................... 336 

4.7.2.1	 Confirmation is Achieved After Initial Warnings ............................................. 336 

4.7.2.2	 Personal Risk is Perceived................................................................................. 337 

4.7.2.3	 Other Actions During Decision Making ............................................................ 338 

4.7.3 Other Important Factors Related to Casualties ................................................................. 338
 

4.8 Chapter Summary ........................................................................................................................ 339 

4.9 References.................................................................................................................................... 342 

Chapter 5
 

Findings and Recommendations ............................................................................................................... 349 

5.1 Principal Findings ........................................................................................................................ 349 

5.1.1 Context for Findings ......................................................................................................... 349 

5.1.2 Findings Related to Tornado Hazard Characteristics and Associated Wind Field ........... 350 

5.1.2.1	 Measurements of the Near–Surface Wind Field in Tornadoes ......................... 350 

5.1.2.2	 Assessment of Tornado Climatology, Hazard, and Risk for Structural
 

Design ................................................................................................................ 351
 

5.1.2.3	 Limitations of the Enhanced Fujita (EF) Scale.................................................. 351 

xviii NIST NCSTAR 3, Joplin Tornado Investigation 
Table of Contents 

5.1.3	 Findings Related to the Response of Residential, Commercial, and Critical
 

Buildings, Including the Performance of Designated Safe Areas and of Lifelines
 

Pertaining to the Continuity of Building Operations ........................................................ 351 

5.1.3.1 Building Performance........................................................................................ 351 

5.1.3.2 Performance of Shelters/Safe Rooms/Designated Refuge Areas ...................... 353 

5.1.3.3 Performance of Lifelines ................................................................................... 354 

5.1.4	 Findings Related to the Pattern, Location, and Cause of Fatalities and Injuries, and 

Associated Performance of Emergency Communications Systems and Public
 

Response........................................................................................................................... 354 

5.1.4.1 Emergency Communication Prior to May 22, 2011 .......................................... 355 

5.1.4.2 Tornado History Prior to May 22, 2011 ............................................................ 355 

5.1.4.3 Emergency Communication on May 22, 2011 .................................................. 355 

5.2 Recommendations........................................................................................................................ 357 

5.2.1	 Recommendations Related to Tornado Hazard Characteristics and Associated Wind 

Field.................................................................................................................................. 358 

5.2.2	 Recommendations Related to the Performance of Buildings, Shelters/Designated 

Safe Areas, and Lifelines.................................................................................................. 361 

5.2.3	 Recommendations Related to the Pattern, Location, and Cause of Fatalities and 

Injuries, and Associated Performance of Emergency Communications Systems and 

Public Response ............................................................................................................... 367 

Appendix A
 

Mesoscale Discussions Issued on May 22, 2011, That Included Joplin ................................................... 371 

A.1 Mesoscale Discussion 853 ........................................................................................................... 371
 

A.2 Mesoscale Discussion 862 ........................................................................................................... 372
 

A.3 Mesoscale Discussion 867 ........................................................................................................... 373
 

Appendix B
 

EF–Scale Rating for Random Residential Structures ............................................................................... 375 

Appendix C
 

Model Grid Coordinates ........................................................................................................................... 377 

Appendix D
 

Tornado Wind Field Model ...................................................................................................................... 379 

Appendix E
 

Modeled Wind Speed and Direction Time Histories at Select Locations ................................................. 387 

NIST NCSTAR 3, Joplin Tornado Investigation xix 
 

 

 

 

 

 

 

 

Table of Contents 

Appendix F
 

Tornadoes per Year Maps (EF-0 Through EF-5)...................................................................................... 393 

Appendix G
 

History of Code Adoptions by the City of Joplin ..................................................................................... 397 

Appendix H
 

Estimated Design Wind Pressure and Strengths of Connections of Joplin Walmart Building #59 .......... 403 

H.1 Estimated Design Wind Pressure Based on IBC 2000 ................................................................. 403 

H.2 Estimated Uplift Strength Of Roof Joist–to–Joist Girder Connections ....................................... 404 

Appendix I
 

Estimated Design Wind Pressure and Strengths of Connections of Joplin Home Depot Building .......... 405 

I.1 Estimated Design Wind Pressure Based on BOCA NBC/1996................................................... 405
 

I.2 Roof Bracing Forces RT ......................................................................................................................................................................... 407
 

I.3 Roof Diaphragm Shear and Stiffness .......................................................................................... 409 

I.4 Uplift and Shear Capacities of Roof Deck–to–Joist Connections ............................................... 410 

Appendix J
 

Estimated Design Wind Pressure for Joplin East Middle School Gymnasium......................................... 413 

Appendix K
 

Qualitative Analysis of the Current State of Tornado Warning Systems in the U.S. ............................... 415 

Appendix L 

U.S. Codes and Standards on Outdoor Warning Systems ........................................................................ 419 

Appendix M
 

NOAA/NWS Warning Text for the Joplin Tornado ................................................................................. 423 

M.1 Warning Issued at 5:09 PM CDT ................................................................................................ 423
 

M.2 Warning Issued at 5:17 PM CDT ................................................................................................ 424 

Appendix N
 

Methods for Development of Evidence-Based Explanation of Decision-Making in Joplin Tornado ...... 427 

xx NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

LIST OF FIGURES
	

Figure 1–1. Location of Joplin (circled in red) in southwestern Missouri ................................. ........... 1 

Figure 1–2. Map of Joplin and surrounding area. .................................................................................. 2 

Figure 1–3. Damage from the 1971 Joplin tornado................................................................................ 5 

Figure 1–4. Initial damage in the Joplin tornado. Yellow arrows indicate directions of tree fall. 

Possible multiple vortices shown by red arrows. ................................................................ 8 

Figure 1–5. Damage on the west side of Joplin. .................................................................................... 9 

Figure 1–6. Aerial photo showing damage to SJRMC and the surrounding area. ............................... 11 

Figure 1–7. Aerial photo showing locations of the Ozark Center, Greenbriar Nursing Home, St. 

Mary’s Catholic Elementary School, and EDE substation 59 (from west to east). 

Residential area is outlined in white. ................................................................................ 13 

Figure 1–8. Aerial photo showing the locations of a heavily damaged residential area, Franklin 

Technology Center, Joplin High School, and Harmony Heights Baptist Church. The 

color of each building footprint shows the level of damage to that structure. .................. 14 

Figure 1–9. Aerial photo of damaged residential areas (including apartment complexes) in Joplin
 

near the intersection of 20th Street and Connecticut. ....................................................... 15 

Figure 1–10.	 Aerial photo showing damage to a commercial area on the eastern side of Joplin near
 

the intersection of Range Line Road and 20th Street........................................................ 16 

Figure 1–11.	 Aerial photo of damage to a residential area and Joplin East Middle School................... 18 

Figure 2–1. 500 millibar (mb) analysis at 7 a.m. CDT (1200 Coordinated Universal Time (UTC))
 

on May 22, 2011. .............................................................................................................. 24 

Figure 2–2. Surface analysis at 7 p.m. CDT (0000 UTC, May 23, 2011) on May 22, 2011. .............. 24 

Figure 2–3. Wind shear and CAPE for severe thunderstorm environments. "Best Discriminator"
 

line denotes areas to right and above as being more favorable for significant severe 

thunderstorms.................................................................................................................... 25 

Figure 2–4. Tornado outlook issued by NOAA’s Storm Prediction Center at 1 a.m. CDT (0600 

UTC) on May 22, 2011. .................................................................................................... 26
 

Figure 2–5. Tornado warnings issued by the Springfield NWS office on May 22, 2011. Zulu time,
 

or Z, in the figure is the same as UTC time (Z = UTC). Estimated NWS track of the 

Joplin tornado shown outlined in brown........................................................................... 27 

Figure 2–6. Timeline of watches, warnings, sirens, and the tornado itself. ......................................... 27 

NIST NCSTAR 3, Joplin Tornado Investigation xxi 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

List of Figures 

Figure 2–7. Radar reflectivity sequence from the Springfield radar. Radar reflectivity is the right
 

panel and radial velocity is the left panel of each image. For radial velocity, red to
 

yellow colors indicate winds receding from the radar (which is located to the east of
 

Joplin), green to white colors indicate winds approaching the radar. These colors in 

close proximity suggest rotation and signify the approximate tornado position. A
 

"hook echo" is seen in reflectivity images, also a possible indication of a tornado. 

These features are annotated in the 2248 UTC panel. ...................................................... 29 

Figure 2–8. Center of Joplin tornado track as estimated by NIST ....................................................... 30 

Figure 2–9. General tornado flow regions............................................................................................ 31 

Figure 2–10.	 Normalized Rankine vortex showing maximum wind speed at RMW (φ=1.0). ............. 32 

Figure 2–11.	 Generalized wind vector for a point denoted by the small gray circle. RMW is 

distance from gray circle to “tornado center.” .................................................................. 32 

Figure 2–12.	 Time history of mean and gust wind speed and mean wind direction from the Joplin 

ASOS station (KJLN) from 5 p.m. to 6 p.m. CDT (2200–2300 UTC), on May 22, 

2011. Boxed area is approximate time when the tornado was on the ground in Joplin ... 33
 

Figure 2–13.	 Aerial photo of Walmart Store #59 showing extensive damage to the southern
 

(bottom) half of the building ............................................................................................. 35 

Figure 2–14.	 Elevation view of southwest–facing wall of Walmart Store #59...................................... 36 

Figure 2–15.	 Building footprints in part of Joplin showing damage classes. St. Mary’s Catholic
	

Elementary School (red box) shown for reference. Area shown is approximately 1.0 

miles west to east and 0.8 miles north to south................................................................. 38 

Figure 2–16.	 Grid system for tree fall analysis in Joplin. Each dot denotes a tree/wind–field point
 

spaced at every 0.05 miles. The grid extends 6.2 miles west to east and 2.0 miles north 

to south.............................................................................................................................. 42 

Figure 2–17.	 Grid overlaid with Rankine vortex model results. Red arrows represent current wind 

direction, black arrows represent direction of tree fall, and contouring illustrates wind 

speed field. ........................................................................................................................ 44 

th nd Figure 2–18.	 Observed tree fall pattern between 20 and 32 streets just east of Schifferdecker
 

Ave. Area is approximately 0.5 miles west to east by 1.0 miles north to south ............... 45 

Figure 2–19.	 Example of procedure for comparing observed tree fall to modeled tree fall. Output
 

parameters are also listed .................................................................................................. 47
 

Figure 2–20.	 Ranges and best estimate of wind speed (left) and associated wind direction (right)
 

for Grid Point #1175 (southwest corner of W. 26th St. and S. Jackson Ave). Best
 

estimates are the bold traces on each plot ......................................................................... 48 

Figure 2–21.	 Translation direction (θT) changes in the Joplin tornado. Numbers are approximate 

directions in degrees. White line indicates estimated center of tornado path. The area
 

in the figure is approximately 6.2 miles west to east and 2.0 miles north to south........... 48 

xxii NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

List of Figures 

Figure 2–22.	 Example of a modeled best estimate of tornado wind speed and direction time history
 

for Grid Point #1175 (southwest corner of W. 26th St. and S. Jackson Ave)................... 49 

Figure 2–23.	 Estimated maximum wind speed grid points from tornado wind field model grid
 

points grouped by EF Scale. The solid black line represents the estimated tornado 

center. The area in the figure is approximately 6.2 miles west to east and 2.0 miles
 

north to south .................................................................................................................... 50 

Figure 2–24.	 Estimated maximum wind speed polygons from tornado wind field model grouped by
 

EF Scale. The solid black line represents the estimated tornado center. The area in the 

figure is approximately 6.2 miles west to east and 2.0 miles north to south. ................... 50 

Figure 2–25.	 Illustration of differences in Rankine vortex model given φ parameter ........................... 51 

Figure 2–26.	 Best estimate of duration of wind speeds greater than or equal to EF–2 (≥ 110 mph). 

Green line shows estimated tornado center. The area in the figure is approximately 6.2 

miles west to east and 2.0 miles north to south................................................................. 51 

Figure 2–27.	 Three distinct ranges of maximum wind speed based on different values of translational
 

speed (VT) for Grid Point #1175. Red dots illustrate the combinations of V using the 

range values of VT and Gmax.............................................................................................. 53 

Figure 2–28.	 Average fatalities per tornado and total fatalities by EF number for the period of
 

1950–2011 ........................................................................................................................ 57 

Figure 2–29.	 Average loss per tornado and total loss by EF number for the period of 1995 – 2011 

(2011 dollars) .................................................................................................................... 58 

Figure 2–30.	 Illustration of point–based probability approach. ............................................................. 59 

Figure 2–31.	 Example of spatially based approach within a given region. ............................................ 62 

Figure 2–32.	 Probability density function of EF–2 or stronger tornadoes. Black dots represent
 

individual touchdown locations. Warmer colors represent higher probability and 

probability values are shown on contour lines .................................................................. 64 

Figure 2– 33. Probability density of EF–2 or greater tornadoes from 1980 through 2011 with EF–2
 

or stronger tornadoes per year values shown at each grid point. ...................................... 65 

Figure 2– 34. Illustration of spatially based analysis. Contoured values are return period (MRI) in 

years for EF–2 or stronger tornadoes ................................................................................ 67 

Figure 3–1. Westernmost (earliest) segment of the tornado path through Joplin, showing locations
 

of facilities surveyed by NIST relative to the estimated center line of the tornado damage 

path (red solid line). The color coded building footprints indicate the estimated level
 

of damage to individual structures (see legend above) ..................................................... 82 

Figure 3–2. Central segment of the tornado path through Joplin, showing locations of facilities 

surveyed by NIST relative to the estimated center line of the tornado damage path (red 

NIST NCSTAR 3, Joplin Tornado Investigation xxiii 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

List of Figures 

solid line). The color coded building footprints indicate the estimated level of damage 

to individual structures (see legend above)....................................................................... 83 

Figure 3–3. Easternmost segment of the tornado path through Joplin, showing locations of facilities 

surveyed by NIST relative to the estimated center line of the tornado damage path 

(red solid line). The color coded building footprints indicate the estimated level of 

damage to individual structures (see legend above) ......................................................... 84 

Figure 3–4. Regionalization of tornado wind hazard ........................................................................... 88 

Figure 3–5. Tornado hazard map for shelter and safe–room design .................................................... 89 

Figure 3–6. Overview of St. John’s Regional Medical Center............................................................. 93 

Figure 3–7. Estimated time–history of wind speed and direction near the north end of SJRMC ........ 95 

Figure 3–8. Estimated time–history of wind speed and direction near the south end of SJRMC ........ 95 

Figure 3–9. SJRMC's West Tower (north side). .................................................................................. 96 

Figure 3–10. Intact windows on fifth floor of SJMRC’s West Tower (south side). .............................. 98 

Figure 3–11. Intact windows on fifth floor of SJMRC’s West Tower (north side). .............................. 98 

Figure 3–12. Damage to roof and penthouse walls of SJMRC’s West Tower....................................... 99 

Figure 3–13. Typical damage to the interior of SJMRC’s West Tower............................................... 100 

Figure 3–14. View from southwest of SJMRC’s East Tower showing that most windows on south 

and west sides of building and curtain walls on connecting elevator steel frame have 

broken ............................................................................................................................. 102 

Figure 3–15. View from southeast of SJMRC’s East Tower showing that most windows on south 

and east sides of building have broken ........................................................................... 102 

Figure 3–16. Close–up view showing minor damage to architectural precast concrete column–
	

cover–and–spandrel system and significant damage to glass windows of SJMRC’s 

East Tower. ..................................................................................................................... 103 

Figure 3–17. Missing/collapsed vertical insulated metal curtain wall panels of SJMRC’s East
 

Tower penthouse ............................................................................................................. 104 

Figure 3–18. Damage to roof covering system of SJMRC’s East Tower (peeling–off of EPDM 

roof membrane and rigid insulation, loss/displacement of roof aggregate ballast) ........ 105 

Figure 3–19. Overview of West, East, and Elevator Towers and Oncology Clinic Building showing
 

that most of the aggregates that were used as roof ballast on these buildings are 

missing ............................................................................................................................ 106 

xxiv NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

List of Figures 

Figure 3–20.	 View from northwest of Emergency Generator Building. Note northward and eastward 

direction of wall failure, consistent with the direction of maximum wind (westerly)
 

shown on Fig. 3–7........................................................................................................... 107 

Figure 3–21.	 East side of Emergency Generator Building. Note eastward direction of failure on east
 

wall (CMU wall falling outward, door opened, louver pushed outward). Also note 

louver on north wall pushed outward, consistent with direction of maximum westerly
 

wind and indicative of high internal pressure ................................................................ 107 

Figure 3–22.	 Failure details at Emergency Generator Building ........................................................... 108
 

Figure 3–23.	 Views of damage sustained at the Chiller Plant.............................................................. 111 

Figure 3–24.	 South elevation of Oncology Clinic Building showing damage to building envelope 

(broken glass windows, missing window frame, missing roof decks)............................ 113 

Figure 3–25.	 Roof of Oncology Clinic Building: missing steel deck panels, gypsum board, rigid
 

insulation, membrane, and aggregate ballast .................................................................. 113 

Figure 3–26.	 Roof of Oncology Clinic Building: failed puddle welds connecting roof deck with
 

supporting roof beam ...................................................................................................... 113 

Figure 3–27.	 In Oncology Clinic Building, interior damage to ductwork, electrical wiring, 

suspended ceiling, interior partition/metal stud wall, furniture. Note the aggregate
 

from roof in the interior. ................................................................................................. 114 

Figure 3–28.	 View of damage to envelope of Medical Office Building 1 ........................................... 115 

Figure 3–29.	 Views of (top) damage to envelope of Medical Office Building 2 and (bottom)
 

portion of the steel frame system (bolted beam–column connection) ............................ 117 

Figure 3–30.	 Evidence of debris impact causing breakage of windows at Medical Office
 

Building 2 ....................................................................................................................... 118
 

Figure 3–31.	 Roof aggregate ballast became wind–borne debris (on ground by Medical Office
 

Building 2) ...................................................................................................................... 118 

Figure 3–32.	 Collapse of an entire brick veneer curtain wall and the supporting aluminum stud 

frame on the south–facing wall of Physician’s Office Building ..................................... 119 

Figure 3–33.	 Aerial views of Walmart in relation to the tornado damage path (red line denotes
 

center of damage path) .................................................................................................... 121 

Figure 3–34.	 Aerial view of Walmart outlining southern half of building collapsed by the tornado .. 122 

Figure 3–35.	 Estimated time–history of wind speed and direction near the northeast corner of
 

Walmart .......................................................................................................................... 123 

Figure 3–36.	 Estimated time–history of wind speed and direction near the southeast corner of
 

Walmart .......................................................................................................................... 123 

NIST NCSTAR 3, Joplin Tornado Investigation xxv 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

List of Figures 

Figure 3–37.	 Roof system (decks and joists) missing at Walmart. Some roof joists displaced 

upward (top chords used to be at same elevation as top chords of joist girders, but
 

now sitting above joist girders), showing evidence of wind uplift action as primary
 

cause of failure ................................................................................................................ 126 

Figure 3–38.	 Large area of roof system shown missing at Walmart. Joist girders bent upward due 

to uplift pressure ............................................................................................................. 126 

Figure 3–39.	 Missing door and glass panels and damage to signage at south entrance of Walmart
 

on west wall (envelope failure allowing air infiltration to the interior and causing
 

increased wind uplift) ..................................................................................................... 127 

Figure 3–40.	 Collapsed east wall of Walmart due to loss of roof lateral bracing and inward wind 

pressure ........................................................................................................................... 129 

Figure 3–41.	 Typical loading and design conditions for BTS building and possible failure mode ..... 130 

Figure 3–42.	 Aerial views of Home Depot in relation to the tornado damage path (red line denotes
 

center of damage path) .................................................................................................... 131 

Figure 3–43.	 Estimated time–history of wind speed and direction near the southeast corner of
 

Home Depot .................................................................................................................... 132 

Figure 3–44.	 Typical connection between the roof system and the perimeter tilt–up RC wall at
 

Home Depot .................................................................................................................... 133 

Figure 3–45.	 Typical connection between roof joist girder and interior column at Home Depot........ 133 

Figure 3–46.	 Positive wall–to–footing connection (dowels connection to footing and concrete 

block, in 9 tilt–up wall panels near loading dock) at Home Depot ................................. 135 

Figure 3–47.	 Friction–only wall–to–footing connection (in remaining 64 tilt–up RC wall panels)
 

at Home Depot ................................................................................................................ 135 

Figure 3–48.	 Roof framing schedule and typical roof joist–to–wall panel welded connection at
 

Home Depot .................................................................................................................... 135 

Figure 3–49.	 Collapsed Home Depot building (view from the northwest). Note the loss of all roof
 

decks and upward displacement of joists and joist–girders. ........................................... 137 

Figure 3–50.	 Ten tilt–up panels in the northeast corner of the Home Depot remained standing. Seven 

of these 10 panels had positive connections to the footing and thus some degree of
 

restraint against rotation. The other three uncollapsed panels had friction–only
 

connections to the footing but appeared to have been supported against falling
 

outward by steel shelving on the exterior side (Garden Center) ..................................... 137 

Figure 3–51.	 Damaged joist girders and interior columns at Home Depot. Note the complete loss
 

of the roof system that was connected to the girders. ..................................................... 138 

Figure 3–52.	 Aerial views of Joplin East Middle School in relation to the tornado damage path 

(red line denotes center of damage path). ....................................................................... 140 

xxvi NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

List of Figures 

Figure 3–53.	 Center diagram shows the sections of the Joplin East Middle School building complex. 

The Gymnasium (A) and Auditorium (B) sustained the greatest damage in the 

tornado. ........................................................................................................................... 141 

Figure 3–54.	 Estimated time–history of wind speed and direction near the south end of Joplin 

East Middle School (over the Gymnasium) .................................................................... 142 

Figure 3–55.	 Lateral bracing for Joplin East Middle School Gymnasium walls. ................................ 144 

Figure 3–56.	 Joplin East Middle School Gymnasium building, viewed from the west, showing
 

complete loss of steel roof deck, disconnection and collapse of the first two bow–
	

string steel trusses, and collapse of 9 out of 11 tilt–up panels of the west wall.............. 144 

Figure 3–57.	 Disconnection of steel roof deck of Joplin East Middle School Gymnasium due to 

failure of puddle welds due to uplift pressure. ................................................................ 145 

Figure 3–58.	 Collapsed bow–string roof trusses and collapsed west wall tilt–up panels in the 

interior of the Joplin East Middle School Gymnasium. .................................................. 146 

Figure 3–59.	 Seat angle welded to end of bow–string roof truss and embedded into top of tilt–up panel
 

got disconnected at the Joplin East Middle School Gymnasium. Note missing vertical
 

headed studs (4, each 10 in. long), which appeared to have been sheared off from the 

angle. The three horizontal studs remained connected to the seat angle but pulled
 

out from the concrete. ..................................................................................................... 146 

Figure 3–60.	 Elevation showing first two bow–string roof trusses and collapse radius of west
 

wall at Joplin East Middle School Gymnasium. ............................................................. 148 

Figure 3–61.	 View from east of Joplin East Middle School Auditorium building. ............................. 150 

Figure 3–62.	 In the wreckage of the Joplin East Middle School Auditorium, missing roof deck
 

from top of joist—only puddle–weld marks remained. .................................................. 150
 

Figure 3–63.	 Collapse due to overturning (outward) of east perimeter Joplin East Middle School
 

Auditorium wall after loss of roof diaphragm. ............................................................... 151 

Figure 3–64.	 Overview of Joplin High School complex, with estimated center line of Joplin
 

tornado damage path shown in red. ................................................................................ 152 

Figure 3–65.	 Estimated time–history of wind speed and direction near the southeast corner
 

(closest to center of tornado damage path) of Joplin High School ................................. 153 

Figure 3–66.	 View from the exterior showing damage to the envelope of one of the RC frame 

buildings (east building) of Joplin High School. ............................................................ 154 

Figure 3–67.	 View from the exterior showing damage to the envelope of one of the RC frame 

buildings (west building) of Joplin High School. ........................................................... 154 

Figure 3–68.	 Damage and debris in an interior hallway of Joplin High School .................................. 155 

NIST NCSTAR 3, Joplin Tornado Investigation xxvii 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

List of Figures 

Figure 3–69. View from west of the Joplin High School Gymnasium building .................................. 156
 

Figure 3–70. View from north of the Joplin High School Auditorium building. ................................. 157 

Figure 3–71. Failure of joist–to–CMU wall connection due to uplift at Joplin High School. ............. 157 

Figure 3–72. Collapse of CMU wall due to loss of lateral roof bracing at Joplin High School ........... 158 

Figure 3–73. Short anchorage between CMU wall and concrete footing at Joplin High School......... 158 

Figure 3–74. Overview of damage at Franklin Technology Center, with center line of tornado
 

damage path (in red) ....................................................................................................... 160 

Figure 3–75. Estimated time–history of wind speed and direction near the southeast corner of
 

Franklin Technology Center ........................................................................................... 161 

Figure 3–76. Steel roof deck and roof joist connection to CMU wall bond beam at Franklin 

Technology Center .......................................................................................................... 161 

Figure 3–77. Steel roof joists, with missing roof decks, remained connected to CMU bond beam. 

Bond beam remained continuous, but was disconnected from the CMU walls along the 

bond line between the two CMU courses at the top of the Franklin Technology 

Center wall ...................................................................................................................... 162 

Figure 3–78. Perimeter CMU wall that collapsed after loss of roof lateral bracing at the Franklin 

Technology Center (note lack of reinforcing dowels connecting wall to concrete 

footing)............................................................................................................................ 163 

Figure 3–79. Another perimeter wall failure at the Franklin Technology Center (again, note lack
 

of reinforcing dowels connecting wall to concrete footing). .......................................... 163 

Figure 3–80. Overview of damage at St. Mary’s Catholic Elementary School, with estimated 

center line of tornado damage path shown in red. .......................................................... 165 

Figure 3–81. Estimated time–history of wind speed and direction near the northeast corner of
 

St. Mary’s Catholic Elementary School.......................................................................... 166 

Figure 3–82. Section of building at St. Mary’s Catholic Elementary school with complete loss
	

of the steel roof system. .................................................................................................. 166 

Figure 3–83. Section of building at St. Mary’s Catholic Elementary school with collapsed 

perimeter CMU walls...................................................................................................... 167 

Figure 3–84. Overview of damage to the Ozark Center and surrounding buildings, with 

estimated center line of tornado damage path shown in red. .......................................... 170 

Figure 3–85. Estimated time–history of wind speed and direction near the southwest corner of
 

the Ozark Center ............................................................................................................. 171 

Figure 3–86. Ozark Center building (viewed from the southeast). ...................................................... 172 

xxviii NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

List of Figures 

Figure 3–87.	 Interior view of the physical education section of the Ozark Center showing structural
 

system with roof truss–column moment connection and open–web roof joist and 

wide–rib steel roof deck.................................................................................................. 172 

Figure 3–88.	 Significant damage to the envelope and minor damage to the MWFRS of the physical
 

education section of the Ozark Center building, including (1) loss of part of steel roof
 

decks, (2) loss of all insulating windows and steel frames on all wind–exposed sides, 

and (3) deformation of steel beam (likely due to debris impact) .................................... 174 

Figure 3–89.	 Typical damage to the Ozark Center building envelope (broken window glazing, 

missing window frames, and torn exterior steel panels) ................................................. 174 

Figure 3–90.	 Overview of damage at St. Paul’s United Methodist Church and surrounding areas, 

with the estimated center line of the tornado damage path shown in red ....................... 176 

Figure 3–91.	 Estimated time–history of wind speed and direction near the Mass Hall of St. Paul’s
	

United Methodist Church................................................................................................ 177 

Figure 3–92.	 View from east of the damaged, MBS Mass Hall building of St. Paul’s United 

Methodist Church ........................................................................................................... 177 

Figure 3–93.	 Tapered rafter sections with bolted connection and roof purlins of St. Paul’s 

United Methodist Church................................................................................................ 178 

Figure 3–94.	 Damage to envelope of St. Paul’s United Methodist Church ......................................... 178 

Figure 3–95.	 Overview of damage at the Ramesh Shah Ophthalmology Center, with the 

estimated center line of the tornado damage path shown in red ..................................... 180 

Figure 3–96.	 Estimated time–history of wind speed and direction near the west side of the
 

Ramesh Shah Ophthalmology Center ............................................................................. 181 

Figure 3–97.	 Ramesh Shah Ophthalmology Center viewed from the southwest. ................................ 181 

Figure 3–98.	 Ramesh Shah Ophthalmology Center viewed from the east–southeast .......................... 182 

Figure 3–99.	 Close up view of the Ramesh Shah Ophthalmology Center showing connections 

and cable bracing of the steel frames .............................................................................. 182 

Figure 3–100. Close up view of the Ramesh Shah Ophthalmology Center showing connection 

between the steel frame with the concrete wall below.................................................... 183 

Figure 3–101. References for Joplin GIS database damage classifications and coding: light (green), 

medium (yellow), heavy/totaled (orange), and demolished (red) ................................... 186 

Figure 3–102. Overview of the Greenbriar Nursing Home, shown in relation to the estimated
 

center line of the tornado damage path (red line) ........................................................... 188 

Figure 3–103. Estimated time–history of wind speed and direction near the east side of the
 

Greenbriar Nursing Home............................................................................................... 189 

NIST NCSTAR 3, Joplin Tornado Investigation xxix 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

List of Figures 

Figure 3–104. Collapsed Greenbriar Nursing Home (viewed from the east) with missing roof system 

and collapsed exterior CMU walls. Note debris from building materials as well as 

other sources (automobiles) in all interior areas of the facility. ...................................... 189 

Figure 3–105. Collapsed Greenbriar Nursing Home.............................................................................. 190 

Figure 3–106. Collapsed Greenbriar Nursing Home (viewed from the north) showing the portion 

of the north wing’s exterior wall that did not collapse. .................................................. 190
 

Figure 3–107. Overview of the Mercy Village Apartments, shown in relation to the estimated center
 

line of the tornado damage path (red line). SJRMC is located to the west (left) of the 

apartments ....................................................................................................................... 192 

Figure 3–108. Estimated time–history of wind speed and direction near the northeast corner of the 

Mercy Village Apartments.............................................................................................. 193 

Figure 3–109. Hurricane tie–downs connecting wood roof trusses to load–bearing wood–frame 

Wall at the Mercy Village Apartments ........................................................................... 194 

Figure 3–110. L to R, pre–deflected wall hold–down, steel strap, and wall anchor at the Mercy
 

Village Apartments. ........................................................................................................ 195 

Figure 3–111. Mercy Village Apartments, viewed from the north, with envelope damage (sidings, 

window glazing, roof covering). ..................................................................................... 196 

Figure 3–112. Damage to the building envelope of the Mercy Village Apartments.............................. 196 

Figure 3–113. Residential failure due to disconnection of entire roof system (roof–to–wall
 

connection failure due to wind uplift)............................................................................. 199 

Figure 3–114. Failure of first–story–to–foundation wall connection. Entire roof and first floor
 

shifted off of lower story (directly north of SJRMC). .................................................... 200
 

Figure 3–115. Disconnection and loss of entire roof system. ................................................................ 201 

Figure 3–116. Typical roof–to–wall connection damage. ...................................................................... 201
 

Figure 3–117. Typical wall–to–foundation connections. ....................................................................... 202
 

Figure 3–118. Typical damage to residential dwelling envelope. .......................................................... 202 

Figure 3–119. Aerial photo showing the locations of the designated refuge area and TBO area in
 

the Walmart store, and a drawing containing the refuge area. ........................................ 205 

Figure 3–120. Location of the Training Room/designated refuge area at the Home Depot. Perimeter
 

tilt–up wall panels here collapsed inward and onto the safe area. .................................. 207 

Figure 3–121. North section of the Home Depot. Red line indicates perimeter tilt–up wall panels that
 

collapsed. Yellow line traces perimeter tilt–up wall panels (northeast corner, around 

loading dock) that did not collapse. Red rectangle designates the Training 

Room/designated refuge area. ......................................................................................... 208 

xxx NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

List of Figures 

Figure 3–122. View, from outside toward the west, of the Training Room/designated refuge area 

of the Home Depot.......................................................................................................... 209 

Figure 3–123. Locations of Tornado Safe Shelters (color blocks) in Joplin East Middle School
 

and their associated, pre–planned tornado evacuation routes (arrows of corresponding 

color). .............................................................................................................................. 211 

Figure 3–124. Locations of “storm shelters” at Joplin High School and pre–planned emergency
 

evacuation routes. ........................................................................................................... 212
 

Figure 3–125. Locations of areas of refuge (AOR, red blocks) on the first floor of the Ozark
 

Center building. .............................................................................................................. 214 

Figure 3–126. View of a typical hallway with damaged interior (ceiling, walls, and debris);
 

hallways were used as designated refuge areas in SJRMC’s East and West Towers. .... 216 

Figure 3–127. Typical floor plan of SJRMC’s East and West Towers (patient rooms along
	

perimeter and hallway toward the center)....................................................................... 216 

Figure 3–128. Wood–frame home completely destroyed except for the steel shelter bolted to the 

concrete floor in the garage............................................................................................. 220
 

Figure 3–129. Above–ground Kevlar® storm shelter bolted to concrete garage floor in residence that
 

was damaged during the Joplin tornado.......................................................................... 221 

Figure 3–130. Extent of damage (roof system disconnected) at residence with in–home, above–
	

ground Kevlar® storm shelter.......................................................................................... 221 

Figure 3–131. Destroyed EDE Power Substation 59. ............................................................................ 227 

Figure 3–132. High–pressure gas reducer valve at SJRMC that was damaged and leaked. .................. 229 

Figure 3–133. Liquid oxygen tank at SJRMC that leaked. .................................................................... 229 

Figure 4–1. Model #2001–130 Siren from the Federal Signal Company. ......................................... 244 

Figure 4–2. Siren locations for the City of Joplin. ............................................................................. 244 

Figure 4–3. The polygons associated with the 18 tornado warnings issued by the NWS between 

July 1, 2005, and May 25, 2011 (false alarms shown in red, warnings followed by 

verified tornadoes shown in blue)................................................................................... 249 

Figure 4–4. Locations of the 161 fatalities resulting from the Joplin tornado. Tornado estimated 

center track plotted in red. .............................................................................................. 254 

Figure 4–5. Joplin Elks Lodge #501 destroyed by the May 22, 2011, Joplin tornado. ...................... 257 

Figure 4–6. Damage to the interior of SJRMC. ................................................................................. 259 

NIST NCSTAR 3, Joplin Tornado Investigation xxxi 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

List of Figures 

Figure 4–7. The small brick wall in the foreground (to the left of the van) is one of the few portions 

of the Greenbriar Nursing Home left standing following the Joplin tornado. (The
 

building standing in the background was not part of the Greenbriar.)............................ 264 

Figure 4–8. Locations of places of worship, denoted by black plus signs (+) where people died
 

and yellow circles where there were no fatalities, along the tornado damage path 

(red line marks the estimated center track of the path) ................................................... 265 

Figure 4–9. The AT&T store following the Joplin tornado ............................................................... 268 

Figure 4–10.	 A view of the Home Depot building that collapsed in the Joplin tornado ...................... 271 

Figure 4–11.	 Damage to Dillon’s grocery inflicted by the Joplin tornado........................................... 274 

Figure 4–12.	 Aerial photo of the tornado–damaged Walmart Store #59, showing the collapsed
 

south half and uncollapsed north half of the building..................................................... 276 

Figure 4–13.	 Geographic locations of 104 of the 109 NIST interviewees who were located at home 

when the tornado hit Joplin. The red line indicates the estimated center track of the 

tornado ............................................................................................................................ 277 

Figure 4–14.	 Demolished home located within the tornado damage path in Joplin. ........................... 285 

Figure 4–15 The geographic locations of deaths in homes and apartments in Joplin. Detached 

homes are designated by pentagon shapes and apartments by square shapes, with 

the red line indicating the estimated center track of the tornado. ................................... 286
 

Figure 4–16.	 Geographic locations of NIST interviewees located outside of structures when the 

storm hit (13 individuals were in vehicles and 2 were outdoors). The red line represents 

the estimated center track of the tornado. Note: Two interviewees were located
 

slightly beyond the boundaries of the aerial photograph; their locations are shown
 

to scale ............................................................................................................................ 297 

Figure 4–17.	 The geographic locations of deaths that occurred in vehicles (indicated by the red and 

blue highway signs) and outdoors (black diamonds) when the storm hit. The red line 

is the estimated center track of the tornado. Note: Multiple deaths occurring at the 

same location are represented by only one symbol......................................................... 291 

Figure 4–18.	 Comparison, by age, of the 161 Joplin fatalities with U.S. tornado fatalities from
 

1996 through 2007 (Simmons and Sutter 2011) ............................................................. 296 

Figure 4–19.	 Comparison of fatality rates per thousand people within two populations: Population
 

1 – the entire population of Joplin and Population 2 – the population of the areas
 

within Joplin most affected by the tornado (U.S. Census Bureau 2010) ........................ 297 

Figure 4–20.	 Census tracts in Joplin that were affected by tornado damage. ...................................... 297 

Figure 4–21.	 Tornado–related injury rates by 10–year age range for residents of Jasper and 

Newton Counties (U.S. Census Bureau 2010) ................................................................ 298 

xxxii NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

List of Figures 

Figure 4–22. Geographic locations of the 154 fatalities (in red) and 35 severely injured persons (in 

blue) included in this analysis ......................................................................................... 302 

Figure 4–23. Geographic locations (labeled by name of structure or type of setting) of the 154 

fatalities and 35 severely injured persons included in the analysis of impact–related 

deaths and severe injuries ............................................................................................... 302 

Figure 4–24. The location of the five EF–Scale polygons overlaid on the aerial photo of the 

estimated tornado center track (red line) ........................................................................ 304 

Figure 4–25. Overhead view of tornado damage to Walmart Store #59 .............................................. 306 

Figure 4–26: A sample of the Picometry® database damage levels distinguished by color. ................ 308 

Figure 4–27. Aerial photo showing the AT&T store demolished by the storm (outlined in red) ........ 310
 

Figure 4–28. Tornado damage to the Joplin Elks Lodge...................................................................... 311 

Figure 4–29. Aerial photo showing damage to the Full Gospel Church building................................ 311
 

Figure 4–30. Aerial photo showing damage to Harmony Heights Baptist Church. ............................. 312 

Figure 4–31. Aerial photo showing damage to the Joplin Pizza Hut ................................................... 312 

Figure 4–32. Aerial photo showing damage to the Stained Glass Theater. ......................................... 313 

Figure 4–33. Aerial photo showing damage to the Meadows Healthcare facility (outlined in red)..... 314 

Figure 4–34. Aerial photo showing damage to Walmart Store #59, including the red box (circled
 

in white) to indicate the store’s refuge area .................................................................... 315 

Figure 4–35. Aerial photo showing damage to the Home Depot (outlined in red). ............................. 316 

Figure 4–36. Damage to the interior of SJRMC. ................................................................................. 317 

Figure 4–37. Aerial photo showing damage to two apartment complexes in Joplin at 2001 

Connecticut Avenue (outlined by solid red line) and 2034 Connecticut Avenue (within 

dotted line) ...................................................................................................................... 321 

Figure 4–38. Aerial photo showing damage to the Hampshire Terrace apartments. ........................... 322 

Figure 4–39. Aerial photo showing damage to the Greenbriar Nursing Home. ................................... 323 

Figure 4–40. Graphic showing the location of all 154 impact–related fatalities in relation to the EF
 

wind speed zones (red = EF–4, orange = EF–3, yellow = EF–2, green = EF–1, and 

blue = EF–0). .................................................................................................................. 326 

Figure 4–41. A model depicting protective–action decision–making in the May 22, 2011 Joplin
 

tornado ............................................................................................................................ 328 

NIST NCSTAR 3, Joplin Tornado Investigation xxxiii 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

List of Figures 

Figure 4–42. Tornado fatality rates per thousand people within two populations: Population 1 – the 

entire population of Joplin and Population 2 – the population of the areas within 

Joplin most affected by the tornado (154 impact–related deaths)................................... 331 

Figure 4–43. Tornado fatality rates (154 impact–related fatalities) and Residential tornado fatality
 

rates (single–family homes and apartments, only).......................................................... 332 

Figure D–1. Main (top) and interaction (bottom) effects plots for input and output parameters ........ 380 

Figure D–2. Histograms showing values of DW and DR for X = 2.1 miles...................................... 382 

Figure D–3. Area and grid point for detailed factorial design ............................................................ 383 

Figure D–4. Interaction effects plots for DW (top) and DR (bottom) for X = 2.1 miles. ................... 384 

Figure D–5. Interaction effects plots for β = 90 degrees (top) and β = 180 degrees (bottom) for
 

X = 2.1 miles................................................................................................................... 385 

Figure E–1. Estimated time–history of wind speed and direction near the center of Walmart .......... 387
 

Figure E–2. Estimated time–history of wind speed and direction near the center of Franklin 

Technology Center .......................................................................................................... 388 

Figure E–3. Estimated time–history of wind speed and direction near the center of Home Depot .... 389 

Figure E–4. Estimated time–history of wind speed and direction slightly east of the center of St. 

John’s Regional Medical Center (near the south end of the East Tower) ....................... 390
 

Figure E–5. Estimated time–history of wind speed and direction near the center of Joplin East
 

Middle School ................................................................................................................. 391 

Figure E–6. Estimated time–history of wind speed and direction near the center of Joplin High 

School ............................................................................................................................. 392 

Figure F–1. Map of EF–0 tornadoes per year..................................................................................... 393 

Figure F–2. Map of EF–1 tornadoes per year..................................................................................... 394 

Figure F–3. Map of EF–2 tornadoes per year..................................................................................... 394 

Figure F–4. Map of EF–3 tornadoes per year..................................................................................... 395 

Figure F–5. Map of EF–4 tornadoes per year..................................................................................... 395 

Figure F–6. Map of EF–5 tornadoes per year..................................................................................... 396 

Figure H–1. Wind pressure distribution for the Walmart building ..................................................... 404 

Figure I–1. Wind pressure distribution for MWFRS of the Home Depot building ........................... 406 

Figure J–1. Wind pressure distribution along length of the Joplin East Middle School
 

Gymnasium ..................................................................................................................... 414 

Figure J–2. Wind pressure distribution on the cross section of the Joplin East Middle School
 

Gymnasium ..................................................................................................................... 414 

xxxiv NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

LIST OF TABLES
	

Table E–1. Summary of NIST recommendations ............................................................................... lvi
 

Table 2–1. Enhanced Fujita Scale....................................................................................................... 35 

Table 2–2. Estimated wind speeds for NIST–surveyed structures using EF Scale............................. 37 

Table 2–3. Wind speed statistics and numbers of structures estimated for residential damage levels 

using EF Scale .................................................................................................................. 38 

Table 2–4. Observed Joplin tree fall metrics. ..................................................................................... 46 

Table 2–5. Estimated areas affected by wind speeds falling within the EF wind–speed ranges, within 

Joplin grid system and in theoretical EF–4 and EF–5 tornadoes. ..................................... 52 

Table 2–6. NIST best estimate of maximum wind speeds for NIST–surveyed structures using
 

tornado wind field model and EF Scale. ........................................................................... 55 

Table 2–7. Percentage of tornado–affected areas exhibiting EF–3 or greater damage, given damage 

occurs and given specified tornado rating......................................................................... 60 

Table 2–8. Sample of significant tornado events in Joplin region ...................................................... 66 

Table 3–1. Summary of building–related losses from the Joplin tornado .......................................... 78 

Table 3–2. List of NIST–surveyed buildings with damage condition and design information .......... 81 

Table 3–3. Summary of significant changes in codes and standards pertaining to wind design ........ 87 

Table 3–4. History of code adoptions and amendments relevant to wind design by the City of
 

Joplin, Missouri ................................................................................................................ 90
 

Table 3–5. Distribution of tornado–affected residential structures by level of damage sustained and 

year built ......................................................................................................................... 185 

Table 3–6. Correlation between degree of damage and age of residential construction, by severity of
 

wind speed ...................................................................................................................... 198 

Table 3–7. Timeline of Electrical Power Restoration. ...................................................................... 225 

Table 4–1. Distribution of fatalities based upon location of injury/death from the Joplin tornado 

listed in alphabetical order by location name.................................................................. 253 

Table 4–2. Distribution of injured persons based upon where injury was sustained, using CDC EpiAid Study data ................................................................................................................ 255 

NIST NCSTAR 3, Joplin Tornado Investigation xxxv 
 

 

List of Tables 

Table 4–3. Number of impact–related fatalities by location (of death or injury that led to death)
 

resulting from the Joplin tornado. ................................................................................... 300
 

Table 4–4. Distribution of 35 severely injured persons (from the CDC sample) based upon the
 

locations where they were injured in the Joplin tornado. ............................................... 301 

Table 4–5. Wind speeds associated with fatalities and severe injuries among people located outside 

of buildings ..................................................................................................................... 305 

Table 4–6. Details on the wind environment, building type, building damage, and actions taken by
 

the deceased for seven buildings in which people died in the Joplin tornado ................ 309 

Table 4–7. Details on the fatalities, wind environment, building type, building damage, and actions 

taken by the deceased for residential buildings impacted by the Joplin tornado ............ 319 

Table 4–8. Wind speeds associated with impact–related fatalities and severe injuries – all
 

locations .......................................................................................................................... 324 

Table 4–9. Impact–related fatalities and severe injuries by distance from the tornado estimated center
 

track. ............................................................................................................................... 324 

Table D–1. Final input parameter ranges........................................................................................... 381 

Table G–1. City of Joplin Code Adoptions ....................................................................................... 397 

Table H–1. Net internal pressure and internal suction for the Walmart building. ............................. 403 

Table I–1. Net internal pressure and internal suction for MWFRS of the Home Depot building. ... 406 

Table J–1. Wind pressure acting on the MWFRS of the Joplin East Middle School gymnasium ... 413 

Table K–1. The number of qualifying community emergency management websites chosen, by
 

State. ............................................................................................................................... 416 

xxxvi NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LIST OF ACRONYMS AND ABBREVIATIONS
	

Acronyms 

ACI American Concrete Institute 

AHJ authority having jurisdiction 

AISC American Institute of Steel Construction 

ANS American Nuclear Society 

ANSI American National Standards Institute 

ASCE American Society of Civil Engineers 

ASOS automated surface observing system 

ATC Applied Technology Council 

AWS American Welding Society 

BOCA Building Officials and Code Administrators 

BOMA Building Owners and Managers Association International 

BTS box–type system 

CAPE convective available potential energy 

CDC U.S. Centers for Disease Control and Prevention 

CIP cast–in–place 

CMAS Commercial Mobile Alert System 

CMU concrete masonry unit 

COV coefficient of variation 

DHS U.S. Department of Homeland Security 

DHS IP DHS Office of Infrastructure Protection 

DHS S&T DHS Science and Technology Directorate 

DI damage indicator 

DOD degree of damage 

DOE U.S. Department of Energy 

DR damage ratio 

DW damage width 

EAS Emergency Alert System 

EDE Empire District Electric 

NIST NCSTAR 3, Joplin Tornado Investigation xxxvii 
 

 

 

 

List of Acronyms and Abbreviations 

EF Scale Enhanced Fujita Scale 

EM emergency manager 

EOC emergency operations center 

EPDM ethylene propylene diene monomer 

FCC Federal Communications Commission 

FEMA Federal Emergency Management Agency 

F Scale Fujita Scale 

FY fiscal year 

GIS geographic information system 

IAFC International Association of Fire Chiefs 

IAEM International Association of Emergency Managers 

IBC International Building Code 

ICC International Code Council 

ICU intensive care unit 

IEC International Electrotechnical Commission 

IFMA International Facility Managers Association 

IRC International Residential Code 

ISO International Organization for Standardization 

MAW Missouri American Water Company 

MBS metal building systems 

MCD Mesoscale Convective Discussion 

MDHSS Missouri Department of Health and Senior Services 

MGE Missouri Gas Energy 

MOB medical office building 

MRH mean roof height 

MRI mean recurrence interval 

MSSU Missouri Southern State University 

MWFRS main wind–force resisting system 

NAC National Association of Counties 

NAHB National Association of Home Builders 

NBC National Building Code 

NCST National Construction Safety Team 

xxxviii NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

List of Acronyms and Abbreviations 

NCSL National Conference of State Legislators 

NEMA National Emergency Management Association 

NFPA National Fire Protection Association 

NIST National Institute of Standards and Technology 

NOAA National Oceanic and Atmospheric Administration 

NRC U.S. Nuclear Regulatory Commission 

NSF National Science Foundation 

NWR NOAA weather radio 

NWS National Weather Service 

OFCM Office of the Federal Coordinator for Meteorological Services and Supporting Research 

PCA Portland Cement Association 

PCI Precast/Prestressed Concrete Institute 

PE physical education 

PSDA post–storm data acquisition 

QRT quick response team 

RC reinforced concrete 

RG Regulatory Guide 

RMW radius of maximum wind 

SAVE Structural Assessment and Visual Evaluation 

SDI Steel Deck Institute 

SEAKM Structural Engineers Association of Kansas and Missouri 

SF steel frame 

SJI Steel Joist Institute 

SJRMC St. John’s Regional Medical Center

SPC Storm Prediction Center 

SPRI Single Ply Roofing Industry 

TBO tire and battery operation 

TMS The Masonry Society 

TO.W tornado warning 

UL Underwriters Laboratories 

URM unreinforced masonry 

UTC Coordinated Universal Time 

NIST NCSTAR 3, Joplin Tornado Investigation xxxix 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

List of Acronyms and Abbreviations 

WFO weather forecast office 

Abbreviations 

ft foot 

ft2 square foot 

in. inch 

J/kg joules per kilogram 

kg kilogram 

kip a force equal to 1,000 pounds 

km kilometer 

km2 square kilometer 

lb pound 

lb/ft2 pounds per square foot 

m meter 

mb millibar 

min minute 

mph miles per hour 

m/s meters per second 

Pa pascal 

plf pounds per linear foot 

psf pounds per square foot 

s second 

xl NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

METRIC CONVERSION TABLE
	

To convert from to Multiply by 

AREA AND SECOND MOMENT OF AREA 

square foot (ft2) square meter (m2) 9.290 304 E–02 

square inch (in.2

) square meter (m2) 6.4516 E–04 

FORCE 

kilogram–force (kgf) newton (N) 9.806 65 E+00 

kilopond (kilogram–force) (kp) newton (N) 9.806 65 E+00 

kip (1 kip=1,000 lbf) newton (N) 4.448 222 E+03 

kip (1 kip=1,000 lbf) kilonewton (kN) 4.448 222 E+00 

pound–force (lbf) newton (N) 4.448 222 E+00 

FORCE DIVIDED BY LENGTH 

pound–force per foot (lbf/ft) newton per meter (N/m) 1.459 390 E+01 

pound–force per inch (lbf/in.) newton per meter (N/m) 1.751 268 E+02 

LENGTH 

foot (ft) meter (m) 3.048 E–01 

inch (in) meter (m) 2.54 E–02 

MASS and MOMENT OF INERTIA 

kilogram–force second squared 

per meter (kgf  s 

2

/m) kilogram (kg) 9.806 65 E+00 

pound foot squared (lb  ft2

) kilogram meter squared (kg  m 2) 4.214 011 E–02 

pound inch squared (lb  in.

2

) kilogram meter squared (kg  m 2) 2.926 397 E–04 

NIST NCSTAR 3, Joplin Tornado Investigation xli 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Metric Conversion Table 

To convert from to Multiply by 

PRESSURE or STRESS (FORCE DIVIDED BY AREA) 

kilogram–force per square centimeter (kgf/cm2) pascal (Pa) 9.806 65 E+04 

kilogram–force per square meter (kgf/m2) pascal (Pa) 9.806 65 E+00 

kilogram–force per square millimeter (kgf/mm2

) pascal (Pa) 9.806 65 E+06 

kip per square inch (ksi) (kip/in.2

) pascal (Pa) 6.894 757 E+06 

kip per square inch (ksi) (kip/in.2

) kilopascal (kPa) 6.894 757 E+03 

millibar (mb) pascal (Pa) 1.0 E+02 

pound–force per square foot (lbf/ft2

) pascal (Pa) 4.788 026 E+01 

pound–force per square inch (psi) (lbf/in.2

) pascal (Pa) 6.894 757 E+03 

pound–force per square inch (psi) (lbf/in.2) kilopascal (kPa) 6.894 757 E+00 

psi (pound–force per square inch) (lbf/in.2

) pascal (Pa) 6.894 757 E+03 

psi (pound–force per square inch) (lbf/in.2

) kilopascal (kPa) 6.894 757 E+00 

VELOCITY (includes SPEED) 

foot per second (ft/s) meter per second (m/s) 3.048 E–01 

kilometer per hour (km/h) meter per second (m/s) 2.777 778 E–01 

mile per hour (mi/h) kilometer per hour (km/h) 1.609 344 E+00 

mile per minute (mi/min) meter per second (m/s) 2.682 24 E+01 

xlii NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

EXECUTIVE SUMMARY
	

E.1 INTRODUCTION
 

Tornadoes typically affect much smaller geographic areas compared with other natural hazards like 

earthquakes and hurricanes, but occur at a much higher frequency and cause more deaths than those two 

hazards combined. The May 22, 2011, Joplin tornado, rated EF–5 on the Enhanced Fujita tornado 

intensity scale, was one of the estimated 1,691 tornadoes that occurred in the United States in 2011.1 

During the period from 1950 (the beginning of official tornado record keeping) through 2011, U.S. 

tornadoes caused about 5,600 fatalities.2 This number well exceeds the toll for U.S. hurricanes and 

earthquakes over the same period (3,1021 and 459,3 respectively). 

The Joplin tornado caused 161 fatalities and more than 1,000 injuries, making it the deadliest single 

tornado on record since the official U.S. records began in 1950.1 It was a record tornado that occurred in 

a year of record U.S. tornado activity and impacts. To put the Joplin tornado’s death toll into perspective, 

the 161 fatalities that resulted from it (out of the total of 553 U.S. tornado deaths in 2011) were almost 

twice the national average of 91.6 tornado fatalities per year (since 1950), more than three times the 

average of 50.8 hurricane deaths per year, and more than twenty times the average of 7.5 earthquake 

fatalities per year. The Joplin tornado’s high death toll occurred despite an official tornado warning time 

of about 17 minutes4

, greater than the National Weather Service (NWS) national average warning time of 

approximately 14 minutes.5 

The Joplin tornado also was a record–setter in terms of damage to the built environment and economic 

loss. It was on the ground for about 22 miles (6 miles within the City of Joplin over the span of 13 

minutes), long enough to severely damage well–developed commercial and residential areas in Joplin that 

were home to about 41 percent of the city’s population (20,820 people, out of the 50,175 estimated to 

reside in Joplin in 20106

). The resulting damage to the built environment (not counting losses due to 

business disruption) was the costliest on record for a tornado, with insured losses initially estimated to be 

as high as $3 billion.7 Nearly a year after the storm, the City of Joplin, quoting data provided by the 

Missouri Department of Insurance, Financial Institutions, and Professional Registration, reported that 

insured commercial property losses had reached $1.228 billion and residential property losses were at 

$0.552 billion.8 

1 NOAA (www.noaanews.noaa.gov/2011_tornado_information.html). 

2 NWS (www.nws.noaa.gov/om/hazstats/resources/weather_fatalities.pdf). 3 Deaths from U.S. Earthquakes (http://earthquake.usgs.gov/earthquakes/states/us_deaths.php). 4 The first set of sirens were initiated 23 minutes before official touchdown; however, this siren initiation was based upon a different 

storm to the north of Joplin that never produced a tornado. 

5 NWS average for 2008 (www.nws.noaa.gov/cfo/program_planning/doc/FY2009%20NOAA's%20NWS%20National%20Performance%20Measures%20-%20Graph%20Update.pdf). 6 United States Census Bureau (www.census.gov/newsroom/emergencies/2011_tornadoes.html). 7 According to a preliminary loss estimate issued by EQECAT (www.eqecat.com/catWatchREV/secureSite/report.cfm?id=321). 8 City of Joplin (www.joplintornadoanniversary.com/resources/city-of-joplin-factsheet5-14-12.pdf). 

NIST NCSTAR 3, Joplin Tornado Investigation xliii 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Executive Summary 

The majority of the Joplin tornado fatalities (83.8 percent, or 135 of the 161 deaths) occurred inside 

buildings. In all, about 553 non–residential buildings, comprising types of structures commonly found in 

U.S. cities, were severely damaged in the Joplin tornado, including 1 of the 2 major hospitals serving the 

City of Joplin, 10 of the 20 local public schools, several parochial schools, 28 churches, 2 fire stations, 

and both large and small commercial facilities. The storm also damaged nearly 7,500 residential 

structures, from single–family homes to large apartment buildings.9 The high death toll occurred in 

buildings of varying types, despite a relatively generous warning time in a city with a long history of 

adopting the latest model building codes. This brings into question the effectiveness of current U.S. 

tornado warning systems and practices, and whether building safety in tornadoes can be enhanced, given 

that current national building standards, codes, and practices do not require buildings to be built to 

withstand tornadoes or to include tornado shelters or safe rooms.10 

Disasters such as the Joplin tornado provide unfortunate but important opportunities to learn from the 

performance of structures, emergency communications, and human behavior during catastrophic events. 

Insight gained from such learning can lead to improvements in standards, codes, and practices that will 

reduce losses and improve safety in future events. This report documents the findings and 

recommendations resulting from the technical investigation of the May 22, 2011, Joplin tornado 

undertaken by the U.S. Commerce Department’s National Institute of Standards and Technology

(NIST).11 

E.2 NIST RESPONSE AND SCOPE OF THE TECHNICAL INVESTIGATION 

NIST began assessing the Joplin tornado and its associated impacts in the immediate aftermath of the 

disaster. Based on initial information about the human toll of the storm and its impact on buildings and 

other structures, NIST deployed a four–person reconnaissance team to collect perishable data and to make 

a recommendation about whether a more detailed study was warranted. This team, which included NIST 

researchers with expertise in structural and fire engineering, extreme wind, and sociology, deployed to 

Missouri on May 24, 2011, two days after the tornado struck, and conducted field reconnaissance in 

Joplin May 25–28, 2011.12 

The NIST reconnaissance team determined, based on its analysis of the data collected during the 

reconnaissance, that this event provided a significant opportunity to learn from what happened and to 

improve safety in the future. On June 29, 2011, NIST Director Patrick Gallagher—by implementing 

legislative authority provided in the National Construction Safety Team Act (NCST)13 —established a 

NCST Team to conduct a detailed technical investigation of the May 22, 2011, Joplin tornado. The 

establishment of the NCST Team was announced in the Federal Register on July 19, 2011 (76 FR 42683). 

9 Joplin Area Chamber of Commerce (http://www.regionalpartnership.contros.com/JACC%20Fact%20Sheet%205-1-12.pdf). 10 The City of Joplin, like most other municipalities in tornado high-hazard areas and like the contemporaneous model building 

codes, did not mandate the construction of shelters or safe rooms in residential or commercial facilities at the time of the May 22, 

2011, Joplin tornado. 11 NIST is a non-regulatory agency of the Department of Commerce. 12 See www.nist.gov/el/disasterstudies/upload/Joplin_Reconnaissance_Presentation061511-2.pdf for more information about 

NIST’s preliminary reconnaissance in Joplin. 13 Public Law 107-231, October 1, 2002, 116 Stat. 1471 (15 U.S.C. 7301 et seg.). information about the NCST is available at
 

www.nist.gov/el/disasterstudies/ncst/aboutncst.cfm.
 

xliv NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

Executive Summary 

The NCST Team consisted of four researchers from NIST’s Engineering Laboratory14 with expertise in 

structural and fire engineering, extreme wind, and sociology (human behavior and emergency response). 

In addition to the NIST researchers, a researcher with expertise in meteorology and severe storms and 

warnings from the National Oceanic and Atmospheric Administration’s National Severe Storms 

Laboratory was also named as part of the NCST Team. 

The scope of the investigation of the Joplin tornado included analyses of the wind environment and 

technical conditions that may have contributed to the fatalities and injuries, the performance of 

emergency communications systems, the public’s response to emergency communications, and the 

performance of buildings and lifelines. The primary outcomes (findings and recommendations) of the 

NIST technical investigation provide a technical basis for improved codes, standards, and practices 

related to tornado hazard characterization, tornado–resilient design and construction, emergency 

communications systems, and emergency response. It is anticipated that the findings and 

recommendations in this report will contribute to the voluntary consensus process that is used to develop 

U.S. codes, standards, and practices. 

The goals of the NCST technical investigation of the May 22, 2011, Joplin tornado were: 

	 To investigate the wind environment and technical conditions associated with fatalities and 

injuries, the performance of emergency communications systems and the public response to 

such communications, and the performance of residential, commercial, and critical buildings, 

designated safe areas in buildings, and lifelines. 

	 To develop findings and recommendations that can serve as the basis for 

	 Potential improvements to requirements for design and construction of buildings, 

designated safe areas, and lifeline facilities in tornado–prone regions; 

	 Potential improvements to guidance for tornado warning systems and emergency 

response procedures; 

	 Potential revisions to building, fire, and emergency communications codes, standards, 

and practices; and 

	 Potential improvements to public safety. 

To achieve those goals, five specific NCST technical investigation objectives were identified: 

1.	 Determine the tornado hazard characteristics and associated wind fields in the context of 

historical data 

2.	 Determine the response of residential, commercial, and critical buildings, including the 

performance of designated safe areas 

NIST’s Engineering Laboratory supports U.S. industry and public safety by providing critical tools—metrics, models, and 

knowledge—and the technical basis for standards, codes, and practices. 

NIST NCSTAR 3, Joplin Tornado Investigation xlv 

14 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Executive Summary 

3.	 Determine the performance of lifelines15 as it relates to the continuity of operations of 

residential, commercial, and critical buildings 

4.	 Determine the pattern, location, and cause of fatalities and injuries, and associated emergency 

communications and public response 

5.	 Identify, as specifically as possible, areas in current building, fire, and emergency 

communications codes, standards, and practices that warrant revision 

E.3 THE HAZARD CONTEXT 

In the days leading up to the May 22, 2011, Joplin tornado, forecasters at the National Weather Service 

(NWS) Storm Prediction Center (SPC) were becoming more certain about the impending occurrence of a 

significant weather event; one that would include thunderstorms and possible tornadoes, in a region that 

encompassed Joplin, Missouri. Given their location in “tornado alley,” residents in the vicinity of Joplin 

were no strangers to tornadic activity. According to the SPC, from 1950 through 2011, the area within an 

80–mile radius of Joplin encountered a total of 766 tornadoes (of which 6 percent were rated EF–3 or 

higher), or an average of 12.5 tornadoes per year. A total of 182 tornadoes rated EF–2 or greater struck 

the region during this period. 

On Sunday, May 22, 2011, forecaster confidence in a severe weather event grew, and the SPC issued a 

tornado watch for Joplin and surrounding communities at 3:00 p.m. Although conditions required for 

thunderstorms were present in the region, the conditions in Joplin were relatively quiescent at this time. 

At 4:33 p.m., NWS forecasters in Springfield, Missouri, briefed the Joplin–Jasper County Emergency 

Manager (EM) on severe storms to the west (NWS 2011). At 5:09 p.m., a tornado warning was issued for 

a storm cell affecting the northeast part of Joplin. At 5:11 p.m., the Joplin–Jasper County EM sounded 

the tornado sirens throughout Joplin. The decision to sound the siren system was made by the Joplin–

Jasper County EM based on conversations between emergency management personnel in Cherokee 

County, Kansas (immediately west of Jasper County) and Joplin–Jasper County, information received 

from the NWS about the impending (5:09 p.m.) warning affecting northeast Joplin, the direction of travel 

of the storm that was the subject of the 5:09 warning, and anecdotal information from a local emergency 

official (outside of Joplin) regarding the destruction associated with that storm. This sounding caused 

some confusion among Joplin residents, since at this time there were few environmental clues to suggest 

that severe weather was imminent. 

At 5:17 p.m., the NWS office in Springfield, Missouri, issued another tornado warning for a different 

storm which included southwest Jasper County and encompassed the entire city of Joplin. At 5:34 p.m., 

an emergency response official located in the area reported seeing a tornado touching down southwest of 

the Joplin city limits, and 4 minutes later, a police officer spotted the tornado entering the city. About this 

time, the tornado sirens were sounded for a second time in the Joplin area. The tornado followed a six–

mile, roughly west–to–east path through Joplin, and was up to a mile wide in some places. At 5:48 p.m., 

the NWS issued a third tornado warning to extend the warning area to the east of Joplin. By 5:50 p.m., 

15 Lifelines considered in this investigation were electrical power, natural gas, and water supply infrastructure and facilities. 

xlvi NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Executive Summary 

the tornado was moving out of Joplin after exacting a terrible toll in the city. The overall length of the 

tornado’s path was 22.1 miles.

E.4 PRINCIPAL FINDINGS 

NIST developed findings based upon information collected during and after the initial reconnaissance, 

interviews conducted with survivors, and data analyses related to environmental conditions, building 

performance, and emergency response and communications activities. These findings are enumerated in 

Sec. E.4.2, following the contextual observations presented in Sec. E.4.1. 

E.4.1 Context for Findings 

	 National model building codes, standards, and practices seek to achieve life safety for the 

hazards that are considered in design. While these considerations include hurricane and 

nontornadic wind, flood, snow, rain, earthquake, and ice loads, they do not include tornado 

hazards (loads due to wind speeds that significantly exceed code–compliant design wind 

speed and impacts of wind–borne debris). Thus, buildings and other structures are not 

designed for tornado hazards currently. The sole exceptions are safety–related structures in 

nuclear power plants and storm shelters or safe rooms. 

	 There are currently two tornado hazard maps prescribing different tornado hazard 

regionalization and associated wind speeds for the contiguous United States: 

	 The ANSI/ANS 2.3 (2011), NRC/RG 1.76 (2007), and DOE 1020 (2002) map for 

designing nuclear–related facilities (three regions, 230 mph maximum wind speed); and 

	 The ICC 500 (2008), FEMA 320 (2008), and FEMA 361 (2008) map for designing 

shelters and safe rooms (four regions, 250 mph maximum wind speed). 

	 Current building codes and standards prohibit the use of aggregate roof surfacing materials or 

ballast for hurricane–prone regions,16 but allow their use in other regions based on mean roof 

height and exposure category. For the City of Joplin, the building code17 at the time of the 

May 22, 2011 Joplin tornado allowed aggregate roof ballast for buildings with a mean roof 

height of less than 110 ft. 

	 In the State of Missouri, the adoption and enforcement of building codes are prerogatives of 

local government. The City of Joplin’s building department has a long history of code

adoptions, and typically has adopted the latest national model building codes shortly after 

they have been issued. 

16	 Defined in ASCE/SEI Standard 7–10 Minimum Design Loads for Buildings and Other Structures as: Areas vulnerable to 

hurricanes; in the United States and its territories defined as (1) The U.S. Atlantic Ocean and Gulf of Mexico coasts where the 

basic wind speed for Risk Category II buildings is greater than 115 mph, and (2) Hawaii, Puerto Rico, Guam, Virgin Islands, and 

American Samoa. 

17 IBC 2006 

NIST NCSTAR 3, Joplin Tornado Investigation xlvii 
 

 

 

 

 

 

 

 

 

 

Executive Summary 

	 Like most other municipalities in tornado–prone areas and the contemporaneous model 

building codes, the City of Joplin does not mandate the construction of shelters or safe rooms 

in residential or non–residential facilities. Additionally, the City did not own or operate any 

public storm shelters. The lack of public shelters and requirements for safe rooms in 

residential or non–residential facilities meant that many residents in the area affected by the 

May 22, 2011, Joplin tornado, particularly those who were living in multi–family residential 

buildings or older nursing homes, did not have access to such sheltering options during this 

tornado. 

E.4.2 Findings of the Technical Investigation 

NIST’s findings are grouped by objective as listed below. To aid in identifying individual findings, the 

findings are numbered consecutively. In addition, several of the findings in the May 22, 2011, Joplin 

tornado that pertain to building performance (specifically findings 8, 9, 10, and 17 of Objective 2) listed 

below are consistent with observations regarding responses of critical and educational facilities during the 

May 20, 2013, tornado in Moore, Oklahoma (NIST 2013). 

Objective 1. Determine the tornado hazard characteristics and associated wind fields in the context 

of historical data 

	 Measurements of the Near–Surface Wind Field in Tornadoes 

Finding 1:	 Current operational weather radar technology is incapable of determining tornado 

occurrence and intensity at heights above the ground that are relevant to structural 

engineering design (i.e. at the heights of buildings). For example, because the nearest 

operational radars to Joplin were more than 60 miles away they could only measure 

conditions at altitudes starting at 5000 ft. 

Finding 2:	 Reliable direct measurement of wind speed in tornadoes, especially the most intense 

tornadoes, is lacking or non–existent. Wind speed measurements related, but not 

directly, to the May 22, 2011, Joplin tornado were limited to one location well outside 

the tornado damage path. The difficulty in measuring tornado intensity discussed in 

both Findings 1 and 2 have been noted in previous tornado research. 

Finding 3:	 NIST estimated the maximum wind speeds in the May 22, 2011, Joplin tornado to be 

175 mph with up to 25 percent of uncertainty. With uncertainty, the upper bound of the 

estimated maximum wind speed in the Joplin tornado was 210 mph. The uncertainty 

was due to the use of indirect wind speed estimation methods (i.e., tree–fall analysis, 

EF Scale). Due to the lack of radar and direct wind speed measurements, indirect 

methods served as the sole estimators of wind speeds in the May 22, 2011, Joplin 

tornado. While existing indirect methods cannot be used to unambiguously determine 

wind speeds that can be used in structural design, the remaining findings in this study 

are not sensitive to the level of uncertainty in this methodology. 

Finding 4:	 The estimated duration and spatial extent of damaging winds in the May 22, 2011, 

Joplin tornado were significantly greater than those expected based on those used in 

current tornado hazard models. This finding is consistent with other studies that have 

estimated wind fields in actual tornadoes. For example, wind speeds in the Joplin 

xlviii NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

Executive Summary 

tornado that exceeded those associated with EF–3 accounted for approximately twice 

the spatial area expected based on modeled estimations for an EF–5 tornado. 

 Assessment of Tornado Climatology, Hazard, and Risk for Structural Design 

Finding 5:	 The probability of occurrence and subsequent risk of tornadoes is significantly 

underestimated by point–based methodology. It was shown that actual damage in 

Joplin and other communities affected by damaging tornadoes was greater than 

predicted using point–based methodology. 

Finding 6:	 Tornadoes rated EF–3 or lower have accounted for approximately 96 percent of all 

U.S. tornadoes between 1950 and 2011, over one–third (36 percent) of the 

approximately 5,600 tornado–related fatalities over the same period, and about 80 

percent of the $25 billion18 in estimated property losses incurred due to tornadoes 

between 1996 and 2011. Even in a tornado with intensity greater than EF–3, the wind 

speeds in the majority of the affected area are equivalent to or less than the maximum 

wind speeds associated with EF–3 tornadoes. In the case of the Joplin tornado, 

approximately 40 percent of the fatalities and as much as 90 percent of the tornado area 

were associated with EF–3 or lower wind speeds. 

 Limitations of the Enhanced Fujita (EF) Scale 

Finding 7:	 The Enhanced Fujita scale lacks adequate damage indicators (DI’s) and corresponding 

degrees of damage (DOD’s) for distinguishing among the most intense tornado events. 

The lack of DI’s and DOD’s and overall nature of the EF–scale requires subjective, 

non–quantitative assessment of tornado damage. 

Objective 2. Determine the response of residential, commercial, and critical buildings, 

including the performance of designated safe areas
 

 Building Performance 

Finding 8:	 Buildings are not designed to withstand tornado hazards and there are no building code 

requirements for tornado–resistant design. Most buildings in the area damaged by the 

May 22, 2011, Joplin tornado were subjected to wind speeds close to or above the 

speeds that would be expected to cause collapse of or major damage to structures 

designed to the non–tornadic wind design requirements of the building codes 

applicable to them. Wind–borne debris, which contributed significantly to building 

damage in Joplin, also is not considered as a hazard in building design. 

Finding 9:	 Regardless of construction type, neither affected residential nor non–residential 

buildings were able to provide life–safety protection in the May 22, 2011, Joplin 

tornado. Of the 161 fatalities, 135 (or 83.8 percent) were related to building failure. Of 

these building failure–related fatalities, 74 (52.5 percent) occurred in residential 

buildings. Of the buildings that were damaged, 7,411 were residential and 553 were 

non–residential. All 553 of the non–residential buildings and 3,069 (about 43 percent) 

of the residential structures sustained either heavy/totaled or demolished damage 

In 2011 dollars. 

NIST NCSTAR 3, Joplin Tornado Investigation xlix 

18 
 

 

 

 

 

 

 

 

Executive Summary 

classification, resulting in $1.228 billion in reported insured losses for non–residential 

property and $0.552 billion for residential property. 

Finding 10:	 Among the engineered buildings surveyed by NIST, those with redundant lateral load 

capacity and those that did not depend on bracing from the roof system for lateral 

stability (such as certain steel and concrete moment frame buildings) withstood the 

tornado without structural collapse. Those with reinforced concrete roofs or composite 

concrete and steel roofs also withstood the tornado without structural collapse. Those 

that relied on bracing from a less robust roof system for lateral stability (such as box–

type system (BTS) buildings with light steel roof decks) were prone to structural 

collapse. 

Finding 11: The structural collapses of NIST–surveyed BTS buildings began with failure of the roof 

system due to wind uplift (failure of roof–deck–to–joist or joist–to–wall connections), 

which led to the loss of lateral bracing for perimeter walls, causing them to collapse by 

rotation at the base due to lateral load. Available design information showed that the 

roof connections of these buildings were adequate for code–level design wind 

pressures, making it unlikely that these buildings could have failed in wind speeds 

under 115–120 mph, which are the “ultimate” (that is, sufficient for failure) speeds 

corresponding to the code–level winds. 

Finding 12:	 BTS buildings, surveyed by NIST, that sustained total structural collapse had two 

common design features that increased their vulnerability to collapse in the May 22, 

2011, Joplin tornado: light–gauge metal roof systems, and friction–only wall–to–

footing connections (currently accepted practice for areas with low or no seismic risk). 

Finding 13:	 Metal building systems (MBS) surveyed by NIST sustained significant damage to their 

envelopes, but no structural collapses of the primary rigid steel frame. 

Finding 14:	 Failures of residential wood–frame buildings predominantly involved failure of the 

connections between structural components, rather than of the components themselves 

(roof, walls, and floor), with the majority involving disconnection of the roof from 

walls and walls from foundation. This indicates lack of robustness in the connections 

and in the continuity of the vertical load path from roof to foundation. 

Finding 15:	 Better structural performance in one of the NIST–surveyed multi–family residential 

buildings in Joplin can be attributed to use of robust hurricane connectors, typically 

only required for residential wood–frame buildings in hurricane–prone regions. 

Finding 16:	 All NIST–surveyed engineered buildings that did not collapse (steel, concrete frame, 

and MBS), as well as engineered buildings that collapsed (BTS buildings), sustained 

significant damage to the building envelopes and interiors due to the combination of 

wind pressure, impacts by wind–borne debris, and subsequent water intrusion. 

Finding 17:	 The failure of building envelopes at St. John’s Regional Medical Center (SJRMC), 

which led to loss of protection and subsequent extensive damage to building interiors 

(affecting electrical distribution and fixtures, water and gas pipes, HVAC systems and 

ductwork, and the elevator system and elevator shaft enclosure), was the primary cause 

for the complete loss of functionality of this critical facility, which occurred despite the 

robust structural system that withstood the tornado without structural collapse. 

l NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

Executive Summary 

Finding 18:	 The majority of the impact–resistant windows on the fifth floor (Behavioral Health 

Unit) of the West Tower of SJRMC remained intact, whereas most regular dual–pane 

insulated windows at SJRMC were broken when exposed to the same tornado hazards. 

Finding 19:	 While there was no direct evidence that roof aggregate contributed to any fatalities in 

Joplin, there was evidence that roof aggregates contributed to envelope damage in 

SJRMC buildings and surrounding structures, thus adding to the tornado debris hazard 

and the potential for injuries or fatalities. 

 Performance of Shelters/Safe Rooms/Designated Refuge Areas 

Finding 20:	 NIST found that Joplin residents had limited access to underground or tornado–

resistant shelters. There were no community shelters or safe rooms in the City of 

Joplin or Jasper County at the time of the May 22, 2011, Joplin tornado. Also, 82 

percent of the homes in Joplin lacked basements. Only a few non–residential buildings 

were equipped with underground locations (e.g., basements), and none was identified 

as having a tornado–resistant shelter above ground. 

Finding 21:	 While many non–residential facilities had designated refuge areas, several of these 

areas suffered severe damage and NIST found no evidence that these areas yielded 

positive outcomes with respect to loss of life. Most high–occupancy commercial and 

critical facilities surveyed by NIST in the tornado–affected area (SJRMC, schools, and 

big–box stores) had in–facility designated refuge areas for tornadoes. However, the 

locations of these areas were not always based solely on structural considerations. 

There are currently no design standards, requirements, or best–practice guidelines for 

designating refuge areas within existing commercial or critical buildings.19 

Finding 22:	 Currently, there are optional model code provisions for the design of specially
 

purposed shelters, but such shelters are not required.
 

Finding 23:	 Based on a few instances observed in this tornado, in–home shelters did perform well 

and provided life–safety protection to the home owners. NIST found no statistics on 

how many of the 7,411 damaged residential structures had in–home tornado shelters. 

Objective 3. Determine the performance of lifelines as it relates to the continuity of operations 

of residential, commercial, and critical buildings 

Finding 24:	 All utilities (water, gas, power) were lost in the areas most damaged by the May 22, 

2011, Joplin tornado. The utility providers restored service to critical buildings 

(SJRMC, water treatment plant) within 24 hours. 

Finding 25:	 The failure of building envelopes at NIST–surveyed critical facilities, and resultant 

severe damage to their interior and internal lifeline distribution systems, was the 

primary cause of the facilities’ complete loss of functionality despite restoration of 

utility services within 24 hours. 

Limited guidance, focused on identifying best available refuge areas in schools, is available in FEMA P431, Tornado 

Protection: Selecting Refuge Areas in Buildings (http://www.fema.gov/media-library/assets/documents/2246?id=1563). 

NIST NCSTAR 3, Joplin Tornado Investigation li 

19 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Executive Summary 

Finding 26:	 In critical facilities constructed in Joplin prior to 1998, the design wind speed for high–

occupancy buildings was higher than that specified for buildings housing the facilities’

backup power generators. 

Objective 4. Determine the pattern, location, and cause of fatalities and injuries, and associated 

emergency communications and public response 

Finding 27:	 During the period from 1950 (i.e., the beginning of official tornado record keeping) 

through 2011, tornadoes caused approximately 5,600 fatalities in the United States. 

Within an 80–mile radius around Joplin, 233 deaths (including those caused by the 

Joplin tornado) were caused by tornadoes during the same period. 

Finding 28:	 The Missouri State Police attributed 161 deaths and the City of Joplin attributed more 

than 1,000 injuries to the Joplin tornado, which affected an area with an estimated 

population of 20,820. 

Finding 29:	 Of the 161 deaths resulting from this tornado, 155 (96 percent) were caused by impact–

related factors (i.e., multiple blunt force trauma to the body). The others were caused 

by stress–induced heart attacks, pneumonia, or lightning. 

 Emergency Communication Prior to May 22, 2011 

Finding 30:	 There was evidence of high false–alarm rates20 among the storm–based tornado 

warnings officially issued for Joplin. From 2005 through 2011, 78 percent (14 out of 

18) of the official tornado warnings issued for Joplin did not result in a verified 

tornado; this percentage was in line with the 2007–2011 national average storm–based 

tornado false–alarm rate of 74.7 percent. More recently, over the 5–year period from 

2007 through 2011, the Joplin area false–alarm rate increased to 92 percent. 

Finding 31:	 Despite public perception, no evidence was found of high false–alarm rates for Joplin’s 

outdoor siren system.21 Since 2007, the average rate of activation of the 25–siren 

outdoor warning system in Joplin was once per year (at most), not including the test 

activations (1 minute in duration) that occurred weekly. 

Finding 32:	 Joplin residents interviewed after the Joplin tornado believed that there had been a high 

number of false alarms in Joplin from official tornado warnings and the City’s outdoor

siren system prior to 2011, even though the siren activation rate was once per year (on 

average). 

20 The NWS defines a false alarm as an unverified tornado warning. In other words a tornado warning polygon for which no visual 

reports or damage indicators demonstrate that a tornado occurred during the valid time period of the warning. 

21 In this report, the false alarm rate for the siren system is defined as the activation of the siren system without the occurrence of a 

severe weather event in Joplin. 

lii NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

Executive Summary 

 Tornado History Prior to May 22, 2011 

Finding 33:	 Prior to 2011, the roughly 30–square–mile City of Joplin had experienced one tornado 

rated EF–2 or greater since 1950; this tornado occurred on May 5, 1971. However, 

also since 1950, 182 tornadoes rated EF–2 or higher had struck within an 80–mile 

radius of the City. 

Finding 34:	 Prior to the May 22, 2011, Joplin tornado, scientifically unfounded beliefs about 

tornado movements and the effects of regional topography contributed to a common 

public perception that the City of Joplin was immune to a direct tornado strike. 

 Emergency Communication on May 22, 2011 

Finding 35: Two official tornado warnings were issued on May 22, 2011. After the first official 

warning, Joplin’s sirens were sounded but no tornado occurred. After the second 

official warning, the siren system was sounded again, 4 minutes after the tornado 

touched down and almost exactly when the tornado entered the City of Joplin. Both 

siren soundings took the form of a continuous tone of 3 minutes duration. 

Finding 36:	 The function of an alert is to grab people’s attention before/during a disaster; while the 

function of a warning is to provide information about the event and how the public 

should respond. Both are necessary in an emergency. Joplin’s outdoor siren system, 

which could generally be heard indoors as well as outside, was the primary means by 

which individuals were alerted to a tornado event on May 22, 2011. Radio, television, 

and word of mouth were the primary means by which individuals were provided with 

warning information on May 22, 2011. 

Finding 37:	 The Joplin–Jasper County Reverse–9–1–1 telephone system was not used on May 22, 

2011, due to its inability to disseminate information in a timely manner. It had taken 

up to 3 hours to get emergency calls out during previous uses, so it is unlikely that the 

system would have worked in this tornado event. 

Finding 38:	 Functioning as an alerting system only, the outdoor sirens prompted many Joplin 

residents and visitors to seek further information on May 22, 2011. The multiplicity of 

information sources, and the conflicting information provided by those sources, added 

to the public’s confusion about the true hazard as additional information was sought. 

Finding 39:	 Across the country, there is no standard method for sounding outdoor public siren 

systems, which has led to variations in siren usage, activation procedures, and sounding 

patterns among U.S. communities. Also, there are no nationally accepted standard 

protocols for the issuance of an all–clear alert following a warning. 

 Public Response and Consequences on May 22, 2011 

Finding 40:	 Of the 155 impact–related fatalities, 135 (87 percent) involved persons who are known 

to have been located inside structures during the tornado. The structures in which these 

NIST NCSTAR 3, Joplin Tornado Investigation liii 
 

 

 

 

 

 

Executive Summary 

people died included both residential (59 percent of the 135 victims) and non–

residential (41 percent) buildings. 

Finding 41:	 Virtually all of the buildings in which the 135 impact–related fatalities occurred 

experienced maximum estimated winds associated with tornadoes rated EF–3 or 

higher. The exceptions were the Meadows Healthcare facility, where two of the deaths 

occurred, and five single–family homes that were the sites of six of the fatalities. 

Finding 42:	 The hospital towers at SJRMC did not provide life–safety protection for all occupants, 

even though the towers did not collapse. Twelve impact–related fatalities occurred in 

the hospital, four of which involved patients in intensive care units. 

Finding 43:	 Responses to the approaching tornado among members of the public, in many cases, 

were delayed or incomplete, as was evidenced by the fatalities that occurred among 

individuals located outdoors, in vehicles, or en route within buildings to safer refuges 

when the tornado hit. 

Finding 44:	 Two factors were found to have contributed to the delayed or incomplete public 

response to the Joplin tornado. The first was a lack of awareness of the tornado. The 

second was an inability to perceive personal risk due to one or more of the following: 

receipt of conflicting or uncertain information about the tornado; pre–existing beliefs 

about Joplin’s immunity to direct tornado strikes; and distrust of or confusion about 

Joplin’s emergency communications system.

Finding 45:	 The main factor that convinced individuals to take shelter was the receipt of high–

intensity cues, including hearing or seeing the tornado approaching or witnessing 

others’ urgency related to taking protection.

Finding 46:	 No fatalities occurred in demolished, detached homes in which people took refuge in 

basements. Additionally, NIST found no evidence that any of those killed were located 

underground during the tornado. 

Finding 47:	 A disproportionate number of people aged 60 years or older died or were injured as a 

result of this tornado. NIST analysis of the fatalities resulting from the Joplin tornado 

shows that approximately 8 fatalities occurred per thousand people in Joplin aged 60 

years and over compared with 2 fatalities per thousand people in Joplin under 60 years. 

This disproportionate result remains even after removing all hospital and nursing home 

deaths. Factors that may have contributed to this outcome include a lack of 

information flow to these individuals, a lack of supportive social networks among 

individuals, or inability of an individual to withstand or recover from tornado–induced 

trauma. 

liv NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

Executive Summary 

E.5 RECOMMENDATIONS 

As part of its technical investigation of the Joplin tornado, NIST has developed 16 recommendations for 

improving tornado hazard characterization, for improving how buildings and shelters are designed, 

constructed, and maintained in tornado–prone regions, and for improving the emergency communications 

that warn of imminent threats from tornadoes. These recommendations are listed in Table E–1, below, in 

three groups that reflect the objectives and findings of the investigation. 

Group 1 contains recommendations relating to the characteristics of tornado hazards and their associated 

wind fields. The recommendations in Group 2 concern the performance of buildings, lifelines, and 

shelters and designated safe areas. Group 3 recommendations relate to findings about the pattern, 

locations, and causes of tornado fatalities and injuries, the performance of emergency communications 

systems, and the public response to this tornado. 

The recommendations call for action by specific entities with regard to the development, adoption, and 

enforcement of standards, codes, and regulations; professional and construction practices, education, and 

training; and research and development. NIST believes that these recommendations are realistic and 

appropriate, and are achievable within a reasonable period of time. 

NIST strongly urges State and local authorities having jurisdiction to adopt and enforce model building 

codes and standards. Enforcement is critical to ensuring expected levels of safety. Following good 

building practices also is critical to achieving better performance of structures during extreme events like 

tornadoes. 

NIST NCSTAR 3, Joplin Tornado Investigation lv 
 

 

 

 

 

Executive Summary 

Table E–1. Summary of NIST recommendations. 

Organization with Lead 

Responsibility for Interested Parties Implementation 

Group 1: Tornado Hazard Characteristics and Associated Wind Field 

Recommendation 1: NIST recommends that a capacity be developed and deployed that can Academia, DOE, NOAA 

measure and characterize actual tornadic wind fields, including near–surface wind fields, for use in NOAA/NWS, NRC, NSF 

the engineering design of buildings and infrastructure. This would require enhancement and 

widespread deployment of cost-effective, advanced technologies, including weather radar. 

Recommendation 2: NIST recommends that information gathered and generated from tornado Academia, FEMA, NGA NWS 

events (such as the Joplin tornado) should be stored in publicly available and easily accessible 

databases to aid in the improvement of tornado hazard characterization. 

Recommendation 3: NIST recommends that tornado hazard maps for use in the engineering design ASCE, DOE, FEMA, ICC, NIST 

of buildings and infrastructure be developed considering spatially based estimates of the tornado NRC 

hazard instead of point–based estimates. 

Recommendation 4: NIST recommends that new damage indicators (DIs) be developed for the Academia, ATC, FEMA, NWS 

Enhanced Fujita tornado intensity scale to better distinguish between the most intense tornado NRC, NSF, OSTP 

events. Methodologies used in the development of new DIs and associated degrees of damage 

(DODs) should be, to the extent possible, scientific in nature and quantifiable. As new information 

becomes available, a committee comprised of public and private entities should be formed with the 

ability to propose, accept, and implement changes to the EF Scale. The improved EF Scale should be 

adopted by NWS. 

Recommendation 

lvi NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

Executive Summary 

Organization with Lead 

Responsibility for Interested Parties Implementation 

Group 2: Performance of Buildings, Shelters, Designated Safe Areas, and Lifelines 

Recommendation 5: NIST recommends that nationally accepted performance–based standards for Academia, ATC, Design ASCE 

the tornado–resistant design of buildings and infrastructure be developed and adopted in model and construction 

codes and local regulations to enhance the resiliency of communities to tornado hazards. The industry (including ACI, 

standards should encompass tornado hazard characterization, performance objectives, and AISC, AWS, NAHB, PCA, 

evaluation tools. The standards shall require that critical buildings and infrastructure such as SDI, SJI, TMS), FEMA, 

hospitals and emergency operations centers be designed to remain operational in the event of a ICC, NFPA 

tornado. 

An example of a tornado performance objectives matrix for buildings of different risk categories is 

shown below: 

Risk Cat. * IV Facilities 

Risk Cat. * III 

Risk Cat. * II 

(1) Hardened area, shelter–in–place. 

(2) Public shelter. 

* Risk Categories based on ASCE 7–10. 

Recommendation 

NIST NCSTAR 3, Joplin Tornado Investigation lvii 
 

 

 

 

 

 

Executive Summary 

Recommendation Interested Parties 

Organization with Lead 

Responsibility for 

Implementation 

Recommendation 6: NIST recommends the development of risk–balanced, performance–based 

tornado design methodologies such that all building components and systems meet or exceed the 

same performance objectives when subjected to tornado hazards. 

Academia, ASCE, ATC, 

Design and 

construction industry 

(including ACI, AISC, 

AWS, NAHB, PCA, SDI, 

SJI, TMS), ICC, NFPA 

NIST, FEMA 

Recommendation 7: NIST recommends that: (a) a tornado shelter standard specific for existing 

buildings be developed and referenced in model building codes; and (b) tornado shelters be 

installed in new and existing multi–family residential buildings, mercantile buildings, schools and 

buildings with assembly occupancies located in tornado hazard areas identified in the performance –

based standards required by Recommendation 5. 

Academia, FEMA, 

NAHB, NFPA, States 

and authorities having 

jurisdiction (AHJ) in 

tornado–prone areas 

ICC 

Recommendation 8: NIST recommends the development and implementation of uniform national 

guidelines that enable communities to create safe and effective public sheltering strategies. The 

guidelines should address planning for siting, designing, installing, and operating public tornado 

shelters within the community. 

IAEM, IAFC, ICC, NAC, 

NCSL, NEMA, NFPA, 

NSF, NWS 

FEMA 

Recommendation 9: NIST recommends that uniform guidelines be developed and implemented 

nationwide for conducting assessment of tornado risk to buildings and designating best available 

tornado refuge areas as an interim measure within buildings until permanent measures fully 

consistent with Recommendations 5 and 7 are implemented. 

Academia, DHS S&T, 

IAEM, IAFC, ICC, NAC, 

NCSL, NEMA, NFPA, 

States and AHJs in 

tornado–prone areas 

FEMA 

Recommendation 10: NIST recommends that aggregate used as surfacing for roof coverings and 

aggregate, gravel, or stone used as ballast be prohibited on buildings of any height located in a 

tornado–prone region. 

ASCE, NFPA, SPRI, 

States and AHJs 

ICC 

lviii NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

Executive Summary 

Organization with Lead
 

Responsibility for
 

Implementation
 

Recommendation 11: NIST recommends that enclosures of egress systems (elevators, exits, BOMA ICC, NFPA 

stairways) in critical facilities in tornado–prone areas be designed to maintain their functional 

integrity when subjected to tornado hazards. 

Recommendation 12: NIST recommends that (a) tornado vulnerability assessment guidelines for BOMA, DHS IP, DHS FEMA 

critical facilities be developed and (b) owners and operators of existing critical facilities in tornado– S&T, IFMA, NFPA, 

prone areas perform tornado vulnerability assessments, which includes steps to protect the States and AHJs 

functionality of (1) backup power supplies, (2) vertical movement within the building (elevator 

equipment and shaft enclosures), and (3) means of egress illumination (battery–powered lighting in 

addition to backup power), in a tornado event. 

Group 3: Pattern, Location, and Cause of Fatalities and Injuries, and Associated Performance 

of Emergency Communications Systems and Public Response 

Recommendation 13: NIST recommends the development of national codes and standards and Academia, FEMA, NFPA 

uniform guidance for clear, consistent, recognizable, and accurate emergency communications, IAEM, ICC, NEMA, and 

encompassing alerts and warnings, to enable safe, effective, and timely responses among NWS 

individuals, organizations, and communities in the path of storms having the potential to create 

tornadoes. 

NIST also recommends that emergency managers, the NWS, and the media develop a joint plan and 

take steps to make sure that accurate and consistent emergency alert and warning information is 

communicated in a timely manner to enhance the situational awareness of community residents, 

visitors, and emergency responders affected by an event. 

Recommendation Interested Parties 

NIST NCSTAR 3, Joplin Tornado Investigation lix 
 

 

 

 

 

Executive Summary 

Organization with Lead
 

Responsibility for
 

Implementation
 Recommendation Interested Parties 

Recommendation 14: NIST recommends that the full range of current and next–generation 

emergency communication “push” technologies (e.g., GPS–based mobile alerts and warnings, 

reverse 9–1–1, outdoor siren systems with voice communication, NOAA weather radios) be 

deployed and utilized to maximize each individual’s opportunity to receive emergency information

and respond safely, effectively, and in a timely fashion. 

Academia, DHS, FCC, 

IAFC, NEMA, NFPA, 

NWS 

FEMA 

Recommendation 15: NIST recommends research be conducted to identify the factors that will 

significantly enhance public perception of personal risk and promote rapid and effective public 

response during emergencies, including tornadoes. 

Academia, DHS, ICC, 

NFPA, NWS 

NSF, NIST 

Recommendation 16: NIST recommends that technology be developed to provide tornado threat 

information to emergency managers, policy officials, and the media on a spatially resolved real–time 

basis to supplement the currently deployed official binary warn/no warn system. 

FEMA, IAEM, Media 

industry, NEMA, NFPA 

NOAA 

Key: ACI, American Concrete Institute; AHJ, authority having jurisdiction; AISC, American Institute of Steel Construction; ASCE, A merican Society of Civil 

Engineers; ATC, Applied Technology Council; AWS, American Welding Society; BOMA, Building Owners and Managers Association International; DHS, U.S. 

Department of Homeland Security; DHS IP, DHS Office of Infrastructure Protection; DHS S&T, DHS Science and Technology Directorate; DOE, U.S. Department 

of Energy; FCC, Federal Communications Commission; FEMA, Federal Emergency Management Agency; IAFC, International Association of Fire Chiefs; IAEM, 

International Association of Emergency Managers; ICC, International Code Council; IFMA, International Facility Managers Association; NAC, National 

Association of Counties; NAHB, National Association of Homebuilders; NCSL, National Conference of State Legislators; NEMA, National Emergency 

Management Association; NFPA, National Fire Protection Association; NIST, National Institute of Standards and Technology; NOA A, National Oceanic and 

Atmospheric Administration; NRC, U.S. Nuclear Regulatory Commission; NSF, National Science Foundation ; NWS, National Weather Service; PCA, Portland 

Cement Association; SDI, Steel Deck Institute; SJI, Steel Joist Institute; SPRI, Single Ply Roofing Industry; TMS, The Masonry Society. 

lx NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

Executive Summary 

E.6 REFERENCES 

ANSI/ANS (American National Standards Institute/American Nuclear Society). 2011. Estimating 

Tornado, Hurricane, and Extreme Straight Line Wind Characteristics at Nuclear Facility Sites. 

ANSI/ANS–2.3–2011. American Nuclear Society. La Grange Park, IL. 

DOE (U.S. Department of Energy). 2002. Natural Phenomena Hazards Design and Evaluation Criteria 

for Department of Energy Facilities. DOE–STD–1020–2002. Washington, DC, January. 

FEMA (Federal Emergency Management Agency). 2008a. Taking Shelter from the Storm: Building a 

Safe Room for Your Home or Small Business. FEMA P–320, Third Edition. Washington, DC, 

August. 

FEMA (Federal Emergency Management Agency). 2008b. Design and Construction Guidance for 

Community Safe Rooms. FEMA P–361, Second Edition. Washington, DC, August. 

ICC/NSSA (International Code Council/National Storm Shelter Association). 2008. ICC/NSSA Standard 

for the Design and Construction of Storm Shelters. ICC 500–2008, American National Standard. 

Washington, DC, June. 

NIST (National Institute of Standards and Technology), 2013. Preliminary Reconnaissance of the May 

20, 2013, Newcastle-Moore Tornado in Oklahoma. NIST Special Publication 1164. Gaithersburg, 

MD, December. 

NRC (U.S. Nuclear Regulatory Commission). 2007. Design Basis Tornado and Tornado Missiles for 

Nuclear Power Plants. NRC Regulatory Guide (NRC/RG) 1.76. Washington, DC. 

NWS (National Weather Service). 2011. NWS Central Region Service Assessment Joplin, Missouri, 

Tornado—May 22, 2011. Silver Spring, MD. 

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Chapter 1 

INTRODUCTION

1.1 THE CITY OF JOPLIN 

The City of Joplin, which bore the brunt of the powerful tornado that struck Missouri on May 22, 2011, is 

located in southwest Missouri, as shown in Fig. 1–1. Joplin is considered the center of what is regionally 

known as the “four–State area,” because it is the most centrally located city in the area where the States of 

Arkansas, Kansas, Missouri, and Oklahoma touch. Incorporated in 1873, the city is Missouri’s fourth 

largest metropolitan area22, with a population of 50,150.23 Joplin spans both Jasper and Newton 

Counties, covering a total of 31.54 square miles. The dividing line between the two counties runs along 

32nd Street (see Fig. 1–2), with Jasper County to the north and Newton County to the south. 

Figure 1–1. Location of Joplin (circled in red) in southwestern Missouri. 

22 Joplin Area Chamber of Commerce (http://www.joplincc.com/whywedoit.html).
 

23 United States Census Bureau 2010 estimate (http://quickfacts.census.gov/qfd/states/29/2937592.html).
 

NIST NCSTAR 3, Joplin Tornado Investigation 1 
 

 

 

 

Chapter 1 

Figure 1–2. Map of Joplin and surrounding area. 

Since 1954, the City has operated under the council–manager form of government. There is a governing 

city council that is responsible for passing ordinances, adopting a budget, appointing committees, and 

hiring higher–level city officials. The City manager is responsible for carrying out the policies and 

ordinances of the council, overseeing day–to–day operations of the City, and appointing heads of City 

2 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 1 

departments. Some planning and management functions are operated jointly between the City and Jasper 

County, including the Joplin/Jasper County Emergency Management Agency. 

Joplin is a commercial, medical, and cultural hub for the four–State region.24 There are two hospitals 

located within the city limits, Freeman Health Systems and St. John’s Regional Medical Center (SJRMC), 

which provide health care and employment for thousands of local residents, as well as facilities 

specializing in sports medicine, psychological and psychiatric services, and heart and cancer care. Three 

other hospitals are located near Joplin: McCune–Brooks Hospital in Carthage, Missouri (14 miles away); 

Freeman Neosho Hospital in Neosho, Missouri (15 miles away); and Via Christi Hospital Pittsburg Inc. in 

Pittsburg, Kansas (26 miles away). Nursing and retirement centers and extended care facilities are also a 

part of the Joplin area. 

Joplin is home to three airports: Joplin Regional Airport (shown at the far north of Fig. 1–2); Five Mile 

Airport; and a heliport at SJRMC. There are six post–secondary educational institutions located 

throughout the City. The largest is Missouri Southern State University (MSSU), a State school with more 

than 4,000 students. Others include Vatterott College, Ozark Christian College, Franklin Technology– 

MSSU, Messenger College, and New Dimensions School of Hair Design. Joplin has one public high 

school, Joplin High School, and three private high schools. Like any densely populated city, Joplin has 

its share of restaurants, shops, hotels, sports and entertainment venues, conference facilities, and other 

commercial properties. 

Due to its centralized location, Joplin makes an attractive home for a number of industries, including 

manufacturing, retail trade, construction, and transportation.25 Area employers provide jobs in food 

processing, metal fabrication, equipment manufacturing, plastics and packaging technologies, customer 

service, and retail sales. Goods distribution centers, administrative offices, machinery repair facilities, 

and custom computer–programming services are fueling economic growth in the region. As the regional 

economic hub, Joplin’s population increases by five times during each workday, making for a daytime 

population of 250,000 people.26 

Summary demographic information from the United States Census Bureau indicates that the median age 

among Joplin residents is 35 years, and that 14.8 percent of residents are aged 65 or older.27 The City is 

essentially split evenly by gender (52 percent of residents are women), and is predominantly (87.6 

percent) white. With regard to educational levels, 84.3 percent of Joplin residents aged 25 or older have 

received at least a high school diploma. The number of households in Joplin totaled 20,552 in 2011, with 

an average of 2.33 persons per household. More than half (53 percent) of the City’s population (over the 

age of 15) is married, with 23.4 percent never married and the rest separated (2.9 percent), widowed (7.8 

percent), or divorced (13.0 percent).28 

Joplin sits within the Ozark Plateau (the Ozarks), which is a heavily forested group of highlands in the 

south central portion of the United States.29 Although the plateau extends from St. Louis, Missouri, to the 

24 Joplin Area Chamber of Commerce (http://www.joplincc.com/joplinhistory.html). 

25 Ibid. 

26 Joplin Area Chamber of Commerce (http://www.joplincc.com/whywedoit.html). 

27 United States Census Bureau (http://quickfacts.census.gov/qfd/states/29/2937592.html). 

28 Citi–Data.com (www.city–data.com/city/Joplin–Missouri.html#ixzz2Kzi6gTDD).
 29 Arkansas Geological Survey (www.geology.ar.gov/education/ozark_plateaus.htm); Encyclopedia Britannica
 

(http://www.britannica.com/EBchecked/topic/437144/Ozark–Mountains). 

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Arkansas River, it is divided into three different plateau surfaces: the Springfield Plateau; the Salem 

Plateau; and the Boston Mountains Plateau. Joplin is located within the Springfield Plateau, which is 

characterized by gently rolling hills (or undulating topology) above ground, and caves and sinkholes, 

common in limestone below ground. The Ozarks also contain deposits of lead, zinc, iron, and barite ores. 

Development in Joplin initially began because of lead mining; however, it was the discovery of zinc that 

spurred the growth of Joplin in the early 20th century. Most of the mines were closed after World War II, 

leaving mine workings under nearly 75 percent of the city. 

Due to the many near–surface mine tunnels30 and other unfavorable soil conditions (high water table and 

limestone just below the surface31), most of the homes in Joplin (83 percent32) do not have basements. 

Additionally, very few residences in Joplin have tornado shelters or safe rooms.33 In contrast, public 

safety guidance from the National Weather Service (NWS)34 indicates that underground shelters, 

basements or safe rooms are the safest places in a tornado. 

Residents in the Joplin area are no strangers to tornadic activity given the area’s proximity to tornado 

alley.35 Statistics gathered by the NOAA/NWS Storm Prediction center (SPC) indicate that between 1950 

and 2011, the area within an 80–mile radius of Joplin experienced a total of 766 tornadoes, an average of 

12.5 per year. Of these, 24 percent were rated EF–2 or greater on the Enhanced Fujita Scale,36 and 6 

percent were rated EF–3 or greater. 

There have been very few instances, however, of significant tornadoes striking within the City of Joplin. 

Prior to May 22, 2011, only one tornado rated EF–2 or greater had struck Joplin since official record– 

keeping began in 1950. On May 5, 1971, a tornado spawned by violent thunderstorms touched down in 

Joplin at about dusk. This tornado was one of many that struck Oklahoma, Arkansas, Kansas, Nebraska, 

and Iowa that day, and was one of at least 14 confirmed tornadoes in southwestern Missouri. The tornado 

damaged a 37–block section of the City, injuring 45 persons, killing 1, and causing an estimated $7 

million in damage (1971 dollars). The 1 fatality occurred when the tornado struck the Anderson Mobile 

Trailer Court, where 15 trailers were destroyed. Ten residences and at least three other mobile homes 

were reported to have been destroyed in the storm. Additionally, 60 other homes and 22 businesses were 

heavily damaged, and another 320 homes sustained minor damage. News accounts at the time indicated 

that the tornado sirens were not sounded until the tornado had already touched down and was moving 

through the City. The National Severe Storms Forecast Center issued a tornado warning and notified the 

Joplin police at 6:15 p.m. CDT. However, the sirens were not sounded until 38 min later at 6:53 p.m., 

when a Joplin police officer on patrol witnessed debris flying through the air. At the time, the standard 

operating procedure in most communities was to sound the sirens when the tornado warning was issued, 

because a “warning indicated that a tornado had been sighted in or near the area of the warning.” Damage 

from the 1971 storm is shown in Fig. 1–3. 

30 NIST Interview with City of Joplin Building Official and Code Enforcement Supervisor
 

31 Reuters (www.reuters.com/article/2011/05/31/us–tornado–basements–idUSTRE74U6HT20110531). 32 Data from Jasper County Assessor’s office.
 

33 NIST Interview with City of Joplin Building Official and Code Enforcement Supervisor
 

34 NOAA (http://www.nws.noaa.gov/om/severeweather/resources/ttl6–10.pdf).
 

35 “Tornado Alley is a nickname given to an area in the southern plains of the central U.S. that consistently experiences a high
 

frequency of tornadoes each year.” NOAA (http://www.ncdc.noaa.gov/oa/climate/severeweather/tornadoes.html#alley). 

36 The Enhanced Fujita (EF) Scale is used by the NWS to rate the intensity of the maximum wind speeds in a tornado based on 

observed damage, with EF–0 being the lowest (beginning with winds of 65 mph or more) and EF–5 the highest (winds exceeding 

200 mph). See http://www.spc.noaa.gov/efscale/ and Secs. 2.3.4.1 and 2.5 for more information. 

4 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 1 

© C.F. Boone Publications. 

Used with permission. 

Figure 1–3. Damage from the 1971 Joplin tornado.37 

The relative lack of tornado strikes within the city was one of the factors that led to a false impression 

among many Joplin residents that tornadoes would not strike the City. Many believed that tornadoes 

would not track directly through the City, but instead would track only to the north or south of the City, 

missing Joplin completely. Some believed that the topography around Joplin had something to do with 

tornado tracking, protecting the city from direct hits. However, the 1971 tornado demonstrated that Joplin 

was not immune to tornado strikes. 

The prevalence of tornado–related false alarms in Joplin and surrounding areas also fed the notion that 

tornadoes would not strike the City. Over a period of 7 years (from 2005 to 2011), Joplin experienced a 

78 percent false alarm rate,38 and although similar to the NWS national average (74 percent), nearly 8 out 

of 10 tornado warnings in Joplin were not followed by tornadoes. Additionally, prior to May 22, 2011, 

sirens in Joplin were audibly tested on a weekly basis and also sounded on average once per year for non– 

tornadic high–wind events, potentially resulting in further desensitization among residents. 

37 From Baron, H. (Ed.). 1971. The Joplin Tornado. Boone Publications. Available online at 

www.joplinpubliclibrary.org/digitized/joplin_tornado_booklet.php. 38 The NWS defines a false alarm as an unverified tornado warning. In other words, a tornado warning polygon for which no visual 

reports or damage indicators demonstrate that a tornado occurred during the valid time period of the warning. 

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1.2 

Chapter 1 

THE EVENT 

Following is an account of the Joplin tornado and its impacts on the community. Data and information 

supporting this reconstruction of the events of May 22, 2011 were collected from many sources, including 

through site visits, interviews with residents and survivors of the tornado, government officials, and 

others. Details of the collected data and subsequent analyses, along with any associated assumptions and 

uncertainties, are reported in Chapters 2 through 4. 

In the days leading up to the Joplin tornado of May 22, 2011, forecasters at the SPC in Norman, 

Oklahoma, were becoming more confident that a significant weather event was approaching that would 

include thunderstorms and possibly tornadoes for a region that included Joplin. On Sunday, May 22, 

2011, the SPC issued a tornado watch for Joplin and surrounding communities at 3:00 p.m. Although 

conditions favoring thunderstorms were present in the region, conditions in Joplin itself were relatively 

quiescent at this time. Joplin residents and visitors engaged in normal activities throughout the City in the 

afternoon hours. At home, residents spent time watching television—mostly news or cable 

programming—eating or preparing dinner, doing chores, getting ready to leave (for work or church, for 

example), or sleeping. Some were monitoring the weather, checking radar via the Internet or switching 

back and forth between the Weather Channel and local news or weather reports on television. Outside of 

homes, individuals were working the afternoon/evening shifts at local restaurants, businesses, and 

hospitals; completing their Sunday errands (often with the vehicle radio on); visiting friends or family; or 

attending local worship services or religious classes. Additionally, 6,000 to 7,000 people were attending 

the high school’s graduation ceremony at MSSU in northwest Joplin. 

Thunderstorms eventually did form in the region, and at approximately 5:00 p.m., storms to the west of 

Joplin began to intensify. At 5:09 p.m., a storm developed signs of rotation and the NWS issued a 

tornado warning. Individuals in and around Joplin who were tuned into television programming or radio 

broadcasts most likely received word of this warning, as the Emergency Alert System was activated to 

accompany the tornado warning. Although the tornado warning was disseminated via NOAA Weather 

Radio broadcasts and media–delivered mobile text –based services, their use by the public was not 

prevalent in Joplin. Also, the Joplin–Jasper County Reverse–9-1-1 system was not used due to the time 

required for its operation. Although the 5:09 p.m. tornado warning pertained mostly to areas outside of 

Joplin, a small portion of northeast Joplin was included in the coverage area. A few minutes later, at 5:11 

p.m., the 25–siren alert system was activated throughout Joplin (when one or more sirens are sounded, all 

25 must be sounded). The decision to sound the siren system was made by the Joplin–Jasper County 

emergency manager based on conversations between emergency management personnel in Cherokee 

County, Kansas (immediately west of Jasper County) and Joplin–Jasper County, information received 

from the NWS about the impending (5:09 p.m.) warning affecting northeast Joplin, the direction of travel 

of the storm that was the subject of the 5:09 p.m. warning, and anecdotal information from a local 

emergency official (outside of Joplin) regarding the destruction associated with that storm. The outdoor 

sirens sounded a single continuous tone for 3 min. The length and sound patterns of this continuous tone 

vary from those of other communities in the United States, and there is no standard method for sounding 

outdoor public warning systems in the United States. 

Although Joplin’s siren system was intended to alert individuals located outdoors of impending severe 

weather, many individuals who were indoors also heard the sirens. The sirens could be heard in stores, 

places of worship, nursing homes, entertainment facilities, and other structures. However, many stores 

6 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 1 

had managers on duty monitoring the weather even before the sirens sounded. Some larger stores, such 

as Home Depot, had procedures in place under which managers received custom alerts to provide early 

notification of weather emergencies. Store managers relayed important sheltering information to patrons, 

in larger stores via public address systems. Similarly, SJRMC relayed weather information and sheltering 

instructions, under a procedure known as Condition Gray, when the head nurse verified that sirens were 

sounding in Joplin. Staff, patients, and visitors were informed that there was severe weather in the area, 

and that patients were to be moved from their rooms, if possible, into interior hallways. The sirens could 

also be heard inside residential structures, including multi–family and single–family homes. In addition, 

some portion of the residents in homes was already monitoring weather information via television or 

radio. 

Regardless of their location, individuals frequently attempted to confirm the weather–related information 

they received through additional sources. Persons first alerted by the outdoor siren system, for example, 

often consulted media sources, other people, or their physical environment (i.e., by looking outside for 

any indication of bad weather) for confirmation that a tornado was actually upon them. Unfortunately, 

early in the warning process, confirmation was almost impossible. All warning information provided 

prior to 5:17 p.m. related to a storm that weather forecasters were tracking to the north of Joplin, that was 

heading toward Webb City or Carl Junction (Missouri communities located north of Joplin). Around this 

same time, the environment offered very little in the way of cues of an impending storm, also making it 

difficult to confirm the tornado risk. People looking to the sky saw only clouds that did not look as 

menacing as those that would normally accompany a tornado. The lack of confirming cues, complicated 

by the public’s perception that tornadoes tended to track around Joplin, caused many Joplin residents to 

feel that they were not at risk. Some continued to monitor the weather, however, while others did not. 

A number of storms continued to develop to the south and west of the storm that was the subject of the 

5:09 p.m. tornado warning, and at 5:17 p.m., another possible tornado was indicated on radar. 

Consequently, another tornado warning (the 18th affecting Joplin since 2005) was issued by the NWS, 

and this time the coverage area included the entire City of Joplin. Although the radar indicated a possible 

tornado on the ground, it could not initially detect the potential severity of the tornado because of the 

limitations of radar coverage in this region. 

Around the time of the second NWS tornado warning at 5:17 p.m., Joplin residents who had continued to 

monitor the weather do not recall receiving confirming evidence of a tornado. First, the outdoor siren 

system was not activated again for the 5:17 p.m. warning, probably because Joplin’s emergency manager 

had already sounded the system 6 min earlier (for the storm that had threatened northeastern Joplin). 

Additionally, the media continued to report on storms said to be passing to the north and missing Joplin, 

or moving away from the City. Others recall announcers continually discussing a tornado between Carl 

Junction and Webb City, or news of a tornado that had hit a small town in Kansas. 

Meanwhile, skies to the west of Joplin darkened further, the base of the clouds lowered, and based on 

reports from police observing the storm and video evidence on the ground, a tornado (initially with 

multiple vortices) touched down just to the west of Joplin’s city limits at approximately 5:34 p.m. In the 

vicinity of the initial touchdown and during the ensuing few minutes, trees were uprooted and snapped 

and sporadic damage occurred to the residences in the few subdivisions in the area (Fig. 1–4). Around 

this time, wind speeds at Joplin Regional Airport, the location of the lone wind speed measuring device, 5 

miles to 6 miles away from the tornado center, began to increase to over 40 mph and would continue to be 

NIST NCSTAR 3, Joplin Tornado Investigation 7 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 1 

this high at this location for the remainder of the time the tornado was in the City of Joplin. The airport’s 

consistent wind speed measurement indicated that the Joplin tornado affected a large spatial area and 

subjected the area to strong winds over a long period of time. 

Damaged 

Residential Area

Tree Fall

Tree Fall

Newton Road

S. Country Club Dr.

0 0.1 0.2 0.3 0.4 0.5

Miles

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 1–4. Initial damage in the Joplin tornado. Yellow arrows indicate directions of 

treefall. Possible multiple vortices shown by red arrows. 

As the storm and the tornado moved in an eastward direction toward the city limits of Joplin, the tornado 

began to merge into one large, counterclockwise-rotating vortex and rapidly increase in size.39 At 

approximately 5:38 p.m., public awareness of the situation had begun to increase substantially as the 

tornado had now entered the City of Joplin. The Joplin–Jasper County emergency manager decided to 

sound Joplin’s 25–siren system a second time at 5:38 p.m. Even though Joplin–Jasper County emergency 

procedures did not specify the use of a second warning, the decision to sound the sirens a second time was 

based upon discussions between Joplin–Jasper County Emergency Management and the Joplin Fire 

Department regarding an NWS statement on the size and intensity of the tornado. Also, around this time, 

television and radio stations were reporting weather information that caused people in Joplin to take 

notice. The media reported that a tornado had touched down just to the west of Joplin at Iron Gates, 

Missouri. NBC’s KSNF–TV, which was equipped with a tower camera, showed video footage of the 

imminent tornado strike and pleaded with its listeners to “Take cover now!” 

The tornado approached Schifferdecker Avenue, a north–south road on the western edge of the city that 

bordered the heavily populated areas of Joplin. Wind speeds began to rapidly increase along 

Schifferdecker Avenue as the tornado grew closer, and trees began to sway, bend, and fall inward towards 

the tornado. A driver in this area recalled seeing a wall of water that he assumed was simply straight–line 

winds, until he drove into it. Trees were falling down all around his car and limbs 2 in. to 4 in. in 

diameter were dragged across the road in front of him. An estimated 10,000 trees fell due to the tornado, 

an indicator of the size and power of this event. The tornado caused its first significant damage to a 

subdivision immediately to the west of Schifferdecker Avenue, creating a lot of debris as a result. The 

tornado also claimed its first fatality around this time in a vehicle on Schifferdecker Avenue. 

39 All references to the size of the tornado are based upon the tree–fall analysis discussed in Chapter 2 of this report. 

8 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 1 

This death on Schifferdecker Avenue would be the first of 161 fatalities resulting from the Joplin 

tornado40 . Moving in an east–northeasterly direction, the tornado proceeded to damage other highly 

populated areas on the east side of Schifferdecker (see Fig. 1–5), including a residential neighborhood 

that comprised ranch–style homes, with basements, built primarily during the early 1980s. Although 

these homes were damaged significantly, no one was killed in this neighborhood. 

Elks Lodge

0 0.1 0.2 0.3 0.4 0.5

Miles

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 1–5. Damage on the west side of Joplin. 

One–half mile northwest of that early 1980s neighborhood, a man took refuge in the bathroom of the 

single–family home he was renting. After tracking the storm online and hearing the second siren, he had 

decided that protective action was necessary. Within minutes, he could hear the tornado tearing the house 

apart, and was thrown into the air and landed in his backyard. Located next door was one of the first 

non–residential structures that the tornado had encountered in Joplin, the St. Paul’s United Methodist 

Church. The storm completely destroyed the envelope (i.e., exterior walls and roof) of St. Paul’s Mass 

Hall building, leaving only the pre–engineered structural frame of the building intact. 

The tornado continued to increase in size and changed direction from slightly north of east to due east 

along 26th Street, continuing to wreak havoc on residential areas in its path. Because there were no 

community storm shelters in Joplin and only 18 percent of homes had basements, residents in homes 

without basements reportedly took shelter in internal (or centrally located) bathrooms, closets, laundry 

rooms, or hallways of their homes. Very few residents had in–home shelters. Those who did and were in 

the storm’s path survived in these pre–manufactured shelters while their wood–framed homes were 

destroyed around them. 

Upon reaching the eastern end of the residential area, the tornado impacted another non–residential 

building, the Joplin Elks Lodge. Someone had just entered the building, shouting about the approaching 

40 Earlier fatality estimates made by the NWS following the May 22, 2011, Joplin tornado listed the death toll at 158. This report also 

counts 3 indirect fatalities for a total of 161. 

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Chapter 1 

tornado, and all five individuals inside the building had started to run for the kitchen’s walk–in cooler. 

None made it to the cooler before the tornado completely demolished this wood–framed structure. Four 

of the five occupants died, of impact–related causes. 

A few minutes later, at approximately 5:40 p.m., the tornado approached an area with a number of 

medical and office buildings (Fig. 1–6). Centered around the intersection of 26th Street and Maiden 

Lane, this area included several small commercial office buildings, such as the Ramesh Shah 

Ophthalmology Center, as well as SJRMC and Mercy Village Apartments (an assisted–living complex 

near the east side of SJRMC). SJRMC was vitally important to the region, providing jobs to more than 

1,700 people and care for 140,000 area residents.41 The facility comprised two complexes, each with 

several buildings that housed different medical services and doctors’ offices. Most notable structurally 

were the West Tower, a seven–story reinforced concrete building constructed in 1965, and the East 

Tower, a nine–story steel structure built in 1985, both of which contained inpatient rooms. The towers 

were the tallest buildings in the immediate area. Other structures at SJRMC included the Emergency 

Generator building, the Chiller Plant building, the Oncology Clinic building, and three medical office 

buildings. 

Located just south of the estimated center of the tornado track, SJRMC likely experienced some of the 

storm’s highest winds as well as significant impacts from windborne debris. Besides demolishing the 

Emergency Generator building and thus destroying SJRMC’s ability to function on backup power, the 

tornado severely damaged the windows, doors, walls, and roofs of the other buildings at SJRMC, 

including the two towers. Failure of the building envelopes subsequently allowed strong wind, water, and 

windborne debris to penetrate the building interiors and damage their contents, walls, ceilings, and 

building systems (e.g., electrical, mechanical, plumbing, elevators). The extensive damage rendered this 

critical facility completely nonfunctional, despite the fact that most of its buildings were able to withstand 

the strong winds without structural collapse. 

Failure of the building envelopes at SJRMC also put the 183 patients and staff who were at the hospital 

on May 22, 2011, in extreme danger of bodily harm. Many of the patients, visitors, and staff who were in 

the two towers during the tornado had taken shelter in internal hallways in preparation for the storm. 

They recalled hearing doors blow open as the tornado hit, which sent everything from one end of the hall 

flying into the other end. Survivors were hit with medical equipment, hospital furniture, ceiling tiles, 

broken glass, hailstones, and other windborne debris. Due to the complete loss of power and the amount 

of damage and debris, the staff quickly realized that the facility could no longer provide proper medical 

care and thus would have to be evacuated. Decisions to evacuate were subsequently disseminated via 

word of mouth from floor to floor, since the loss of power also rendered the public address system 

inoperable. 

Tornadoes that strike populated areas leave a number of indicators of their strength in addition to 

damaged and destroyed buildings. Just outside the two SJRMC towers, concrete parking bumpers in the 

parking lot were pulled up from the ground, parking signs were flattened, and cars were thrown into the 

air. In other locations, steel manhole covers and tractor–trailers were tossed around by the storm. 

However, determining the wind speeds required to do such damage is an inexact science. 

41 Lawrence, E. C., Qu, J. Q., and Briskin, E. N. 2011. The Economic Impact of Mercy on the Joplin Area. Available online at 

http://www.mercy.net/sites/default/files/files/joplin–economic–impact1–5714.pdf. 

10 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

Chapter 1
 

0 0.05 0.1 0.15 0.2 0.25

Miles

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 1–6. Aerial photo showing damage to SJRMC and the surrounding area. 

NIST NCSTAR 3, Joplin Tornado Investigation 11 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 1 

A total of 14 lives were lost at SJRMC as a result of the tornado. Due to the significant damage sustained 

by all of the buildings, Mercy, the parent organization of SJRMC, decided to raze the entire facility 

beginning in January 2012. This represented an insured loss estimated at $600 million.42 

Nearly a third of a mile north of SJRMC, close to the northern fringe of the tornado path, wind speeds 

were still strong enough to cause damage. These winds did minor damage to a water treatment plant (Fig. 

1–6), and collapsed an old unreinforced brick masonry building that was used for storage. The Mercy 

Village Apartments building, a wood–framed structure located approximately one–fourth mile south of 

the tornado center and directly east of SJRMC suffered relatively light damage to its envelope and 

structural system. The strong performance of this three–story wood frame building, which was built in 

2003, was likely due to the inclusion of hurricane tie–downs and concrete anchors in its construction. 

These components created a robust and continuous vertical load path for this building. 

This area was also home to the Stained Glass Theater, where Joplin area residents attended live stage 

plays (see Fig. 1–6). There were 56 people in the theater at the time of the tornado.43 Three of these 

occupants lost their lives due to injuries sustained as the tornado struck. According to interviewees, the 

victims did not make it into the basement before the tornado hit. The theater director, who was standing 

at the top of the basement stairs when the building was hit, was injured and died one week later. The 

other two victims died in the theater, due to multiple blunt force trauma to the body. Six other occupants 

were seriously injured; however, it is not known where they were located inside the building when their 

injuries occurred. 

As the tornado left the SJRMC area, it continued to move to the east along 26th Street and took aim at a 

mixed residential and school area that included the Greenbriar Nursing Home, St. Mary’s Catholic 

Elementary School, the Ozark Center for Autism, and Empire District Electric (EDE) substation 59 (Fig. 

1–7). These structures were all directly north of 26th Street, bounded by Jackson Street on the west and 

Main Street to the east. A total of six fatalities occurred in single–family residential structures in this 

area. 

The center of the tornado passed directly over the Greenbriar Nursing Home, and the one–story, wood– 

framed structure was completely demolished, causing 19 fatalities out of a total of 95 occupants. 

Emergency procedures for tornadoes at the nursing home called for the staff to move residents to inner 

hallways and close all doors to residents’ rooms (to avoid flying window glass). All of the injuries that 

led to deaths were due to impact–related causes, except for one individual whose cause of death was 

pneumonia. 

About 300 ft north of the Greenbriar Nursing Home was the Ozark Center for Autism. This facility, a 

three–story concrete building with a two–story steel–framed addition, sustained heavy damage to its 

envelope and interior. Despite remaining structurally intact, the facility was rendered unusable by the 

damage. A little further to the east, the tornado completely demolished the concrete masonry buildings of 

St. Mary’s Catholic Elementary School, Church, and Rectory. None of these facilities were occupied at 

the time. 

42 The Insurance Insider (www.insuranceinsider.com/–1233557/15). 43 Stained Glass Theatre of Joplin (http://www.sgtjoplin.org/id61.html). 

12 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

Chapter 1 

Residential Area

Ozark Center

Greenbriar

St. Marys School

Empire 

Substation #59

26th Street

Main Street

Jackson Street

0 0.05 0.1 0.15 0.2 0.25

Miles

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 1–7. Aerial photo showing locations of the Ozark Center, Greenbriar Nursing
 

Home, St. Mary’s Catholic Elementary School, and EDE substation 59 (from
 

west to east). Residential area is outlined in white.
 

Empire District Electric (EDE) substation 59 was located adjacent to St. Mary’s School and in close 

proximity to the tornado center line. This steel–framed substation, which delivered electrical power to 

residences and businesses in the vicinity, including SJRMC, was completely destroyed. It was one of six 

power substations impacted by the event. The destruction of this substation and the extensive damage to 

other electrical transmission and distribution systems resulted in a loss of power to more than 20,000 EDE 

customers located inside and outside of the tornado–damaged area. The tornado also wreaked havoc on 

water and gas distribution systems. It caused thousands of small leaks in residential and fire water– 

service lines and a subsequent sharp drop in water pressure in the area. Additionally, there was extensive 

damage to gas mains and meters, which resulted in numerous gas leaks in the affected area. 

The tornado then took a sharp turn northeast and moved directly into the heart of another residential area, 

bounded by 20th Street on the north, 32nd Street on the south, Main Street on the west, and Indiana 

Avenue on the east (Fig. 1–8). There were 15 fatalities among the residences in this area, all from 

impact–related causes. 

Just to the northeast of this residential area was a group of school and church buildings, including the 

Franklin Technology Center (a trade school), Joplin High School (the city’s sole public high school), and 

Harmony Heights Baptist Church. Surveillance video from Joplin High School shows that as the tornado 

approached the vicinity of the school, trees and light poles began to collapse near the baseball field, and 

NIST NCSTAR 3, Joplin Tornado Investigation 13 
 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 1 

Figure 1–8. Aerial photo showing the 

locations of a heavily damaged 

residential area, Franklin Technology 

Center, Joplin High School, and 

Harmony Heights Baptist Church. The 

color of each building footprint 

shows the level of damage to that 

structure. 

Damage Key: 

0 0.1 0.2 0.3 0.4 0.5

Miles

Aerial image © 2011 GeoEye. Building 

footprint data Pictometry®. Used with 

permission. Enhancements by NIST. 

Light

St. Marys Elementary 

School

Light Medium Heavy/Totaled Demolished

the air was littered with debris. The tornado reduced Franklin Technology Center to rubble and 

demolished the auditorium and gymnasium buildings (two structures with long–span roofs) at Joplin High 

School, while leaving the other high–school buildings substantially damaged but structurally intact. 

Although no one was inside Joplin High School or Franklin Technology Center at the time of the storm, 

individuals at that time were attending services at the nearby Harmony Heights Baptist Church. By the 

time of the second siren sounding, the attendees had taken shelter, some in the church library and others 

in the children’s nursery. Those in the library laid down on the floor and waited for the tornado to pass. 

Three women died when the storm hit, all from impact–related injuries. One woman was crushed to 

death in the nursery while laying over her son (who survived). Another woman was killed as she stood in 

the doorway of the nursery. The third was fatally injured as she lay on the floor of the library and was 

pelted by debris. 

The tornado then made another right turn and headed due east as it reached 20th Street, a major artery in 

Joplin (see Fig. 1–9). At the intersection of 20th and Connecticut, a number of vehicles with occupants 

14 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

. 

Area

Chapter 1 

were located in the storm’s path. Drivers in this area recalled that rather than witnessing a funnel–shaped 

tornado, the sky suddenly went black and they could see nothing. As the tornado moved closer, the debris 

wall grew thicker and drivers were unable to see the road ahead of them. One mentioned that she realized 

she was in trouble when she saw a car blowing across the street directly in front of her truck. Individuals 

located in vehicles along 20th Street were reportedly pummeled by debris (through broken windows), and 

in some cases, had their cars lifted and thrown by the winds. Two individuals died in their vehicles along 

this stretch of 20th Street, both from impact–related injuries. 

20th St 

Heavily Damaged 

Residential 

Apartments, 

Dillon’s

, 

Vehicles 

Fire Station 

Tornado Center 

.

0 0.1 0.2 0.3 0.4 0.5 

Miles 

S. Range Line Rd 

S. Connecticut Ave 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 1–9. Aerial photo of damaged residential areas (including apartment complexes) 

in Joplin near the intersection of 20th Street and Connecticut. 

A number of apartment complexes were located in this area, including Somerset Apartments, Connecticut 

Pointe Apartments, and Hampshire Terrace. In the Somerset complex, a survivor recalled evacuating her 

apartment and taking refuge underneath the building’s staircase with her neighbors, rather than remaining 

inside her garden–style apartment. Her complex, along with Connecticut Pointe and Hampshire Terrace, 

were significantly damaged in this storm. All 12 of the fatalities that occurred in apartments during the 

tornado happened in these three complexes, and all were from impact–related causes. 

At the southwest corner of 20th Street and Connecticut was the Dillon’s grocery store, where 35 people 

took refuge inside the store’s produce cooler. Even though the building was demolished, everyone inside 

the store survived with only minor cuts, bruises, or scratches. One of Joplin’s fire stations was also in this 

area, to the north of 20th Street. Although this station was located beyond the range of the most extreme 

wind speeds, the station’s garage door was blown open, its roof was lifted off and disconnected from the 

structure, and the fire trucks that were housed inside were damaged. The tornado also affected another 

residential area to the north and south of 20th Street. Six fatalities occurred in homes within this area, 

which is outlined in Fig. 1–9. 

NIST NCSTAR 3, Joplin Tornado Investigation 15 
 

 

 

 

 

 

 

 

 

 

 

Chapter 1 

Continuing eastward, the tornado reached a major intersection at 20th Street and Range Line Road (see 

Fig. 1–10). The commercial district around this location included small stores, restaurants, and large 

chain stores. Businesses in the area included AT&T, Pizza Hut, Macadoodles, Walmart, and Home 

Depot. The center of the tornado passed just to the north of 20th Street between Walmart and Home 

Depot and very near to the Pizza Hut. An industrial district was located on the east side of this area. 

Wal-Mart #59

Home Depot

Macadoodles

AT&T

Pizza Hut

Plaza 

Apartment 

Complex

Industrial Area 20th St. Range Line Rd.

Tornado Center

0 0.05 0.1 0.15 0.2 0.25

Miles

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 1–10. Aerial photo showing damage to a commercial area on the eastern side of
 

Joplin near the intersection of Range Line Road and 20th Street.
 

Media reports stated that 11 people, 5 of whom were employees, were located inside the AT&T store 

during the storm. All of the occupants sought refuge in the men’s bathroom located at the back of the 

44,45 store. One employee remembered the bathroom door coming off its hinges, slamming him in the 

back, and sending him flying into a brick wall.46 Another recalled feeling for a moment like he was flying 

and then the sensation of being crushed, before he was knocked unconscious. By the time the storm was 

over, building materials and other debris had pinned some of the employees, so much so that they were 

unable to move. The building had been completely demolished, and those who could free themselves 

44 McHenry County Blog (http://mchenrycountyblog.com/2011/05/28/joplin–tornado–what–happened–at–the–att–story–across–

from–walmart/). 

45 Communications Workers of America (http://www.cwadistrict7.org/CWA–Newsletters–2011/6–2–CWA–Newsletter–2011.htm). 

46 Ibid. 

16 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 1 

went for help. One death occurred in the store that evening due to impact–related injuries, and the extent 

of survivor injuries there is unknown. 

Similar to circumstances at the Dillon’s store, employees and patrons of the Joplin Pizza Hut sought 

protection in the restaurant’s cooler. As the tornado ripped through the restaurant, it completely 

demolished the structure. Five people died at the Pizza Hut (two employees and three customers). One of 

the employees held the door of the cooler closed with the bungee cord until he was thrown by the storm. 

All of the fatalities resulted from multiple blunt force trauma to the body. 

As the backside of the tornado started to affect this area, the winds shifted to a westerly direction at the 

Home Depot. Strong pressure induced by the tornado’s winds disconnected the store’s roof from its 

concrete tilt–up exterior walls, causing the walls to become unstable. Almost all of the wall panels, 

except for a few around the store’s loading dock, then collapsed, blown outward or inward depending on 

the direction of the winds. According to the Home Depot security manager, approximately 35 of the 

building’s occupants took refuge in the training room located at the back of the store before the storm hit. 

Fortunately, the concrete wall panels adjacent to this refuge area collapsed outward, away from these 

occupants. A total of eight people lost their lives at the Home Depot. Store management reported that 

these individuals had entered the store through the lumber entrance just before the storm hit and were 

walking parallel to the store’s front wall, which collapsed on them. 

Two blocks to the north at the Walmart, strong wind–induced pressure around the southern portion of the 

building disconnected the metal roof system from the perimeter concrete masonry walls, causing the walls 

to become unstable and collapse. The structural damage at Walmart varied significantly from the south 

end to the north end of the building, due to the sharp wind gradient along the length of the building. 

Subjected to much lower wind speeds, the north end of the building sustained much less damage from the 

tornado. 

Before the tornado hit, Walmart employees and patrons were encouraged to congregate at the back of the 

building in the “Site–to–Store” or layaway area, which served as the main refuge area for building 

occupants. While this area provided some protection for the 50 to 60 occupants located there, the area 

was structurally no different than most other areas in the store, and the tornado collapsed the adjacent 

perimeter wall inward and onto this refuge area. Three people lost their lives at Walmart. It is uncertain 

exactly where inside the store these victims were located. However, information from the store’s 

emergency operations center indicated that they were likely close to the center of the store. All three 

fatalities were caused by blunt force trauma to the body. No information could be found on how many 

building occupants did not seek shelter (in the back of the store) or on the number of people injured. 

Approaching Joplin’s eastern city limits, the tornado veered in a southeasterly direction that put yet 

another highly populated residential area, as well as the newly built Joplin East Middle School, at risk 

(see Fig. 1–11). The middle school, built in 2009, was the newest engineered structure surveyed by NIST 

that was affected by the Joplin tornado. The school building included a concrete–walled gymnasium and 

a masonry–walled auditorium, both of which had long–span metal roofs. Surveillance videos facing the 

outside of the school showed that the tornado struck there at about 5:48 p.m. Darkness descended upon 

NIST NCSTAR 3, Joplin Tornado Investigation 17 
 

 

 

 

 

 

Chapter 1 

Reinmiller Rd.

0 0.05 0.1 0.15 0.2 0.25

Miles

Figure 1–11. Aerial photo of damage to a residential area and Joplin East Middle School. 

the area as the winds strengthened. Video footage of the gymnasium, on the south side of the school, 

showed ceiling lights swaying and bits of roofing material, including panels of metal roof decking, falling 

onto the gym floor as the winds began to increase. Later footage showed that failed roof trusses had 

fallen onto the gym floor and the western wall of the gymnasium had collapsed toward the interior of the 

building. 

Similar collapses of the metal roof system and the exterior concrete masonry walls also occurred in the 

auditorium building. Fortunately, on that late Sunday afternoon, the school was not occupied at the time 

of the collapse. 

The area outlined in white in Fig. 1–11 was the last of the heavily populated residential districts in Joplin 

to be damaged. Three people were killed there in detached homes and another person died in a vehicle. 

In a number of the residential structures that were heavily damaged in Joplin that day, the tornado broke 

apart the building’s structural elements (i.e., roof, walls, and foundation). The tornado followed a 

southeasterly path and began weakening considerably as it left the Joplin area. The now smaller tornado 

continued through the City of Duquesne, crossed Interstate 44 near its junction with Highway 249. It then 

traveled another 12 miles through a sparsely populated rural area before ending about 5 miles north 

northeast of Granby, Missouri, for a total tornado track length of 22.1 miles (6 miles within the City of 

Joplin). 

18 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 1 

1.3 THE TOLL 

In its wake, the May 22, 2011, Joplin tornado left 161 fatalities and more than 1,000 injuries. This EF–5 

rated tornado was on the ground for approximately 6 miles and 15 min in Joplin, Missouri, and created a 

damage path as much as a mile wide. The tornado was the deadliest single tornado in the United States 

since the official NWS records began in 1950. 

Of the 161 deaths, a total of 155 (or 96 percent) were due to impact–related injuries (generally identified 

as “multiple blunt force trauma to body” on the death certificates). Of these impact–related fatalities, 135 

(or 87 percent) occurred inside buildings that were significantly damaged, and over half (58 percent) 

occurred in residential buildings, including the Greenbriar Nursing Home. Some contributing factors to 

these fatalities included the following: (1) the wind and wind–borne debris environment to which 

occupied buildings were exposed, (2) individuals’ delay in seeking “safer” or indoor protection, and (3) 

individuals’ age. First, all indoor, impact–related fatalities in Joplin occurred in buildings experiencing 

wind speeds estimated as EF–3 or higher, except for the two deaths that occurred in the Meadows 

Healthcare facility (which experienced wind speeds estimated as EF–1) and the six deaths that occurred 

within five single–family homes. Second, individuals’ delay in responding to the threat was due to a lack 

of awareness of the tornado or an inability to perceive personal risk associated with the tornado 

emergency. Third, a disproportionately higher number of people aged 60 years or older died or were 

injured as a result of this tornado, when calculating death rates (or the number of deaths within a certain 

age range per thousand people in that age range within the tornado’s damage path). 

The damage to the built environment made this the costliest tornado on record, with losses approaching 

$3 billion. The Joplin tornado damaged 553 business structures and nearly 7,500 residential structures; 

over 3,000 of those residences were heavily damaged or completely destroyed. Unlike many earlier 

tornadoes, which typically affected less populated or developed areas, the Joplin tornado affected a 

densely populated region that encompassed residential areas, a number of schools, large commercial 

facilities, and critical facilities. In addition, this tornado significantly damaged lifeline systems in the 

affected areas, including the regional electric power transmission and distribution infrastructure, 

numerous water and fire service lines and gas mains, and thousands of utility connections and meters. 

Also contributing to these losses was an estimated 3 million cubic yards of debris (enough to fill a 

football field 120 stories high). Wind–borne debris exacerbated the damage to the built environment and 

contributed to some of the 155 impact–related fatalities. The accumulation of debris also complicated the 

restoration of lifeline services as it impeded access by utility workers in the days following the tornado. 

1.4 NIST’S JOPLIN TORNADO INVESTIGATION 

Given the magnitude and consequences of this tornado, the National Institute of Standards and 

Technology (NIST) sent four engineers to Missouri on May 24–28, 2011, to conduct a preliminary 

reconnaissance.47 Based on subsequent analyses of the data they collected and other criteria required by 

law and regulation, NIST Director, Patrick Gallagher, established a Team under the National Construction 

Safety Team (NCST) Act on June 29, 2011, to proceed with a more comprehensive study of the disaster. 

The establishment of this Team was announced in the Federal Register on July 19, 2011 (76 FR 42683). 

47	 See http://www.nist.gov/el/disasterstudies/upload/Joplin_Reconnaissance_Presentation061511–2.pdf for more information about 

NIST’s preliminary reconnaissance in Joplin. 

NIST NCSTAR 3, Joplin Tornado Investigation 19 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 1 

Additional information regarding the rationale for the technical investigation is provided in the 

investigation plan.48 

The public was kept informed on the investigation through publications and briefings (available through 

NIST Disaster and Failure Studies Program web site at http://www.nist.gov/el/disasterstudies). 49 50 Publications included the investigation plan (May 2012), progress report (November 2012), and draft 

final report for public comment51 (November 2013). Briefings were provided to the NCST Advisory 

committee on October 7, 2011, December 10, 2012, and December 10, 2013. These briefings were held 

in Gaithersburg, MD and were open to the public. The briefing presentation slides were made available 

online.52 

The draft final report for public comment was released on November 21, 2013, in Joplin, MO. A briefing 

was provided first to local officials, followed by a news briefing53 that was streamed live over the internet. 

A 45-day public comment period followed the release of the report, with a closing date of January 6, 

54 55 2014. All public comments were considered in preparation of this final report.

Data and information collected during the course of the investigation will be available through the NIST 

Disaster and Failure Studies Event Data Repository web site56 when the Joplin Tornado Repository is 

completed. 

NIST is a non–regulatory agency of the U.S. Department of Commerce. NIST technical investigations 

are focused on fact finding, not fault finding. No part of any report resulting from a NIST investigation 

into a structural failure or from an investigation under the NCST Act may be used in any suit or action for 

damages arising out of any matter mentioned in the report (15 U.S.C. 281a, as amended by Public Law 

107–231). 

1.4.1 Goals 

NIST’s investigation of the Joplin tornado had two major goals. The first was to investigate the wind 

environment and technical conditions that caused fatalities and injuries; the performance of emergency 

communications systems and the public response to such communications; and the performance of 

48 NIST Special Publication 1132, “Investigation Plan – National Institute of Standards and Technology (NIST) Technical 

Investigation of the Joplin, Missouri, Tornado of May 22, 2011,” available at http://dx.doi.org/10.6028/NIST.SP.1132. 

49 Ibid. 

50 NIST Special Publication 1139, “Progress Report National Institute of Standards and Technology (NIST); Technical Investigation 

of the May 22, 2011, Tornado in Joplin, Missouri,” available at http://dx.doi.org/10.6028/NIST.SP.1139. 

51 NIST NCSTAR 3 (Draft for Public Comments), “Draft Final Report, National Institute of Standards and Technology (NIST)

Technical Investigation of the May 22, 2011, Tornado in Joplin, Missouri,” available at

http://nvlpubs.nist.gov/nistpubs/NCSTAR/NIST.NCSTAR.3.pdf. 

52 Information on the NCST Advisory Committee meetings, including copies of the presentations, is available at 

http://www.nist.gov/el/disasterstudies/ncst/index.cfm. 

53 http://www.nist.gov/el/disasterstudies/joplin-112113.cfm. 

54 All public comments received are available at http://www.nist.gov/el/disasterstudies/weather/joplin_tornado_2011.cfm. 

55 Four public comments made reference to the U.S. National Grid, which was not used in this report. The use of the U.S. National 

Grid will be considered in future NIST Disaster and Failure Studies. 

56 http://www.nist.gov/el/disasterstudies/repository_home.cfm 

20 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 1 

57	 58 residential, commercial, and critical buildings, designated safe areas in buildings, and lifelines. The 

second goal was to develop findings and recommendations that can serve as the basis for: 

	 Potential improvements to requirements for the design and construction of buildings, 

designated safe areas, and lifeline facilities in tornado–prone regions; 

	 Potential improvements to guidance for tornado warning systems and emergency response 

procedures; 

	 Potential revisions to building, fire, and emergency communications codes, standards, and 

practices; and 

	 Potential improvements to public safety. 

1.4.2 Objectives 

The primary objectives of the NIST technical investigation of the Joplin tornado were to: 

1.	 Determine the tornado hazard characteristics and associated wind fields in the context of 

historical data; 

2.	 Determine the response of residential, commercial, and critical buildings, including the 

performance of designated safe areas; 

3.	 Determine the performance of lifelines as it relates to the continuity of operations of 

residential, commercial, and critical buildings; 

4.	 Determine the pattern, location, and cause of fatalities and injuries, and associated 

performance of emergency communications systems and public response; and 

5.	 Identify, as specifically as possible, aspects of current building, fire, and emergency 

communications codes, standards, and practices that warrant revision. 

The technical investigation in support of these objectives spanned over 2 years. The objectives are 

addressed in this report in a chapter format. Chapter 2 supports objective 1 (determining tornado hazard 

characteristics and associated wind fields in the context of historical data). Chapter 3 supports objectives 

2 and 3 (determining the response of residential, commercial, and critical facilities and the performance of 

lifelines as they relate to these facilities). Chapter 4 supports objective 4 (determining the pattern, 

location, and reported cause of fatalities and injuries, and associated emergency communications and 

public response). Finally, objective 5 (identifying aspects of codes, standards, and practices that warrant 

revision) is supported by all of the chapters in this report, and the investigation’s findings and 

recommendations are summarized in Chapter 5. 

57 For example, hospitals, fire stations, police stations.
 

58 Lifelines considered in this investigation were electrical power, natural gas, and water supply infrastructure and facilities.
 

NIST NCSTAR 3, Joplin Tornado Investigation 21 
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22 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

TORNADO HAZARD CHARACTERISTICS 

2.1 INTRODUCTION 

Chapter 2 discusses the hazard characteristics and associated wind fields in the May 22, 2011, Joplin 

tornado and this storm’s historical context on local, regional, and national levels. Section 2.2 outlines the 

meteorological conditions immediately before and at the time of the tornado occurrence. Section 2.3 

estimates the near–surface wind field of the Joplin tornado through both direct and indirect measurement 

techniques. In Sec. 2.4, the U.S. tornado hazard is discussed in detail with respect to tornado climatology 

and tornado–related losses including comparisons to the Joplin tornado. Section 2.5 assesses the EF 

Scale, the guidance for its application, and its implementation in the Joplin tornado and other significant 

tornado events. 

2.2 METEOROLOGICAL CONDITIONS 

2.2.1 Objective 

Section 2.2 documents the meteorological/environmental conditions and the associated timeline of key 

events leading up to and during the Joplin tornado. It establishes the general factors leading to the 

development of the Joplin tornado, and serves as a baseline for understanding the Joplin tornado in a 

historical context. The discussion is largely based on watches, warnings, and meteorological information 

on the Joplin tornado provided by the NWS and siren information provided by the City of Joplin. 

2.2.2 Joplin Environment and Timeline 

Based on surface– and upper–air observations, the potential for severe weather in the Joplin area on May 

22, 2011, was fairly evident. The upper levels of the atmosphere included low pressure, denoted in Fig. 

2–1 by an “L” centered over the Dakotas. As air flows around low pressure in a counterclockwise 

direction in the northern hemisphere, the atmosphere above Joplin (red star) was experiencing 

southwesterly winds. Wind speed and direction in Fig. 2–1 are denoted by the “wind barbs” shown in 

blue; the nearest wind barb to Joplin is circled. The wind barbs point in the direction from which the 

wind is coming (from the southwest for the circled barb). Each long barb represents 10 knots,59 each 

short barb, 5 knots, and each pennant, 50 knots. In the case of the circled barb near Joplin, the wind speed 

shown is 40 knots from the southwest (at a height of approximately 5,800 meters or 19,000 feet). 

Surface analysis (Fig. 2–2) shows a warm front (red scalloped line) just west of Joplin (red star) near the 

time of the breakout of storms. A surface low (denoted by “L”) was just to the west of Joplin in extreme 

southeastern Kansas, with a dryline (orange scalloped line) extending southwest from the center of the 

low. These conditions can provide a focus for low–level moisture convergence that often initiate and 

sustain strong storms provided other severe weather parameters are in place (Church 1993). 

59 1 knot = 1.15 mph = 0.514 m/s. 

NIST NCSTAR 3, Joplin Tornado Investigation 23 
 

 

 

 

 

 

Chapter 2 

Source: NOAA. Enhancements by NIST. 

Figure 2–1. 500 millibar (mb) analysis at 7 a.m. CDT (1200 Coordinated Universal Time 

(UTC)) on May 22, 2011. 

Source: NOAA. Enhancements by NIST. 

Figure 2–2. Surface analysis at 7 p.m. CDT (0000 UTC, May 23, 2011) on May 22, 2011. 

24 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

A balloon sounding (plot not shown) from the Springfield, MO NWS forecast office, 100 km (60 mi) to 

the east of Joplin, was launched at 7 PM CDT (00 UTC). From this sounding a calculated environmental 

convective available potential energy (CAPE) of nearly 4,000 joules per kilogram (J/kg) was made. 

CAPE is a vertically integrated measure of buoyancy, i.e., any positive CAPE indicates a potential for 

convective clouds to form. Tornadic storms, however, also require a certain amount of low-level wind 

shear (e.g., the vector difference of the wind at 5,000 ft altitude minus the surface wind vector) to create 

the rotation necessary to form tornadoes. The balloon sounding indicated low-level shear of around 25 

m/s (50 mph), more than adequate to support severe thunderstorms and tornadogenesis given the large 

amount of instability (CAPE). 

Figure 2–3 shows a plot of CAPE versus wind shear values in Joplin compared with historical severe 

thunderstorm environments. The red line in Fig. 2–3 denotes a separation of “significant severe” 

environments from “non–significant severe” environments. Significant severe is defined in Brooks 

(2003b) as “having hail at least 5 cm in diameter, wind gusts at least 120 km/hr, or a tornado of at least F2 

damage”. Based on the conditions, the Joplin environment was favorable for the production of severe 

thunderstorms, including tornadoes. 

Source: Brooks et al. (2003b). Enhancements by NIST. 

Figure 2–3. Wind shear and CAPE for severe thunderstorm environments. "Best 

Discriminator" line denotes areas to right and above as being more favorable for 

significant severe thunderstorms. 

NIST NCSTAR 3, Joplin Tornado Investigation 25 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

The severe weather environment described above was anticipated by the NOAA/NWS SPC. The tornado 

outlook issued at 1 a.m. CDT (0600 UTC) on May 22, 2011 included a “10 percent probability of strong 

tornadoes (EF–2 or greater) within 25 miles of a point” (Fig. 2–4) in the Joplin area. Also, throughout the 

day on May 22, the SPC issued three separate “Mesoscale Convective Discussions” for areas that 

included Joplin up to and including the time of the tornado. These Mesoscale Convective Discussions 

clearly pointed to an environment in the Joplin area that was favorable for the development of a 

significant severe weather event. Text from and links to the Mesoscale Convective Discussions are 

provided in Appendix A. 

Source: NOAA. 

Figure 2–4. Tornado outlook issued by NOAA’s Storm Prediction Center at 1 a.m. CDT 

(0600 UTC) on May 22, 2011. 

At 1:30 p.m. CDT (1830 UTC), about 4 hours before the tornado struck Joplin, the SPC issued a tornado 

watch for a large portion of northwest Arkansas, southeast Kansas, eastern Oklahoma, and southwest and 

central Missouri (see Appendix A, Sec. A.2). Thunderstorms did develop in the Joplin area beginning 

between 4 and 5 p.m. (2100 and 2200 UTC). 

In response to these storms, a series of tornado warnings for the Joplin area were issued by the NWS 

Forecast Office in Springfield, Missouri. The areas covered by these warnings are shown in Fig. 2–5. 

The May 22, 2011 timeline of tornado watches and warnings is shown in Fig. 2–6. Tornado Warning 

(TO.W) Polygon 30 was issued by the Springfield NWS office (Fig. 2–5) at 5:09 p.m. (2209 UTC), which 

included the northeast portion of Joplin. The first citywide warning siren in Joplin was sounded at 5:11 

p.m. CDT (2211 UTC). The siren timeline is also illustrated in Fig. 2–6. For details on how people 

responded to and interpreted the warnings and sirens in Joplin, please consult Chapter 4. 

26 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

Tornado watch 

issued by SPC 

Chapter 2 

Source: NWS (2011). 

Figure 2–5. Tornado warnings issued by the Springfield NWS office on May 22, 2011. 

Zulu time, or Z, in the figure is the same as UTC time (Z = UTC). Estimated NWS track of 

the Joplin tornado shown outlined in brown. 

Tornado affects 

Joplin East 

Middle School 

Tornado 

affects 

Joplin 

High 

School 

Second 3-minute 

siren sounded as 

tornado enters the 

City of Joplin 

Initial tornado 

touchdown 

(Spotter reports) 

Second tornado 

warning issued 

(TO.W 31) 

Initial 3-minute 

siren sounded 

First tornado 

warning issued 

(TO.W 30) 

Moderate risk of 

severe storms issued 

by SPC 

5:50 

5:30 

5:10 

4:00

3:00

2:00

5:205:40 

1:30 pm 

3:00 pm 

5:09 pm 

5:11 pm 

5:17 pm 5:34 pm 

5:38 pm 

5:42 pm 

5:48 pm 

May 22, 2011 

Watches and warnings timeline 

Tornado timeline 

Siren timeline 

Figure 2–6. Timeline of watches, warnings, sirens, and the tornado itself. 

NIST NCSTAR 3, Joplin Tornado Investigation 27 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

A storm separate from the one that prompted TO. W 30 developed and a second tornado warning 

polygon60 was issued by the Springfield office at 5:17 p.m. (2217 UTC) that included the entire city of 

Joplin (TO.W 31 in Fig. 2–5). Figure 2–7 shows radar images from 5:24 p.m. (2224 UTC) to 5:53 p.m. 

(2253 UTC). The issuance of TO. W 31 in Fig. 2–5 was based on the storm identified from radar in Fig. 

2–7. The initial tornado touchdown, based on spotter reports, was at 5:34 p.m. (2234 UTC) southwest of 

the Joplin city limits. The tornado timeline is also illustrated in Fig. 2–6. The citywide warning sirens 

sounded again in Joplin at 5:38 p.m. (2258 UTC). Surveillance camera footage provided by Joplin City 

Schools indicated that the tornado struck Joplin High School at approximately 5:42 p.m. (2242 UTC) and 

Joplin East Middle School at approximately 5:48 p.m. (2248 UTC). The Springfield NWS office issued 

another warning polygon (TO.W 32) at 5:48 p.m. (2248 UTC) to extend the tornado warned area to the 

east of Joplin. The track of the Joplin tornado in comparison to the areas covered by the tornado warnings 

is shown in Fig. 2–5, and an estimated center of the tornado track based on the work in Sec. 2–3 is 

illustrated in Fig. 2–8. 

The issuance of TO.W 30 and the sounding of the first sirens in Joplin occurred 25 and 23 minutes 

respectively before the first reported tornado touchdown at 5:34 p.m. (2234 UTC). However, the storm 

that prompted TO. W 30 did not produce a tornado and the warning only included a small portion of the 

city of Joplin. 

The issuance of TO. W 31, which included the entire city of Joplin, occurred 17 minutes before (i.e., lead 

time of 17 minutes) the first tornado touchdown. The storm that prompted TO. W 31 went on to produce 

the tornado that affected the city of Joplin. The national average for tornado lead times was 15 minutes 

based on fiscal year (FY) 2011 data, and since the advent of the NWS NEXRAD (Next Generation Radar 

System) radars throughout the United States in the early to mid 1990’s, lead time has been approximately 

12 minutes on average.61 

It should be noted that Joplin was not in close proximity to NWS radars. Both the KINX (Tulsa) and 

KSGF (Springfield) radars were a considerable distance (approximately 100 kilometers or 60 miles) away 

from the storm. Even at the lowest beam elevation angle, 0.5 degrees, the information available at such 

distances relates to conditions at altitudes (approximately 1.5 kilometers or 0.93 miles above ground) that 

are orders of magnitude greater than what would be relevant to damage caused near the ground surface (in 

most cases under 20 meters or 66 feet). In addition, the NWS Service Assessment concerning the Joplin 

tornado found that “...low–level rotational intensification and the subsequent tornado occurred rapidly 

and that more continuous near–surface radar sampling and information were needed”. Given the lack of 

detailed wind information available from the NWS radars, NIST used indirect methods to estimate the 

wind speeds experienced in Joplin during this event. 

60	 See NOAA (http://www.srh.noaa.gov/images/bmx/aware/swaw_2010/web_version_pages_p6.pdf) for general description of 

warning polygons. 

61 NOAA (http://www.osec.doc.gov/bmi/budget/11BiB/NOAA%20Performance.pdf) 

28 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

Chapter 2 

Hook Echo 

Source: NOAA. Enhancements by NIST. 

Figure 2–7. Radar reflectivity sequence from the Springfield radar. Radar reflectivity is 

the right panel and radial velocity is the left panel of each image. For radial velocity, red 

to yellow colors indicate winds receding from the radar (which is located to the east of 

Joplin), green to white colors indicate winds approaching the radar. These colors in 

close proximity suggest rotation and signify the approximate tornado position. A "hook 

echo" is seen in reflectivity images, also a possible indication of a tornado. These 

features are annotated in the 2248 UTC panel. 

NIST NCSTAR 3, Joplin Tornado Investigation 29 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

Aerial image © 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 2–8. Center of Joplin tornado track as estimated by NIST. 

2.3 NEAR–SURFACE WIND ENVIRONMENT 

2.3.1 Objective 

Given the lack of near–surface wind information provided by radar (Sec. 2.2) and of direct measurements 

of wind speeds (Sec 2.3.3) in the most heavily damaged areas in the Joplin tornado, indirect techniques 

were used to estimate the near–surface wind field. Two independent techniques were used: inference of 

wind speeds from observed damage using the EF Scale, and modeling of the wind field using a Rankine 

vortex model fitted to observed tree fall data. These estimates of the near–surface wind field are 

important for understanding the performance of buildings and structures as well as understanding this 

event in the context of tornado climatology and probabilistic hazard assessments. The wind speed 

estimates generated from these techniques are evaluated in relation to similar analyses reported in the 

technical literature. Section 2.3.2 discusses the general structure of a tornado wind field, Sec. 2.3.3 

discusses direct wind speed measurements from the Joplin area on the day of the tornado, and Sec. 2.3.4 

details the methods and analysis used for indirect wind speed estimation. 

2.3.2 Tornado Wind–Field Regions 

In general, the air flow regions in and around an idealized tornado can be thought of as the five separate 

regions illustrated in Fig. 2–9. Region Ia is termed the outer flow. This spiraling outer flow typically 

extends outward from the core (Region Ib) at least 1 km (Davies–Jones et al. 2001) and consists of air 

that approaches and rises around the core. The core, or Region Ib, surrounds the central axis of the 

tornado and extends outward to the radius of maximum tangential winds. The radius of the core region is 

typically tens to hundreds of meters (Davies–Jones et al. 2001). 

Due to the stability of the core, there is limited entrainment of air into the core from Region Ia. 

Therefore, the core consists for the most part of air that has entered through the boundary layer (Region 

II) and corner region (Region III) or the upper region (Region IV). The boundary layer, Region II, 

consists of an inflow that is influenced by frictional interaction with the earth’s surface. Due to this 

interaction, the flow in the boundary layer tends to have a more radial (towards the tornado center) flow 

compared to the outer flow. The depth of the boundary layer is typically from 10 m to 100 m (Markowski 

and Richardson 2010). The effects of friction near the surface can actually increase tornado wind speeds 

in the boundary layer (Kosiba and Wurman 2010; Davies–Jones et al. 2001) and/or the corner flow region 

(Church 1993). Air that enters the tornado core from the boundary layer must first pass through the 

30 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

© 2004 Frank Lombardo. Used with permission. Enhancements by NIST. 

Figure 2–9. General tornado flow regions. 

corner region (Region III). This is a highly complex region where the flow must transition from a 

horizontal flow along the surface to a vertically upward flow, or “turn the corner,” in the presence of a 

tornadic vortex. Most heavily damaged areas in tornadoes have likely come in contact with corner flow 

and a large amount of wind–borne missiles and debris are generated in this region (Davies–Jones et al. 

2001). Region IV, the upper flow of the tornado consists of the rotating updraft, or mesocyclone, of the 

parent thunderstorm. 

In general, the tangential velocity of the wind field, not including tornado translation (i.e., movement) or 

vertical wind speed, as it extends radially from the center of the tornado, can be described and estimated 

using a Rankine vortex model (ANS 2011). Although other vortex models exist (Wood and Brown 

2011), the Rankine model has been used in a number of engineering applications (ANS 2011). The 

Rankine vortex is an idealized, axisymmetric vortex model, sometimes called a Rankine combined vortex. 

The wind speed at radius r, which is denoted as ቙ዷዽሆቛቯቜ, displays an increase from the center of the 

tornado outward to the radius of maximum wind (RMW) and a hyperbolic decay thereafter based on the 

decay exponent (ሏ). An illustration of a normalized Rankine vortex is shown in Fig. 2–10, and the 

mathematical description is shown in Eq. 2.1. 

ሾ ሆ ቙ዷዽሆቛቯቜ ቭ ቙ሁድሌ ቡ

ዬዧዱቁ ሂ ቯ ቲ ቕቐቚ (2.1) 

ሾ ዬዧዱ ቙ዷዽሆቛቯቜ ቭ ቙ ቁ ሁድሌ ቡ ሂ ቯ ቱ ቕቐቚ ሆ

The maximum velocity at the RMW generated by the tornadic vortex (Vmax), especially near the surface 

(Davies–Jones et al. 2001) can have both a radial (Vr, toward the center of the tornado) and tangential 

(Vθ) wind component, as shown in Fig. 2–11. The Rankine vortex model can be used to explain both 

components (Potvin et al. 2009). 

The translation speed (VT) is defined as the speed of the tornado movement. The translation speed 

represents movement of the tornado in the translation direction (ሁዮ) and is used to estimate a translation 

velocity. This velocity is additive to the velocity estimated from the Rankine model. In other words, the 

NIST NCSTAR 3, Joplin Tornado Investigation 31 
 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

Figure 2–10. Normalized Rankine vortex showing maximum wind speed at RMW 

(ዱ ቭ ዻህ ዺቜ. 

total velocity at any point in the tornado wind field is equal to the vector sum of the translation, radial, 

and tangential velocities (Fig. 2–11). 

With the information described above, an estimate of the resultant wind speed, V, and associated wind 

direction, β, can be made. The wind direction (β) is measured clockwise with zero degrees being from 

true north. The coordinates and sign convention are illustrated in Fig. 2–11, and will also be used in 

modeling of the Joplin tornado wind field 

(Sec. 2.3.4). 

Figure 2–11. Generalized wind 

vector for a point denoted by the 

small gray circle. RMW is distance 

from gray circle to “tornado 

center.” 

32 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

2.3.3 Direct Wind Speed Observations 

2.3.3.1 Wind Environment 

The Joplin Airport Automated Surface Observing System (ASOS) station (call letters KJLN) was located 

5 miles to 6 miles north of the tornado as the storm passed through Joplin, well outside of the damaged 

area. However, even at this distance, measurements from KJLN suggest that the wind speeds at this 

location may have been affected by the mesocyclone of the parent thunderstorm (Region IV) for 

approximately 15 minutes, from 5:34 p.m. CDT to 5:49 p.m. CDT (2234 to 2249 UTC). This time period 

is “boxed” in Fig. 2–12, which shows the time histories of wind speed and direction recorded by the 

KJLN anemometer at a height of 10 m above the ground. The environment appears to begin being 

affected around the approximate time of the tornado touchdown at 5:34 p.m. CDT (2234 UTC). The time 

of touchdown is shown as the left edge of the black box in Fig. 2–12. The wind speed increases to a 

maximum 2 minute average value reaching 20.0 m/s (44.7 mph), and a maximum gust wind speed (3– 

second gust) over 24.0 m/s (53.7 mph). The wind direction backs (turns counterclockwise) from 

approximately 160 degrees (from the south–southeast) around 5 p.m. CDT (2200 UTC) to about 345 

degrees to 360 degrees (from due north to north–northwest) during the time when the tornado was on the 

ground. This wind direction is coincident with inflow toward the positions of the mesocyclone and the 

tornado relative to KJLN at these times. 

0

5

10

15

20

25

Wind Speed (m/s)

Time (CDT)

5:00 PM 5:15 PM 5:30 PM 5:45 PM 6:00 PM

Wind Direction (deg)

0

60

120

180

240

300

360

3-second Wind Gust

2-minute Wind Speed

Wind Direction

Data Source: NOAA. Analysis by NIST. 

Figure 2–12. Time history of mean and gust wind speed and mean wind direction from 

the Joplin ASOS station (KJLN) from 5 p.m. to 6 p.m. CDT (2200–2300 UTC), on May 22, 

2011. Boxed area is approximate time when the tornado was on the ground in Joplin. 

NIST NCSTAR 3, Joplin Tornado Investigation 33 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

The ASOS station at the Joplin Airport was the only identified “direct” wind measurement near the Joplin 

tornado. However the anemometer did not sample tornadic wind speeds and was well outside the 

damaged area. Also, as discussed earlier, no information could be gained from the NWS radars about 

wind speeds close to the surface. The lack and subsequent need of accurate, rugged near–surface (< 20 

meters or 66 feet) wind speed measurements in tornadoes has been noted in the literature for over 20 

years (NRC, 1993). Therefore, methods of indirect wind speed estimation in the tornadic environment 

were used as described in the following section. 

2.3.4 Indirect Wind Speed Estimation 

2.3.4.1 Observed Damage (EF Scale) 

EF–Scale Process—

The Enhanced Fujita (EF) Scale is used to estimate and then rate the intensity of the maximum wind 

speeds in a tornado based on observed damage. The scale ranges from EF–0 to EF–5, with EF–5 being 

the most intense. The EF–Scale process involves observing damage to a specific element of the 

environment, called a damage indicator (DI). The scale has 28 DIs, ranging from small outbuildings, 

one– or two–family residences, schools, and shopping malls to electrical transmission lines and softwood 

and hardwood trees. Corresponding to each of the 28 DIs are several degrees of damage, or DODs. The 

full list of DIs and corresponding DODs is available (Texas Tech University, 2006). DODs range from 

the initiation of damage to complete destruction (i.e., a progressive wind damage sequence). There is a 

range of wind speeds associated with each DOD. Each range includes an expected wind speed associated 

with ‘normal’ conditions, as well as lower and upper bounds to account for different conditions (i.e., 

weaker or stronger wind resistance than typical construction, respectively). These wind speed values 

were developed by wind engineers and meteorologists who were considered experts in the field of 

tornadoes. Once a wind speed value is chosen for a particular DI and DOD, an EF–Scale number is 

assigned based on Table 2–1. Additional information on the EF Scale and its predecessor, the Fujita 

Scale (F Scale), is provided in Sec. 2.5. It should be noted that the EF Scale implicitly represents a lower 

bound estimate to the wind speed values that cause damage. For example if a transmission line is 

expected to fail at 49 m/s (110 mph) and a transmission line failure is observed in the field, it is possible 

that the actual wind speeds were > 49 m/s (110 mph). The transmission line with an expected failure wind 

speed of 49 m/s (110 mph) can provide no additional information on the wind speeds that may have 

occurred. This issue is most apparent when attempting to rate strong tornadoes in the EF Scale. For 

example, in the EF Scale document, there are currently only five (5) DI’s where an expected value of 

wind speed would give an EF–5 rating (greater than 89 m/s or 200 mph). 

Selected NIST–Surveyed Structures and Comparisons with Other Studies—

Damage to selected engineered structures surveyed by NIST following the tornado was analyzed using 

the EF–Scale rating process. The damage to these structures is described in detail in Chapter 3. They 

were assigned an EF number for the purposes of this report using ground survey data and aerial 

photographs. These EF numbers were compared with those developed by other researchers and 

practitioners who surveyed the same structures after the Joplin tornado. In some cases, a single large 

building had levels of damage that varied significantly across the length of the structure. Current EF 

Scale guidance does not address how to rate large buildings with varying DOD. 

34 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

Table 2–1. Enhanced Fujita Scale. 

EF Number Wind Speed (mph) Wind Speed (m/s) 

0 65–85 29–38

1 86–110 38–49

2 111–135 50–60

3 136–165 61–73

4 166–200 74–89

5 200+ 89+

One example that demonstrates the challenges in assigning definitive DODs for large structures involves 

the Walmart (Store #59) located at 1501 South Range Line Road in Joplin. This large building was 573 

feet (175 meters) long, oriented along a north–south axis. The building was located north of the center 

line of the tornado track. The southern part of the building, which was closer to the center of the tornado, 

suffered extensive damage, while the northern part of the building experienced much less damage as 

shown by the aerial photo in Fig. 2–13. 

Figure 2–13. Aerial photo of Walmart Store 

#59 showing extensive damage to the 

southern (bottom) half of the building. 

© 2011 GeoEye. Used with permission. 

Enhancements by NIST. 

NIST NCSTAR 3, Joplin Tornado Investigation 35 
 

 

 

 

 

 

 

 

 

 

Chapter 2 

Under the EF scale guidance, this type of building is classified as DI 12, a “Large, Isolated Retail 

Building.” However, which DOD should be selected is less than clear. The structure could fall into 

either DOD 6, “inward or outward collapse of exterior walls,” which occurred in the southern half of the 

building, or DOD 7, “complete destruction of all or large sections of the building,” which could apply 

based on Fig. 2–13. However a ground level picture (Fig. 2–14), reveals that some of the southern 

portion of the structure remained in place and suggests a DOD less than 7. The expected wind speeds 

(and lower/upper bounds) for DOD 6 and DOD 7 for DI 12 are 118 mph (98/158) and 147 mph 

(110/201), respectively. Consequently, assigning a specific DOD and an associated wind speed becomes 

somewhat subjective. Since the damage to the Walmart clearly exceeded DOD 6 and didn’t quite meet 

DOD 7 for a portion of the building, a point estimate of 140 mph +/– 15 mph was assigned. This made 

the estimated lower bound 125 mph, a value that could still account for DOD 6 while falling within the 

bounds of DOD 7. The upper bound, 155 mph, still falls within the range of DOD 6 wind speeds, and sits 

squarely within the wind speed range associated with DOD 7. 

Figure 2–14. Elevation view of southwest–facing wall of Walmart Store #59. 

Table 2–2 shows the wind speeds and associated EF numbers estimated by NIST using the EF Scale at 

the Walmart and the locations of several other NIST–surveyed buildings. NIST’s estimates were 

compared with those of other researchers and practitioners who also used the EF Scale (FEMA 2012; 

Prevatt et al. 2012; Marshall 2012; and Karstens et al. 2012), as shown in Table 2–2, and with estimates 

by Coulbourne and Miller (2012), which were back–calculated from observed failures of specific building 

components or systems. 

Although the DIs used in the estimates were the same among all surveyors, there were considerable 

variations in the estimated DODs, estimated wind speeds, and final EF–Scale ratings. The varying 

estimates of damage and wind speed suggest that there is ambiguity and subjectivity in the current version 

of the EF Scale and its application, even among experienced researchers and practitioners. 

Residential Construction—

Based on a database created by Pictometry International Corporation (used with permission), NIST 

determined there were approximately 7,400 residential structures estimated to have been damaged due to 

the Joplin tornado. The database separated damage levels into four classes (light, medium, heavy/totaled, 

36 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

Table 2–2. Estimated wind speeds for NIST–surveyed structures using EF Scale. 

NIST–Surveyed 

Structure 

Damage Indicator 

(DI)* 

Degree of 

Damage (DOD)** 

Estimated Wind 

Speed (mph) Estimated EF Number 

NIST Other NIST Other NIST Other NIST Other 

Walmart 12 12a,d 6–7 6a, 7d 140 ± 15 173d 3 4a,d 

Home Depot 12 12a 6–7 7a 150 ± 15 N/A 3 4

a 

Franklin Technology 

Center 

15 15d 9 9d 150 ± 15 153d, 143e 3 3

d,e 

SJRMC (East/West 

Towers) 

20 20a,c 7 10a,c 140 ± 15 148c 3 3a,c 

Joplin East Middle 

School 

16 16d 8 7d 140 ± 15 125d , (137–

164)

b 

3 2

a,d, 3b 

Joplin High School 16 16a,d 8–9 11a, 9d 140 ± 15 120b, 139d , 

158e 

3 2

b

, 3a,d,e 

*DI numbers: 12, large, isolated retail building; 15, elementary school (the Franklin Technology Center was not an
 

elementary school but was a building of similar construction); 16, junior or senior high school; 20, institutional building.
 

**DOD numbers: see Texas Tech University 2006 (Available online at
 

http://www.depts.ttu.edu/nwi/Pubs/FScale/EFScale.pdf)
 

a. FEMA 2012. 

b. Coulbourne and Miller 2012. (Estimated wind speed values back–calculated from ) 

c. Prevatt et al. 2012. 

d. Marshall 2012. 

e. Karstens et al. 2012.
 

Key: SJRMC, St. John’s Regional Medical Center.
 

demolished). These damage classes were estimated by analyzing the differences between pre– and post– 

storm aerial imagery (orthorectified and oblique) of the Joplin area.62 The damage classes estimated for 

building footprints in part of Joplin are shown in Fig. 2–15. The numbers of structures assigned to each 

class citywide are listed in the last row of Table 2–3. Wind speed statistics and numbers of structures 

estimated for residential damage levels using EF Scale. 

To correlate the damage classes with the EF Scale, 10 structures within each damage class were randomly 

selected and assigned an EF rating using the EF Scale process. The 10 structures in each damage class 

were assumed to be representative of the entire population of structures within each class. The summary 

statistics for each damage class are shown in Table 2–3, along with an EF number corresponding with the 

average wind speed within each class. As expected, as the damage classes increase in intensity, the 

estimated wind speeds (and EF numbers) increase as well. The mean wind speeds for the damage classes 

were as follows: 78 mph (EF–0) for “light,” 93 mph (EF–1) for “medium,” 117 mph (EF–2) for 

“heavy/totaled,” and 144 mph (EF–3) for “demolished.” 

62 E. Stitz, Regional Technical Manager – Central Region, Pictometry®, personal communication, October 2012. 

NIST NCSTAR 3, Joplin Tornado Investigation 37 
 

 

 

 

 

 

 

 

Chapter 2 

Light

St. Marys Elementary 

School

Light Medium Heavy/Totaled Demolished

Data Source: Pictometry®. Used with permission. 

Figure 2–15. Building footprints in part of Joplin showing damage classes. St. Mary’s 

Catholic Elementary School (red box) shown for reference. Area shown is approximately 

1.0 miles west to east and 0.8 miles north to south. 

Table 2–3. Wind speed statistics and numbers of structures estimated for residential 

damage levels using EF Scale. 

General Damage Classes 

Statistics Light Medium Heavy/Totaled Demolished 

Mean wind speed – mph (m/s) 78 (34) 93 (42) 117 (52) 144 (64) 

Standard Deviation – mph (m/s) 8 (3.6) 15 (6.7) 11 (4.9) 23 (10) 

Range – mph (m/s) 65–85 (29–38) 85–120 (38–54) 95–130 (42 – 58) 110–175 (49–78) 

Average EF Number 0 1 2 3 

No. of Residential Structuresa 3,498 732 1,119 2,062 

a. Data source: Pictometry ®. Used with permission. Analysis by NIST. 

38 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

Residential structures categorized as “demolished” had the highest range of estimated wind speeds (110– 

175 mph or 49–78 m/s) and the most variable wind speeds (23 mph or 10 m/s standard deviation) 

according to the EF estimates. Marshall et al. (2012) rated over 7,000 residential structures affected by 

the Joplin tornado using pre– and post–storm information and rated 22 structures as sustaining EF–5 

damage. This small number of structures relative to the total number of damaged structures is not out of 

line with the estimates from the sample rated by NIST, assuming a normal distribution for the wind speed 

statistics shown in Table 2–3. A table that includes all 40 of the structures rated using this method is 

provided in Appendix B. A second indirect method (i.e., tree fall) used to estimate wind speeds in the 

Joplin tornado is discussed in the next section. 

2.3.4.2 Tornado Wind Field Model 

Background—

Estimating wind speeds from tree fall was first attempted using a Rankine vortex model (Sec. 2.3.1) in 

Europe by Letzmann (Beck and Dotzek 2010). Hardwood (e.g., oak, maple, birch, ash) and softwood 

(e.g., pine, spruce, fir, hemlock) trees constitute two of the DIs in the EF Scale, with degrees of damage 

ranging from small limbs broken to debarking of the tree. Detailed analysis performed by Letzmann 

based on tree fall went largely unexplored until recently (Holland et al. 2006; Bech 2009; Beck and 

Dotzek 2010; Karstens et al., 2013), as questions regarding estimating wind speeds from damage persist 

(Dotzek 2009). Recent studies have incorporated (along with the Rankine model) a detailed tree breakage 

model that takes into account such parameters as crown height and width and tree spacing as well as 

parameters conveying the tree’s resistance to load (in this case wind load) and terrain characteristics. For 

example, in Holland et al. (2006), both the tree fall and wind field models were used in a simulated case 

where tree–specific parameters were known. 

Model Background, Assumptions, and Limitations—

As mentioned in Beck and Dotzek (2010) and by Peterson (2003) a limited number of studies have been 

performed on specific types of trees to test their resistance to wind. In addition, since most studies are 

undertaken in forests, it is difficult to apply them to tree falls in urban settings due to a number of factors 

including root growth, spacing between trees, and varying numbers of species (Peterson, 2003). 

Variability in tree characteristics (i.e., spacing, soil conditions, tree dynamics, etc.) therefore has not been 

taken into account in this study. Due to these uncertainties, an average critical tree fall wind speed (i.e., 

the average wind speed when trees fall) as suggested by Beck and Dotzek (2010) was used in construction 

of the Joplin tornado wind field model. 

In the initial stages of the Joplin tornado touchdown, multiple vortices were documented by videos, 

photos and eyewitness and spotter reports.63 Analysis of tree fall patterns near the beginning of the 

tornado track as shown in Fig. 1–4 indicates at least five to six vortices were present in early stages of the 

tornado. Where multiple vortices clearly occurred in the early stages of the tornado, wind speeds were 

not modeled. It is acknowledged that the multiple vortices may have been responsible for some of the 

highest actual wind speeds in the Joplin tornado. 

63 NOAA (www.crh.noaa.gov/sgf/?n=event_2011may22_survey). 

NIST NCSTAR 3, Joplin Tornado Investigation 39 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

The Rankine vortex model used is a simplification of the actual flow fields. The Joplin tornado possessed 

multiple vortices when it began and may have been a two–celled tornado structure (Wood and Brown, 

2011) with a stagnant core as it progressed through Joplin (Karstens et al., 2013). This two–celled 

structure is not assumed in the Rankine model. It is also likely that the Joplin tornado had asymmetric 

velocity patterns and significant variations that were a function of time and space, as has been identified 

in numerous other tornadoes (e.g., Wurman and Gill 2000). 

No terrain corrections were performed, although surface elevation changes such as hills or valleys may 

channel or reduce the flow and likely alter the tornado vortex dynamics (Lewellen 2012). In addition, no 

near–surface debris effects were considered, the vertical profile of the horizontal wind speed was assumed 

to be uniform, and the horizontal wind speeds were assumed to be representative of a “peak” (i.e., 3– 

second gust) wind speed. No vertical wind speeds were considered, but are another topic for future 

research as noted by Van de Lindt (2013), as they may add a significant component to the wind speed and 

adversely affect wind loading on structures. 

Joplin Tornado Model Initialization—

A wind field model using a Rankine vortex was developed using a number of parameters as input 

variables. An initial range was used for each of the input variables to account for uncertainty. The 

justifications for the parameter ranges are discussed after a brief description of each input parameter: 

	 Translation speed, translation direction and tornado location (VT, θT, X, Y): These parameters 

represent the speed and direction of tornado movement as well as the location of the center of 

the tornado (also described in Sec. 2.3.2). 

The average translation speed, VT, was estimated to be around 30 mph (13.4 m/s). This speed 

is based on radar information provided by NWS Springfield and on surveillance video 

provided by Joplin City Schools that contained time–stamp information for two schools 

approximately 3 miles (4.8 km) apart. Based on the time stamps it took approximately 6 

minutes for the tornado to travel between those two schools, for an average VT of 30 mph 

(13.4 m/s). There was some variability in VT noted in the NWS radar information. This 

variability is included in the model as ± 5 mph (2.2 m/s). 

The translation direction, θT, and associated initial tornado center location (X, Y) were 

inferred from the NWS radar information and visual inspection of the damage swath from 

aerial photos. The overall tornado translation direction is illustrated later in Fig. 2–21. In 

addition, the location of the tornado center was also compared to locations at which 

interviewees mentioned experiencing a period of strong wind speeds, a relative calm, and 

then a subsequent increase in wind speeds. These reports were interpreted as references to 

the tornado "eye” (Burgess et al. 2002), an area of relatively calm winds within the tornado 

vortex that is noted in larger tornadoes. This relatively calm area is illustrated in the Rankine 

vortex model near R/RMW=0 in Fig. 2–10. The location of the tornado center was slightly 

modified, if necessary, to take into account general locations where interviewees reported 

experiencing the tornado eye. Also, in areas where the tornado maintained a consistent 

direction (based on damage patterns) for a relatively long period of time, the tornado center 

was assumed to pass near the “convergence line” in the tree fall patterns. The convergence 

line will be discussed later in this section. 

40 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

	 Alpha (α): This is the angle between Vr and Vmax in Fig. 2–11. The angle is used to calculate 

radial and tangential components as described in Sec. 2.3.2. 

Initial ranges for α were based on comparing general tree fall patterns described in the 

literature (Beck and Dotzek 2010; Holland et al. 2006) with the patterns observed in Joplin. 

This comparison suggested an α value of between 0 and 90 degrees. Typical engineering 

models of tornado wind flow (ANS 2011) assume that α = 90 degrees, or a purely tangential 

flow. Therefore a range from 0 degrees to 90 degrees was initially set for α. 

	 Phi (φ): Phi is the decay exponent of the Rankine vortex (described in Sec. 2.3.2). 

The value of φ used in tree fall studies has typically been 1.0, on the basis of conservation of 

momentum (Beck and Dotzek 2010). However, in studies of natural vortex phenomena this 

exponent was found to be less than one. In fact, multiple studies of both tornadoes (Bluestein 

2007; Bluestein et al. 2003; Kosiba and Wurman 2010; Wurman and Alexander 2005) and 

hurricanes (Mallen et al. 2005) have shown exponents generally ranging from 0.5 to 0.7. For 

this study, the initial range of φ was 0.4 to 1.0. 

Radius of maximum wind (RMW): This refers to the radius from the tornado center to 

maximum wind speed (described in Sec. 2.3.2). Values of RMW were initially estimated from 

the width of significant damage (i.e., large amounts of debris) observed from aerial photos. 

Half the width of the significantly damaged area was used to set initial values of RMW. 

Therefore values of RMW varied along the tornado path proportional to the widths of the 

damaged areas. 

	 Rotation–translation ratio (Gmax): This is the ratio between the maximum wind speed from 

the Rankine vortex model, Vmax, and the translational wind speed, VT. Similar to α, initial 

ranges for Gmax were based on comparing tree fall patterns in previous literature and other 

tornado events (Beck and Dotzek 2010; Holland et al. 2006; Bech 2009) with the patterns 

observed in Joplin. The prior studies suggested a Gmax value between 3.0 and 5.0. Letzmann 

(Beck and Dotzek 2010) set an upper limit of Gmax at approximately 6.0. Therefore a range of 

Gmax from 3.0 to 6.0 was initially set. 

	 Critical wind speed (Vcrit): This is the average wind speed needed to cause a tree to fall. 

Initial ranges for Vcrit were estimated using a combination of information from Peterson,64 

EF–Scale information regarding tree damage (TTU 2006), and measured wind speed data 

from a windstorm that affected Joplin on May 8, 2009 that had a measured peak wind speed 

of 85 mph (37 m/s). The measured wind speed data were coupled with observer relayed 

storm reports denoting tree fall in the Joplin area.65 The initial range of Vcrit was set at 70 

mph (31.3 m/s) to 110 mph (49.2 m/s). 

64 C. J. Peterson, personal communication, May 2012. 65 NOAA (http://www.spc.noaa.gov/climo/reports/090508_rpts.html). 

NIST NCSTAR 3, Joplin Tornado Investigation 41 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

 Maximum wind speed (቙ሁ): In the model, the overall maximum wind speed is calculated using 

Gmax (related to the maximum wind speed from the Rankine model) and VT . This calculation 

is shown in Equation 2.2. 

቙ሁ ቭ ቛቊሁድሌ ቦ ኔቜ቙ዮ (2.2) 

Given the initial ranges of Gmax, the maximum wind speed using Eqn. 2.2 for the Joplin 

tornado could be no more than 245 mph (110 m/s) and no less than 100 mph (45 m/s). 

Grid development 

In order to enable the calculation of wind speed and direction at specific points throughout Joplin as well 

as to compare outputs of the wind field model with tree fall observations in Joplin, a grid system was 

created (see Appendix C for additional for information). Each grid point represented a point (i.e., tree) in 

the model where a time history of wind speed and direction can be estimated, along with a tree fall 

direction. Grid points were initially located 0.02 miles (about 106 ft or 32 m) apart to be consistent with 

tree fall observations in Joplin (shown later in Table 2–4) and subsequently to determine Rankine model 

parameters at specific locations as defined in Appendix D Table D–1. Once these parameters were 

determined the grid was widened to 0.05 miles to account for the uncertainty in the tornado center 

location as well as for computational speed. Figure 2-16 illustrates grid points spaced 0.05 miles (264 ft, 

80 m) apart throughout Joplin. The origin of the grid is located along Schifferdecker Ave 1⁄4 mile 

(approximately 400 m) south of the Schifferdecker Ave. and 32nd St. intersection. The grid extends 6.2 

miles east and 2.0 miles north. The eastern end of the grid was located approximately along Kenser Road. 

The boundaries of the grid were chosen to enable modeling of the tornado throughout Joplin. 

Aerial image © 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 2–16. Grid system for tree fall analysis in Joplin. Each dot denotes a tree/wind– 

field point spaced at every 0.05 miles. The grid extends 6.2 miles west to east and 2.0 

miles north to south. 

Tornado center translation through grid 

Starting at the estimated beginning of the tornado track, the center of the tornado was “moved” 

throughout Joplin. The tornado center was moved in increments of 0.01 miles (about 15 m or 50 ft) in the 

x–direction and a corresponding distance in the y–direction based on the translation direction, θT, in 

comparison to 270 degrees (from due west) as shown in later in Fig. 2–21. For example, if θT was 250 

42 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

degrees, the y–direction movement would be 0.01 miles  tan (270 – 250). The tornado center moves this 

distance at the translation speed of the tornado, VT. From the information above, a time step can be 

calculated. For example, advancing the tornado 0.01 miles moving at 30 mph (13.4 m/s) gives a time step 

of 0.01 miles  (1/30 mph)  3,600 s = 1.2 s. An example of the Rankine model translating through a 

generic 0.05–mile–spaced grid point system is shown in Fig. 2–17. The outputs and results of moving the 

tornado through the grid are discussed in the next section, as are the changes in translation direction 

throughout the Joplin tornado. 

Full factorial design 

All combinations of parameters were input into the Rankine vortex model (Eq. 2.1) by using full factorial 

design (Milton and Arnold 2003). Full factorial design ensured that each parameter combination was 

tested, one combination at a time, by translating the Rankine vortex through the grid. Full factorial design 

also allows best estimates of Rankine vortex parameters to be determined based on comparisons with 

observations of tree fall in Joplin, and identifies the most influential parameters. 

Model Results—

Model outputs 

For each time step, a wind speed from the Rankine model (Vcir) was estimated by using Eq. 2.1. Both Vcir 

and VT were then broken up into x and y components. The x and y components from Vcir were then added 

to the x and y components from VT to arrive at the total x and y components of wind speed. The total 

magnitude of the horizontal wind speed (V) was then calculated from its x and y components. The wind 

direction (β) was also calculated from the x and y components of wind speed. 

When a wind speed (V) at a grid point exceeds Vcrit, the tree falls in the direction of wind at that time step, 

denoted by the angle β. Figure 2–17 illustrates the procedure, where the contoured values represent wind 

speed (V), the black arrows represent the direction of tree fall (when V exceeds Vcrit), and the red arrows 

illustrate the wind direction (β) at the current time step. 

As each model run (parameter combination of the Rankine vortex) completes translation through the grid, 

outputs are generated including wind speed and direction time histories at each grid point and the wind 

direction associated with the tree fall (β), provided Vcrit is reached. The numbers and locations (grid 

points) of fallen trees are also generated. From these outputs, the derived model outputs are produced to 

compare with actual observations of tree fall in Joplin. These tree fall observations are discussed in the 

following paragraphs. 

Joplin observations 

Nearly 10,000 trees were estimated to have been felled by the tornado in Joplin (Karstens et al. 2013), 

most of which were uprooted, as determined from aerial photos. The large number of trees located 

throughout Joplin made it attractive to estimate near–surface wind speeds using the Rankine vortex model 

and associated tree fall based on the methodology described in the previous section. 

NIST NCSTAR 3, Joplin Tornado Investigation 43 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

Figure 2–17. Grid 

overlaid with Rankine 

vortex model results. 

Red arrows represent 

current wind direction, 

black arrows represent 

direction of tree fall, 

and contouring 

illustrates wind speed 

field. 

The directions of tree fall for approximately 5,000 felled trees throughout the tornado path were drawn 

digitally using post–storm aerial photos. Figure 2–18 shows the tree fall patterns observed between 20th 

and 32nd streets just east of Schifferdecker Avenue. A non–exhaustive list of the types of trees that fell in 

the Joplin tornado, as determined by field surveys, aerial photos, and interview transcripts, is as follows: 

American and Chinese elm, American sycamore, yellow poplar, shagbark hickory, white oak, and 

Bradford pear. 

Based on the observed tree fall in Joplin, three model output parameters were developed and compared to 

the observations in Joplin: 

	 Damage width (DW): This parameter refers to the width of the swath of felled trees (north– 

south alignment). It was estimated by locating the furthest extent in either direction where it 

appeared that most (i.e., more than 50 percent) of trees had fallen. This spatial dimension 

was measured at a minimum of 0.02–mile increments. 

	 Damage ratio (DR): This is the ratio of DW on either side (i.e., south and north) of the 

"convergence line" (shown in Fig. 2–19). The convergence line was estimated to be the 

location where the patterns of tree fall on either side of the tornado center converge. 

	 Tree fall directions (β1...βn): The tree fall directions were estimated from calculating the 

angle associated with the direction of tree fall as drawn in ArcGIS. If possible, the fall 

direction of three to four trees in close proximity (0.01 miles, or 30 m) were averaged to 

calculate a reasonable estimate of β. For this work, angles of 90 degrees (tree fallen 

westward) and 180 degrees (tree fallen northward) were used for comparison. 

44 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

Chapter 2 

Figure 2–18. Observed tree fall pattern between 20th and 32nd streets just east of 

Schifferdecker Ave. Area is approximately 0.5 miles west to east by 1.0 miles north to 

south. 

The parameters DW, DR, β were estimated at 10 locations in Joplin from aerial photographs using the 

methods described above, and presented in Table 2–4. For β, the table shows locations (in the y– 

direction) that correspond to the 90– and 180–degree tree fall directions. The values in the “β” columns 

are distances in miles either south (–) or north (+) (i.e., in the y–direction) of the convergence line. An 

example comparison at one location between model outputs and observed values for DW, DR, β is shown 

in Fig. 2–19. 

NIST NCSTAR 3, Joplin Tornado Investigation 45 
 

 

 

 

 

 

 

 

Chapter 2 

Table 2–4. Observed Joplin tree fall metrics. 

Tornado Center 

Location (X) 

(miles) 

Damage Width 

(DW) (miles) 

Damage Ratio 

(DR) 

Locations of Tree Fall Directions 

(miles S (–) or N (+) of convergence line) 

β (90 degrees) β (180 degrees) 

0.69 0.55 2 –0.02 –0.3 

0.88 0.6 2 –0.04 –0.38 

1.01 0.7 2 –0.04 –0.42 

1.22 0.75 2 –0.02 –0.32 

2.09 0.9 2 0 –0.28 

3.14 1 2.3 –0.06 –0.46 

3.69 0.85 2.3 0 –0.38 

6.01 1 2 +0.04 –0.36 

6.47 1 2 +0.12 –0.18 

6.77 1 2 +0.16 –0.18 

Model comparisons to Joplin observations 

Using full factorial design, main– and interaction–effects plots (Box et al. 2005) were created by NIST. 

Main and interaction effects illustrate the effects of varying the input parameters of the Rankine vortex 

model (in this case RMW, α, etc.) on the final output parameters that can then be compared to the 

observations in Joplin (DR, DW, β). Additional details on the comparison between the Rankine vortex 

model and observations used in selection of the final model parameters are provided in Appendix D. 

These details include a general explanation and interpretation of main and interaction effects plots. Based 

on the generation of Rankine vortex input parameter combinations by the use of full factorial design, the 

variability in output parameters (DR, DW, β) is discussed. An example of the use of main and interaction 

effects plots to select of “best matches” (i.e., narrowed parameter ranges) of Rankine vortex input 

parameters (RMW, α, etc.) to observed tree fall metrics (Table 2–4) throughout Joplin is also discussed. 

The process of selecting “best matches” is illustrated for a specific set of north–south grid points in 

Joplin. These “best matches” for locations throughout Joplin are listed in Appendix D, Table D–1. 

The “best matches” of the Rankine vortex input parameters were used to calculate wind speed and wind 

direction time histories at each grid point in Joplin based on Eq. 2.1. A specific grid point (#1175, X = 

2.1 miles, Y = 0.45 miles, located near the center of the path of the tornado at the southwest corner of W. 

26th St. and S. Jackson Ave, two block east of St. John’s Regional Medical Center) was chosen to 

illustrate the variation in wind speed and wind direction based on Rankine vortex parameter combinations 

created in the factorial design. The graphs in Fig. 2–20 show the ranges and “best estimate” (i.e. average 

value of best matches) of wind speed and direction. Note the differences in time and magnitude among 

the maximum wind speeds in the three time series. These are due to the translational speed (VT) of the 

tornado. The translational speed of the tornado is also included in the final estimation of wind speed (V), 

and contributes heavily to the uncertainty of maximum wind speed and maximum duration of a given 

wind speed as will be discussed later. Wind direction does not have as much uncertainty as wind speed 

for this specific grid point. Due to the many directional changes (changes in damage path) within the 

track of the Joplin tornado, however (Fig. 2–21), it was difficult to pinpoint an exact location when the 

tornado changed direction. When interpreting the final wind speed and wind direction estimates from the 

wind field model, uncertainty should include values from one grid point (264 ft, 80 m) away in any 

direction. 

46 NIST NCSTAR 3, Joplin Tornado Investigation 
 

Chapter 2 

Figure 2–19. Example of procedure for comparing observed tree fall to modeled tree fall.
 

Output parameters are also listed.
 

NIST NCSTAR 3, Joplin Tornado Investigation 47 
 

 

 

 

 

 

 

E. 32nd St. S. Duquesne St.

E. 15th St. Schiffererdecker Ave. 0 0.5 1 1.5 2

Miles

 

Chapter 2 

0 200 400 600 800 1000 1200

100

150

200

250

300

350

Time From Tornado Start (sec)

Wind Direction (deg)

0 200 400 600 800 1000

0

20

40

60

80

100

120

140

160

180

200

220

Time From Tornado Start (sec)

Wind Speed (mph)

Figure 2–20. Ranges and best estimate of wind speed (left) and associated wind 

direction (right) for Grid Point #1175 (southwest corner of W. 26th St. and S. Jackson 

Ave). Best estimates are the bold traces on each plot. 

Aerial image © 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 2–21. Translation direction (θT) changes in the Joplin tornado. Numbers are
 

approximate directions in degrees. White line indicates estimated center of
 

tornado path. The area in the figure is approximately 6.2 miles west to east and 2.0 miles
 

north to south.
 

Wind Field Characterization—

Overall 

Based on the examples above, the range and best estimate of maximum wind speed values, and associated 

wind direction values, as illustrated in Fig. 2–20, were recorded for each grid point. For the chosen 

reference grid point (#1175) the range of maximum wind speed was 135 mph to 210 mph, while the best 

estimated value was between 170 and 175 mph. For this grid point therefore, the range of wind speeds 

on either side of the best estimate was up to 25 percent of the best estimated maximum wind speed. The 

uncertainties in maximum wind speed are discussed later in this chapter. 

Figure 2–22 provides a closer examination of Fig. 2–20 using best estimated wind speeds. This location 

was within the RMW (likely in the corner flow region or Region III as illustrated from a general case in 

48 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

Chapter 2 

Fig. 2–9). According to the model, this grid point was near the possible “eye” of the tornado. As the 

tornado approached wind speeds increased to approximately 115 mph to 120 mph then dropped rapidly to 

0 200 400 600 800 1000

20

40

60

80

100

120

140

160

Time From Tornado Start (sec)

Wind Speed (mph)

0 200 400 600 800 1000

140

160

180

200

220

240

260

280

300

Wind Speed 

Wind Direction (deg)

Wind Direction 

Figure 2–22. Example of a modeled best estimate of tornado wind speed and direction 

time history for Grid Point #1175 (southwest corner of W. 26th St. and S. Jackson Ave). 

speeds below 60 mph when the tornado center was near, and increased on the back side of the tornado to 

a maximum of approximately 175 mph. Between the first and second peaks, the wind direction shifted 

nearly 180 degrees in approximately 30 seconds to 40 seconds. Time histories for every grid point with 

best estimated wind speed and direction values (and more information on the wind field modeling 

process) will be available through the NIST Disaster and Failure Studies Event Data Repository web site 

(http://www.nist.gov/el/disasterstudies/repository_home.cfm) when the Joplin Tornado Repository is 

completed. Best estimated time histories nearest to structures surveyed by NIST can be found in 

Appendix E. These time histories were also used to study both structural (Chapter 3) and human (Chapter 

4) responses to the Joplin tornado. 

The best estimated maximum wind speed at each grid point was rounded to the nearest 5 mph, (e.g., 175 

mph for grid point #1175) loaded into ArcGIS, and overlaid on post–storm aerial photos. From the 

maximum wind speed information, two shapefiles were created in ArcGIS. The first shapefile shows the 

grid points in the wind field estimation colored by their best estimated maximum wind speed value. This 

wind field estimation is illustrated in Fig. 2–23. The coloration is based on wind speed ranges outlined in 

the EF Scale. The second shapefile was created by drawing polygons around areas that were within the 

wind speed ranges prescribed by the EF Scale. These polygons are shown in Fig. 2–24. 

NIST NCSTAR 3, Joplin Tornado Investigation 49 
 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

Important Note: The methodology for and generation of the wind field from tree fall as discussed above 

was completely independent of the EF Scale with the exception of minor input for Vcrit. However, the 

wind speed ranges associated with different EF numbers (e.g., EF–0, EF–1, . . . EF–5) in the EF Scale are 

0 0.5 1 1.5 2

Miles

Aerial image © 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 2–23. Estimated maximum wind speed grid points from tornado wind field model 

grid points grouped by EF Scale. The solid black line represents the estimated tornado 

center. The area in the figure is approximately 6.2 miles west to east and 2.0 miles north 

to south. 

Aerial image © 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 2–24. Estimated maximum wind speed polygons from tornado wind field model grouped 

by EF Scale. The solid black line represents the estimated tornado center. The area in the 

figure is approximately 6.2 miles west to east and 2.0 miles north to south. 

helpful for comparing the estimated wind field in the Joplin tornado to other tornadoes in a historical 

context as well as to other tornado wind field models. The EF Scale is a damage–based scale only. For 

example, an estimated wind speed of 175 mph from tree fall should not be interpreted as an EF–4 wind 

speed as EF–4 wind speed estimates are derived from structural damage only. The estimated 175 mph 

wind speed should be interpreted as a wind speed associated with the range of EF–4 wind speeds in the 

EF Scale. 

50 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

0 – 10 s

10 – 20 s

20 – 30 s

30 – 45 s

> 45 s

E. 32nd St. S. Duquesne St. 

E. 15th St.

0 0.5 1 1.5 2

Miles

 

Chapter 2 

Duration of high wind speeds 

Low phi values (φ = 0.6 to 0.7), along with a relatively slow translation speed (VT = 25 mph to 35 mph) 

and the high radial component to the flow (α = 15 degrees to 25 degrees) suggest that wind speeds 

remained above a certain level for a relatively long time and over a large area in the Joplin tornado, a 

notion that is expanded upon in the next paragraph. For example, the Rankine model with a φ value of 

0.7 predicts that once the wind speed reaches its peak value, it doesn’t drop off as fast as for a φ value of 

1.0, i.e., high wind speeds extend farther out from the center of the tornado (Figure 2–25). 

Figure 2–25. Illustration of 

differences in Rankine 

vortex model given φ

parameter. 

The duration of damaging winds can play a significant role in overall damage states (Kopp and Morrison 

2011). Figure 2–26 shows the estimated amount of time that the modeled wind speeds were at an EF–2 

level or above (≥ 49.2 m/s or 110 mph). Each time step that was at or above the EF–2 level was summed 

to estimate the duration. The best estimated longest duration of EF–2 or greater wind speeds in the Joplin 

tornado was approximately 67 seconds, with a range of 33 seconds to 107 seconds considering the 

uncertainty in the input parameter values used in the wind field model. The longest duration of damaging 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 2–26. Best estimate of duration of wind speeds greater than or equal to EF–2 

(≥ 110 mph). Green line shows estimated tornado center. The area in the figure is 

approximately 6.2 miles west to east and 2.0 miles north to south. 

NIST NCSTAR 3, Joplin Tornado Investigation 51 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

wind speeds was mainly south of the estimated tornado center shown in Fig. 2–26. The majority of areas 

that experienced any EF–2 or greater wind speeds encountered over 30 seconds of such winds due to the 

structure of the wind field. 

With regard to spatial extent, the total modeled area affected by wind speeds EF–0 or higher (≥ 65 mph 

(29.1 m/s)) during the Joplin tornado was estimated to be 10.5 square miles. Table 2–5 presents 

information about the areas affected by each of the EF wind speed ranges. The table also provides the 

percentages of affected areas expected under each EF level in hypothetical EF–4 and EF–5 tornadoes in 

probabilistic assessments of tornado hazards using historical data (NRC 2007). The Joplin tornado had 

larger areas subjected to the highest wind speeds compared to the theoretical tornadoes in NRC (2007). 

Aspects of the spatial dimensions of tornadoes and associated damage compared to the Joplin tornado are 

discussed further in Sec. 2.4. 

Table 2–5. Estimated areas affected by wind speeds falling within the EF wind–speed 

ranges, within Joplin grid system and in theoretical EF–4 and EF–5 tornadoes. 

EF Number 

Area 

Affecteda 

(sq. mi.) 

Percent of 

Area 

Affectedb 

Area with 

Maximum 

Wind Speedc 

(sq. mi.) 

Percent of 

Area with 

Maximum 

Wind Speedd 

Percent of 

Theoretical 

EF–4 Area 

with 

Maximum 

Wind Speede 

Percent of 

Theoretical 

EF–5 Area 

With 

Maximum 

Wind Speedf 

0 10.5 100 5.2 49 54.3 53.8 

1 5.3 51 2.2 20 23.8 22.3 

2 3.1 30 0.9 9 13.1 11.9 

3 2.2 21 1.1 11 5.6 7.0 

4 1.1 11 1.1 11 3.2 3.3 

5 0.0 0 0.0 0 0.0 1.7 

a. Total area within Joplin grid system that was affected by winds falling within the wind–speed range of the specified EF 

number or a higher EF number. 

b. Percentage of the total area within Joplin grid system that was affected by winds falling within the wind–speed range of the 

specified EF number or a higher EF number. 

c.	 Total area within Joplin grid system where the maximum wind speed experienced during the Joplin tornado fell within the 

range of the specified EF number. 

d. Percentage of the total area within Joplin grid system where the maximum wind speed fell within the range of the specified 

EF number. 

e. Percentage of the total area affected by a theoretical EF–4 tornado (NRC 2007) where the maximum wind speed fell within 

the range of the specified EF number. 

f.	 Percentage of the total area affected by a theoretical EF–5 tornado (NRC 2007) where the maximum wind speed fell within 

the range of the specified EF number. 

Maximum wind speed (቙ሁ) 

The tree fall model indicated that the best estimated maximum wind speed anywhere in the tornado was 

between 170 and 175 mph, within a range of modeled maximum wind speeds of 135 mph to 210 mph. 

For grid points that were within the RMW on some model runs and outside of the RMW on others (e.g., 

locations between 0.14 miles and 0.18 miles from the tornado center), wind speed ranges around the best 

estimate were as high as ± 45 mph. As stated earlier, a great deal of the total model uncertainty in wind 

52 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

speed is due to the range of the translation speed (VT). In the factorial analysis, there are three distinct 

maximum wind speed ranges that are produced. These ranges are based on three different values of VT. 

These ranges are illustrated in Fig. 2–27 for grid point #1175. If VT was kept fixed at the average value 

of 30 mph, the estimated range produced for areas in Joplin that experienced the highest wind speeds was 

approximately 160 mph to 180 mph. In other words, up to 80 percent of the model uncertainty is due to 

uncertainty in VT. The remaining uncertainty is in the Gmax parameter, the only other variable used in the 

calculation of ቙ሁ(Eqn. 2.2). This estimate does not include the model assumptions and limitations 

mentioned earlier in this section. The ranges in Fig. 2–27 were developed using range values for all six 

input parameters as well as the best estimated parameter value for a total of 729 (36

) factorial runs to 

show the differences in V using different values of VT. The coefficient of variation (COV) for this 

particular grid point considering all values of VT was approximately 0.14. Using only the ranges values 

with 64 (26

) factorial runs, the COV was approximately 0.17. These values of the COV were consistent 

for all grid points analyzed. It should be noted that the uniform distributions of maximum wind speed are 

due to the fact that the values of the input parameters (VT and Gmax in this case) in the factorial design 

were equally likely as a result of the factorial design (uniform distribution). No specific distribution was 

given to the input parameters. The nine (32

) different combinations of maximum wind speed, using the 

range values of VT and Gmax are shown as red dots in Fig. 2–27. 

130 140 150 160 170 180 190 200 210 220

0

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

9 0

100

Wind Speed (mph) No. of Factorial Runs

VT = 25 mph VT = 30 mph VT = 35 mph

Figure 2–27. Three distinct ranges of maximum wind speed based on different values of 

translational speed (VT) for Grid Point #1175. Red dots illustrate the combinations of V 

using the range values of VT and Gmax. 

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Chapter 2 

Model Comparisons with Other Estimates—

It should be noted that although comparisons are made here between wind speeds generated from the 

wind field–tree fall model and other tornado wind speed estimations both in Joplin and elsewhere, the 

Joplin tornado was a rare event in terms of the destruction and loss it caused. In other words, the 

knowledge base on events such as Joplin is lacking, making comparisons difficult and acknowledging our 

understanding is still limited. 

Comparisons with maximum wind speed using EF Scale 

NIST evaluation using the EF Scale for both structures surveyed on the ground and residential structures 

surveyed from aerial photos (see Sec. 2.3.4) yielded similar estimates of maximum wind speed, especially 

the lower half of the maximum wind speed range. The estimated maximum wind speed based on damage 

observed among NIST–surveyed structures was 150 mph ± 15 mph (135 mph to 165 mph) and among 

residential structures was 175 mph. The Springfield NWS office based its estimated maximum wind 

speed of 200+ mph (EF–5) in part on information not contained in the EF Scale such as manhole covers 

and tractor trailers.66 Using tree fall analysis, Karstens et al. (2013) estimated that the maximum wind 

speed in the Joplin tornado exceeded 230 mph, while Roueche and Prevatt (2013) estimated maximum 

wind speeds to be approximately 175 mph to 180 mph using EF–Scale wind speed estimates of residential 

damage fit to a Rankine vortex model. The maximum wind speed estimates explicitly using the EF–scale 

were in general closer to those of the tornado wind field model used in the study as compared to other 

estimation methods. The relatively large difference in maximum wind speed estimates from the other tree 

fall estimation is likely due to the different methodologies employed (e.g., using non–uniform 

distributions for critical tree fall wind speed in Karstens et al., 2013). 

Comparisons with EF–derived wind speeds at specific locations 

Best estimated maximum wind speeds at specific locations in Joplin derived from the wind field model 

were compared to the estimated values of maximum wind speed generated using the EF Scale for selected 

NIST–surveyed structures, as shown in Table 2–6. The table shows the best estimated range of maximum 

wind speeds at each site given that all the structures have significant dimensions. For example, on the 

north side of the Walmart store, wind speeds were best estimated to be 110 mph, while maximum wind 

speeds on the south side were estimated to be 160 mph. Overall, the estimates of wind speeds by tree fall 

were comparable to those estimated by using the EF Scale for NIST–surveyed structures. Estimated time 

histories of wind speed and direction near the center of each of the facilities listed in Table 2–6 can be 

found in Appendix E, and time histories at other locations around each facility are provided in Chapter 3. 

Comparisons with historical and contemporaneous observations 

Observed tree fall metrics were compared with observations in other tornado events as well as the Joplin 

tornado. 

 Damage width (DW): The DW of tree fall in the Joplin area was up to 1.0 mile (about 1,600 

m) in some cases, and was generally above 0.9 miles (about 1,450 m) for most of the Joplin 

tornado path. This width is consistent with the estimate of tornado width (extent of damage) 

for the Joplin tornado determined by the NWS.67 If using the definition of tornado width as 

66 NIST Interview 205, May 2011. 67 NWS (www.crh.noaa.gov/sgf/?n=event_2011may22_survey). 

54 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

being the distance from EF–0 contours perpendicular to the tornado path, the wind field–tree 

fall model produced a width of up to 1.8 miles. 

Table 2–6. NIST best estimate of maximum wind speeds for NIST–surveyed 

structures using tornado wind field model and EF Scale. 

Range of Model–Estimated EF–Scale Point Estimate 

Wind Speeds over the Entire of Wind Speed 

NIST–Surveyed Structure Facility (mph) (mph) 

Walmart 110 (N) – 160 (S) 140 ± 15 

Home Depot 135 (S) – 170 (N) 150 ± 15 

Franklin Technology Center 135 (N) – 160 (S) 150 ± 15 

Joplin High School 155 (N) – 170 (S) 140 ± 15 

SJRMC (Main Buildings) 135 (S) – 170 (N) 140 ± 15 

Joplin East Middle School 160 (N) – 170 (S) 140 ± 15 

Key: SJRMC, St. John’s Regional Medical Center; N, north side; S, south side. 

	 Damage ratio (DR): The DR was about 2.0 to 2.3 in most areas of Joplin. Similar DR values 

were estimated when damage resulting from the Spencer, South Dakota, tornado was 

surveyed (Wurman and Alexander 2005, Part II). These DR values suggest small alpha 

values (more radial inflow) as described previously and discussed below. 

Comparisons using Rankine vortex (input) parameters 

The estimated final ranges of the Rankine vortex (input) parameters were compared, if applicable, to 

other tornado events as well as the Joplin tornado. 

	 Critical wind speed (Vcrit): Average critical tree fall wind speeds that best matched observed 

tree fall patterns ranged from 85 mph to 95 mph. 

	 Radius of maximum wind (RMW): RMW values ranged from 0.07 miles (113 m, 370 ft) in 

the early stages of the tornado to a maximum of 0.18 miles (290 m, 950 ft). For a majority of 

the tornado path, the tornado maintained a best estimated RMW of 0.16 miles (260 m, 845 ft). 

These RMW values are within the limits observed by radar estimation in other violent 

tornadoes (Wurman et al. 2007) and the average value of approximately 260 m is similar to 

that estimated by Karstens et al. (2013) for the Joplin tornado (300 m). 

	 Alpha (α): There was a significant radial component (Vr) (α = 15 degrees to 25 degrees) at 

the near surface (i.e., < 20 m). Although no published radar measurements at less than 20 m 

are noted, Kosiba and Wurman (2010) showed that the radial component of the Spencer, 

South Dakota, tornado increased nearer to the ground. Stronger radial components of tornado 

flow have been theorized to occur in areas with higher surface roughness (Davies-Jones et al., 

2001). The damage ratio (DR) parameter, as mentioned earlier, has a strong relationship with 

the α parameter. Karstens et al. (2013) also estimated highly radial flow in the Joplin tornado 

on the order of 2:1 when compared to tangential velocity. This ratio implies an alpha value 

of approximately 26 degrees. 

NIST NCSTAR 3, Joplin Tornado Investigation 55 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

 Rotation–translation ratio (Gmax): The Gmax parameter was estimated to range from 4.5 to 5.0. 

These values are close to those found in observed tornado tree fall studies that estimated Gmax 

(Beck and Dotzek 2010; Bech et al. 2009). 

 Phi (φ): The analysis suggested that φ ranged from 0.6 to 0.7, instead of being 1.0 as 

suggested by conservation of angular momentum (see Sec. 2.3.2). These values of φ compare 

well with actual vortex phenomena in other tornado events, as mentioned earlier in this 

section. 

2.4 DESCRIPTION OF THE TORNADO HAZARD IN THE UNITED STATES 

2.4.1 Objective 

The objective of Sec. 2.4 is to understand the U.S. tornado hazard at the local, regional, and national 

levels and to place the Joplin tornado in context of this hazard. In pursuit of understanding the tornado 

hazard at the local, regional and national level, Section 2.4.2 briefly discusses tornado climatology. This 

section includes a brief literature review and an introduction to the official NOAA tornado database. The 

NOAA database will be used to assess the tornado hazard. Section 2.4.2 also discusses human and 

economic losses and methods of determining a probability–based tornado hazard in the United States for 

local, regional and national levels including Joplin using the NOAA database. Section 2.4.3 briefly 

highlights how urbanization is affecting considerations of the tornado hazard. 

2.4.2 Tornado Climatology 

A number of studies regarding U.S. tornado climatology are available in the literature (e.g., NRC 2007, 

DOE 2000, Brooks et al. 2003, Dixon et al. 2011). These references all show that the frequency of 

tornadoes is greater east of the Rocky Mountains and west of the Appalachian Mountains, with the 

highest frequencies being in the Great Plains and the Southeast United States. Two references (NRC 

2007; DOE 2000) provide detailed probabilistic analyses for determining the tornado hazard in the United 

States for engineering purposes, which is discussed further in Sec. 2.4.2.3. Two other references (Brooks 

et al. 2003a; Dixon et al. 2011) discuss tornado climatology in a more meteorology–oriented manner. 

2.4.2.1 NOAA Tornado Database 

To provide tornado climatologies for the current study, data covering the period 1950–2011 and 

containing information on U.S. tornadoes were available from the NWS SPC (www.spc.noaa.gov/wcm/). 

These data included, among other elements, the time and date of the tornado touchdown; resulting 

numbers of injuries and fatalities; estimates of property and crop losses; the starting and ending latitude 

and longitude coordinates; and the length and width of the tornado path. 

Note: Tornadoes rated under the old F Scale were assumed to be representative of the same EF–Scale 

value for this report. For example, an F–1 rated tornado corresponds to an EF–1 rated tornado for the 

purposes of this analysis. 

There are some inaccuracies in the NOAA database. A number of these inaccuracies stem from non– 

meteorological reporting changes in the database (Verbout et al., 2006). These changes include a 

56 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

Chapter 2 

reporting increase of EF–0 tornadoes due to increased storm spotters and public awareness, the NWS 

radar system and the improvement of collection efforts for warning verification. Other issues affecting the 

entire database include difficulties in reporting exact locations and times by observers, and rating 

tornadoes with intensity estimated on the basis of observed damage as well as population increases 

(Verbout et al., 2006). 

2.4.2.2 Tornado–Induced Losses 

Human Losses Due to U.S. Tornadoes—

A small number of tornadoes, mostly at the high end of the EF Scale, have caused a majority of the 

fatalities. This is shown in Fig. 2–28, which plots the number of fatalities per tornado by EF–Scale rating 

as well as total number of fatalities by EF rating (in red). There is an approximately log–linear increase in 

fatalities per tornado versus the EF Scale. Approximately 64 percent of all fatalities from tornadoes in the 

United States (1950–2011) have been due to EF–4 or greater tornadoes. A total of 86 percent of fatalities 

have been due to EF–3 or greater tornadoes and 96 percent due to EF–2 or greater tornadoes. On average, 

an EF–5 rated tornado causes approximately 20 fatalities. The EF–5 rated Joplin tornado was responsible 

for 161 fatalities. 

0 1 2 3 4 5

1 0- 4

1 0- 3

1 0- 2

1 0- 1

1 00

1 01

1 02

1 03

1 04

EF Number

Fatalities/Tornado

Total Fatalities

Data Source: NOAA. Analysis by NIST. 

Figure 2–28. Average fatalities per tornado and total fatalities by EF number for the 

period of 1950–2011. 

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Chapter 2 

Economic Losses Due to U.S. Tornadoes—

Damage costs in the NOAA database were given in ranges (e.g., $50,000–$500,000) until 1996. From 

1996 through 2011 specific estimated property loss amounts were provided. Shown in Fig. 2–29 is the 

loss per tornado and total losses (in red) by EF number. As expected, per tornado loss is much greater for 

stronger tornadoes, especially EF–4 and EF–5 tornadoes. For example, an EF–5 tornado, on average, 

causes $100 million in losses. The Joplin tornado was estimated to have caused losses totaling $3 billion. 

As an EF–5 tornado by definition, causes substantial damage, it is expected that a smaller amount of EF– 

5 tornadoes can cause comparable loss to a greater amount of tornadoes with smaller EF numbers. 

Cumulative losses in EF–3 to EF–5 tornadoes are similar to each other and account for over two–thirds 

(67.5%) of all losses in tornadoes. EF–1 and EF–2 tornadoes account for approximately 30% of all losses. 

Figure 2–29, as with fatalities, shows somewhat of a log–linear increase in economic losses per tornado as 

the EF number increases. 

0 1 2 3 4 5

1 0- 2

1 0- 1

1 00

1 01

1 02

1 03

1 04

EF Number

Loss/Tornado ($M)

Total Loss ($M)

Data Source: NOAA. Analysis by NIST. 

Figure 2–29. Average loss per tornado and total loss by EF number for the period of 

1995–2011 (in 2011 dollars). 

2.4.2.3 Tornado Hazard Analysis 

In order to illustrate how the tornado hazard is currently estimated in Joplin and throughout the country, 

the first section discusses “point–based” (i.e. tornado–area based) probabilistic analysis. From this 

analysis, the tornado hazard for Joplin, the region surrounding Joplin, as well as how the tornado hazard 

in Joplin differs from other parts of the country can be determined. The second section describes some 

issues with estimating the tornado hazard using point–based analysis as observed in the Joplin tornado 

58 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

and suggests an alternative way (i.e., spatially based analysis) to estimate the tornado hazard for a 

location such as Joplin, that has many people as well as structures in a relatively concentrated area. 

Point–Based Probabilistic Analysis—

The U.S. Nuclear Regulatory Commission (NRC 2007) and U.S. Department of Energy (DOE 2000) used 

historical tornado data from 1950–2003 and 1950–1998, respectively, to perform a probabilistic analysis 

of the U.S. tornado hazard. The NRC document converted F Scale wind speeds to the EF Scale using a 

relationship shown in the EF–Scale document (TTU 2006). In assessing the probability of tornadoes in 

the United States, both references employed a conditional probability approach in which both the 

probability of a tornado strike and the probability that a wind speed exceeding a certain threshold will 

occur, conditional on a tornado strike. To assess this probability, NRC (2007) examined the 

characterization of reported tornadoes throughout the United States in 1–, 2–, and 4–degree grid squares 

in three distinct regions. These regions, labeled as “western,” “central,” and “eastern” were distinguished 

to better represent the regional characteristics of reported tornadoes based on the historical database. To 

account for spatial variations in intensity a Rankine vortex (see Sec. 2.3.2) coupled with an empirical 

damage model (Reinhold and Ellingwood 1982) were used to determine across–path intensities, while 

only an empirical model was used to determine along–path intensities. 

An illustrated example of how probabilities are typically calculated in the point–based method is provided 

in Fig. 2–30, which shows six tornadoes (red rectangles), with a total damage area of 50 km2 occurring in 

a 1,000 km2 area (noted as “Region X”) over a 50 year period. The underlying probability of occurrence 

of tornadoes Region X is assumed to be uniform throughout the region. Therefore, five percent (50 

km2

/1,000 km2) of the region has been affected by tornadoes over a 50–year period. Under the “point– 

based” probability approach, if 5 percent of the region is affected by tornadoes in 50 years, that yields a 

point probability of Strike of P = 0.05/50 year = 0.001/year, or stated another way, a 1 in 1,000 chance of 

a strike per year. The inverse of the annual probability (1,000 years) is referred to as a mean recurrence 

interval (MRI), which is the average time period of tornado occurrence in this case. 

“Region X”

Region Area = 1000 km2

Total Tornado Area = 50 km2

Time = 50 years

EF-4 Tornado

Tornado Area (EF-2 Area) = 40 km2(4 km2)

EF-1 Tornado

Tornado Area = 2 km2

EF-2 Tornado

Tornado Area (EF-2 Area) = 4 km2(1 km2)

EF-1 Tornado

Tornado Area = 2 km2

EF-0 Tornado

Tornado Area = 1 km2

EF-0 Tornado

Tornado Area = 1 km2

Figure 2–30. Illustration of point–based probability approach. 

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Chapter 2 

In that 50–year period, let’s say that only 10 percent of the total area affected by tornadoes (5 km2 per 

every 50 km2

) was affected by EF–2 winds or greater (shown as white rectangles in Fig. 2–30). 

Therefore, the probability of being affected by EF–2 or greater winds (PEF–2) decreases to by a factor of 

10, on average, once every 10,000 years, for an MRI of 10,000 years. In summary, the point–based 

analysis only considers the overall tornado–affected area and the area affected by a certain wind speed. 

Spatially Based Probabilistic Analysis—

In addition to point–based probability, both the NRC and DOE documents as well as others (Garson et al., 

1976; Twisdale and Dunn, 1983) have considered tornado probabilities that account for structures that 

have some significant area as the probability of being struck by a tornado is greater than that based on 

only tornado dimensions (NRC, 2007). The motivation for spatially based analysis lies largely for 

estimating tornado hazard for critical infrastructure with significant area such as nuclear facilities. Point– 

based methods alone tend to underestimate the hazard (Twisdale and Dunn, 1983) for large structures and 

lifeline facilities such as long span transmission lines. In the spatially–based method, the point–based 

probability is then added to the probability of a tornado strike including the area of the building (i.e. union 

of the tornado and building area). Accounting for building dimension is analogous to saying that if a 

fraction of a large building is affected by a tornado, the entire building is affected. This concept is 

important when considering the spatially based analysis. 

In addition to the previous research noting that point–based methods underestimate the hazard, there were 

a number of observations in the Joplin tornado that would suggest that spatially–based methods may want 

to be considered in estimating the tornado hazard. One observation is the difference between the 

probability of damage based on tornado wind field models (i.e., Rankine vortex) versus the actual 

probability of damaged structures in the Joplin tornado and other strong tornadoes affecting populated 

areas. Tornado hazard models assume that the areal extent of damage is equivalent to the areal extent of 

wind speed. In other words EF–3 damage, for example, is associated with an EF–3 wind speed. In NRC 

(2007), the areal extent of EF–3 or greater damage (wind speed) occurring provided an EF–5 tornado 

strikes is estimated to be about 12 percent of the total tornado path area, and about 9 percent if a tornado 

rated EF–4 strikes. In the 2011 Tuscaloosa tornado (rated EF–4), approximately 14 percent of the total 

affected area was estimated to have experienced damage associated with EF–3 or higher ratings (Prevatt 

et al. 2012). Damage rated F–3 or greater in the 1999 Oklahoma City F–5 tornado was estimated to be 

approximately 40 percent (Speheger et al. 2002). Based on the analysis in Sec. 2.3.4.1 and Table 2–2, the 

Joplin tornado was estimated to have approximately 28 percent EF–3 or greater damage. Table 2–7 

shows the information described above. 

Table 2–7. Percentage of tornado–affected areas exhibiting EF–3 or greater 

damage, given damage occurs and given specified tornado rating. 

Tornado Reference EF–4 Tornado EF–5 Tornado 

Simulated NRC (2007) 9% 12% 

Tuscaloosa (2011) Prevatt et al. (2012) 14% –

Oklahoma City (1999) Speheger et al. (2002) – 40% 

Joplin (2011) NIST – 28% 

60 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

When considering damage classes (e.g., light, medium) instead of EF Scale–based damage in both the 

Tuscaloosa (Prevatt et al. 2012) and Joplin tornadoes, two–thirds of residential structures in Tuscaloosa 

were “destroyed” or had “major damage” and approximately 43 percent of all damaged structures in 

Joplin had similar damage states (e.g., heavy/totaled or demolished). In addition, the F–5 rated Oklahoma 

City tornado in 1999 damaged over 8,000 residential structures, and over one–third (2,750) of those 

structures were considered “destroyed” (Speheger et al. 2002). 

It was estimated that approximately 30 percent of the total tornado–affected area in Joplin experienced 

winds that reached or exceeded speeds associated with EF–2 based on tree fall analysis, while 

approximately 40 percent to 50 percent of structures likely suffered at least EF–2 damage. A likely factor 

causing the additional damage is wind–borne debris. In Joplin, it was estimated that approximately 3 

million cubic yards of debris had to be cleared due to the tornado.68 As expected, in the Joplin tornado, 

debris was found to play a significant role in the performance of residential and commercial structures as 

well as critical facilities (e.g., St. John’s Regional Medical Center). In addition, a number of Joplin 

tornado survivors interviewed by NIST mentioned that the structures they had been in were breached by 

debris. Nearly all fatalities in the Joplin tornado were due to “impacts” (i.e., flying debris, collapsed 

structures). Further information about debris impacts on structures and loss of life is presented in 

Chapters 3 and 4. Breaching of structures by debris (such as by wind–borne debris that breaks through 

windows) has been well documented in previous tornado events and can likely increase the probability 

that nearby structures will sustain damage (Marshall et al. 2002). Another example relevant to using 

spatially–based methods is the fact that approximately 20,000 customers were without power following 

the Joplin tornado according to Empire Electric.69 However, there were only approximately 7,400 

residences damaged due to the tornado. This discrepancy indicates that even though a home may have not 

been damaged by the tornado, effects from the tornado were still felt. 

The information above suggests that in events that affect populated areas, and hence a large number of 

structures, as was the case in Joplin and the other tornado events mentioned, spatially–based rather than 

point–based analyses should be considered when examining the tornado hazard. Described below is a 

methodology using a spatially based approach. 

Instead of calculating an average area affected by tornadoes, by using either path lengths and widths from 

the NOAA database or statistical modeling a spatially based approach would use some larger area such as 

a city, town, or recognized portion of a city or town (e.g., a city ward). Point probability of a strike and 

conditional wind speed probability are now replaced by a regional representation of tornado frequency 

and the area of a city for example. In other words, in a probabilistic sense, if any portion of a city or town 

is affected by a tornado of a given intensity, the entire city or town is affected. 

A general example showing the spatially based method is shown in Fig. 2–31. As in Fig. 2–30, there are 

two tornadoes over a 50–year span that reach EF–2 of greater status in some portion of the tornado path 

(one EF–2 and one EF–4). Considering an area of a community, C, of 40 km2 (Ac) shown in Fig. 2–31, 

gives a spatially–based probability (Ps) of 1/625, or an MRI of 625 years. An MRI of 625 years means 

that some part of “C” will be affected by EF–2 or stronger wind speeds, on average, once every 625 

years. In the point–based approach the MRI was estimated to be 10,000 years. 

68 City of Joplin (http://www.joplinmo.org/DocumentCenter/View/1985). 69 NIST Interview 217, March 2013. 

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Chapter 2 

“Region X”

Region Area = 1000 km2

Total Tornado Area = 50 km2

Time = 50 years

EF-4 Tornado

Tornado Area (EF-2 Area) = 40 km2(4 km2)

EF-1 Tornado

Tornado Area = 2 km2

EF-2 Tornado

Tornado Area (EF-2 Area) = 4 km2(1 km2)

EF-1 Tornado

Tornado Area = 2 km2

EF-0 Tornado

Tornado Area = 1 km2

EF-0 Tornado

Tornado Area = 1 km2

C

Area = 40 km2

Figure 2–31. Example of spatially based approach within a given region. 

Figures 2–30 and 2–31 illustrate the point–based and spatially based approaches through a simplified, 

hypothetical example. An application of the spatially–based method to the United States is described 

below. 

Example of Spatially Based Probabilistic Analysis—

Figure 2–32 illustrates the spatial probability distribution of all tornadoes rated EF–2 or greater in the 

United States from 1950 through 2011 using the official tornado touchdown location record from NOAA. 

There were approximately 11,000 tornadoes rated EF–2 or higher, with a maximum axis extending from 

approximately Oklahoma City eastward to Birmingham, Alabama, as determined from kernel density 

estimation (Silverman 1986). The bandwidth used in the kernel density estimation for the spatial 

probability was 120 km (80 miles) as in Brooks et al. (2003). This general climatology was also 

reflected in both the climatological and probabilistic references discussed previously. 

Over the historical record, some issues have been identified with the tornadoes categorized as F–2 or 

greater (Verbout et al. 2006), which are likely due to some overrating of weaker tornadoes as F–2 before 

1980. Considering spatial probability distributions based on location for the periods 1950–2011 (Fig. 2– 

32) and 1980–2011 (not shown), there do not seem to be any significant differences in locations of EF–2 

or stronger tornadoes. However, there may be a change in the frequency of these tornadoes due to the 

earlier overrating before 1980. The frequency of EF–2 and stronger tornadoes is important in the 

spatially based approach and is discussed in the next paragraph. For the purposes of this work, the 

frequency of 1980–2011 EF–2 and stronger tornadoes was used. 

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Chapter 2 

To assess the frequency of EF–2 or stronger tornadoes, grid points were spaced at 80–mile intervals. The 

touchdown locations of EF–2 or stronger tornadoes that occurred each year from 1980 through 2011 

within an 80–mile radius (an area of slightly over 20,000 square miles) of each grid point were plotted on 

a map of the United States and overlaid with the spatial probability distribution of EF–2 or stronger 

tornado touchdown locations from Fig. 2–32 for reference. The resulting map is shown in Fig. 2–33. 

There is overlapping in spatial area for nearby grid points as a consequence of the grid point/radius 

scheme. This overlap (i.e., tornadoes counted more than once) should help to reduce some variation due 

to non–meteorological factors in tornado touchdown locations when comparing grid points from nearby 

locations. 

Figure 2–33 can also be used to estimate the tornado rate per year for a location within a region. Using 

only EF–3 or greater tornadoes reduces the tornado rate by a factor of approximately two, but, in general, 

the spatial locations do not change. Both EF–4 and EF–5 tornadoes were relatively scarce during the 

course of the NOAA record. Therefore the number of tornadoes per year was not estimated for the 

spatially based approach. Maps showing tornadoes per year for EF–0 to EF–5 tornadoes (separate map 

for each EF number) are available in Appendix F, and can be used in the estimation of MRI in Fig. 2–34. 

As a regional example, the area including Joplin, estimated from the map shown in Fig. 2–33, suggests 

approximately 2.0 EF–2 or stronger tornadoes per year. The four grid points nearest Joplin were 

estimated to contain 1.5, 1.6, 2.2, and 3.1 EF–2 or greater tornadoes per year. This means that the region 

surrounding Joplin (i.e., within an 80–mile radius of the city) averages approximately 2 tornadoes that 

reach EF–2 or stronger status every year. 

Given its tornado climatology it should be no surprise that a number of tornado events affected the Joplin 

region before the 2011 tornado. A recorded F–2 tornado directly affected the city of Joplin on May 5, 

1971. The official NOAA database lists 1 fatality, 60 injuries, and $2.5 million in damage from this 

tornado. 

Three tornado events that all contained at least one EF–3 or stronger tornado occurred within 25 miles of 

Joplin on April 3, 1956, May 4, 2003, and May 10, 2008. The 1956, F–4 tornado caused 118 injuries and 

likely millions of dollars in damage according to the NOAA database. The 2003 event included two F–3 

tornadoes that caused 17 fatalities, 116 injuries, and over $95 million in damage. The 2008 event 

consisted of two EF–4 tornadoes that were within the Joplin region. These tornadoes caused a total of 43 

fatalities and 710 injuries, and the total damage was estimated at $122 million. Table 2–8 summarizes 

key information about these events as well as the 1971 and 2011 tornadoes. 

NIST NCSTAR 3, Joplin Tornado Investigation 63 
 

 

 

Chapter 2 

Data Source: NOAA. Analysis by NIST. 

Figure 2–32. Probability density function of EF–2 or stronger tornadoes. Black dots represent individual touchdown 

locations. Warmer colors represent higher probability and probability values are shown on contour lines. 

64 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

Chapter 2 

Data Source: NOAA. Analysis by NIST. 

Figure 2– 33. Probability density of EF–2 or greater tornadoes from 1980 through 2011 with EF–2 or stronger 

tornadoes per year values shown at each grid point. 

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Table 2–8. Sample of significant tornado events in Joplin region. 

Date Location 

Highest–Rated 

Tornado in Event 

Fatalities 

(Event) 

Injuries 

(Event) 

Damage 

(Event, $M) 

April 3, 1956 Joplin Region F–4 0 118 Unknown 

May 5, 1971 City of Joplin F–2 1 60 2.5 

May 4, 2003 Joplin Region F–3 17 116 95 

May 10, 2008 Joplin Region EF–4 43 710 122 

May 22, 2011 City of Joplin EF–5 161 > 1,000 3,000 

The average number of tornadoes per year taken from the maps in Fig. 2–33 or Appendix F (e.g., Joplin = 

2.0) can be used with a spatial area (e.g., city area) to arrive at an MRI for a tornado affecting any portion 

of that area. A tornado strike on any portion of that area would count as affecting the entire area. This 

spatially based approach becomes especially important when considering large incorporated areas in 

tornado–prone areas. For example, as of 2010, the city of Wichita, Kansas, had an area of approximately 

159 square miles.70 From the map in Fig. 2–33, the region including Wichita can be said to average 

approximately 1.5 EF–2 or stronger tornadoes per year. If the spatially based calculation is used as 

shown in the example in Fig. 2–31, the MRI for a tornado causing at least EF–2 damage anywhere within 

the Wichita city limits is approximately 84 years (1.5 tornadoes/year  159 square miles ÷ 20,000 square 

miles). This MRI for Wichita is illustrated in Figure 2–34. 

Large cities in tornado–prone areas, including Wichita, have been affected by multiple tornadoes rated 

EF–2 or greater. An EF–3 tornado inflicted damage within the city of Wichita in April 201271 and the F– 

5 Andover tornado in April 1991 also caused damage in Wichita. Other relatively large cities within the 

“high” hazard area, such as Birmingham and Tuscaloosa, Alabama, were affected by the April 2011 

tornado outbreak (FEMA 2012) as well as a tornado outbreak in April 1998 (NWS 1998). 

Figure 2–34 graphically shows the spatially based approach, with the tornado frequency per year on the 

x–axis. This information can be taken from Fig. 2–33 or Appendix F depending on the wind speed (i.e., 

EF number) of interest. The y–axis contains the spatial area measure, which can be defined by the user or 

taken from the U.S. Census Bureau if, for example, the area of interest is a city. Different areal measures 

are illustrated in Fig. 2–34 including Wichita, other incorporated areas including Joplin, and the 

traditional point–based (tornado–area) methodology for the Joplin area. The city of Joplin has a spatial 

area of 35.6 square miles according to the U.S. Census Bureau.72 The contoured lines represent the MRI 

as calculated based on tornado frequency and spatial area as shown in Fig. 2–31. 

Once the area used becomes smaller than that of an average tornado (i.e., point–based), using the average 

tornado area in the calculation becomes conservative. Assuming a Poisson process, the probability of an 

EF–2 or stronger tornado affecting any portion of Joplin in a 50–year period is around 15 percent. For 

Wichita, the probability is approximately 45 percent. The tornado rates shown in Fig. 2–34 are for EF–2 

and stronger tornadoes. 

70 United States Census Bureau (http://quickfacts.census.gov/qfd/states/20/2079000.html). 

71 NOAA (http://www.crh.noaa.gov/news/display_cmsstory.php? wfo=ict&storyid=81890&source=0). 

72 United States Census Bureau (http://quickfacts.census.gov/qfd/states/29/2937592.html). 

66 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

Chapter 2 25

25

25 25

25 50

50

50

50

50 300

300

300

300

500

500

500

500

700

700

700

700

1700

1700

1700

1700

2500

2500

2500

5000

5000

5000

10000

10000

10000

100000

Regional Tornado Rate (tornadoes/year)

Area (sq. miles)

Wichita, KS

Joplin, MO

Point Based (EF-2; Joplin Region)

New York, NY

Lima, OH

Boston, MA

Oklahoma City, OK

0.1 0.5 1 2 5 10

10- 1

100

101

102

103

Figure 2– 34. Illustration of spatially based analysis. Contoured values 

are return period (MRI) in years for EF–2 or stronger tornadoes. 

2.4.3 Urbanization of Communities 

With the growing population of the United States and by extension the growing population of urban areas 

as opposed to rural, the vulnerability of communities to tornadoes (and hence their tornado risk) continues 

to increase. By 2011, the numbers of areas that would be considered urban instead of rural had increased 

substantially. This phenomenon was highlighted in a story from the Joplin Globe.73 According to the 

story, the area occupied by Joplin a century ago was only 12.5 square miles and is now 35.6 square miles 

based on Census data, nearly three times the size. This increase in area obviously increases the risk of 

tornado strikes within the city limits. In the future, the square mileage of Joplin and communities like 

Joplin will likely increase further, putting more people and property at risk. Under a spatially based 

approach to tornado hazard analysis, increasing a community’s area by a factor of three increases the 

chances of a tornado strike in any part of that community by the same factor. 

73 www.joplinglobe.com/tornadomay2011/x1315240161/Teams–of–scientists–looking–for–lessons–in–storm–s–aftermath. 

NIST NCSTAR 3, Joplin Tornado Investigation 67 
 

 

 

 

 

 

 

 

 

Chapter 2 

2.5 ENHANCED FUJITA SCALE ASSESSMENT 

2.5.1 Objective 

In Sec. 2.5, the objective is to assess the current guidance, practices, and applications associated with the 

Enhanced Fujita (EF) Scale. As the EF Scale is the official rating scale for tornadoes, information from 

actual events can be drawn upon to help inform this assessment. Section 2.5.2 provides a brief history of 

the F and EF Scales, while Sec. 2.5.3 discusses current EF Scale guidance. Section 2.5.4 focuses on the 

implementation and usage of the EF Scale, especially in recent tornado events, including the Joplin 

tornado. 

2.5.2 History 

The original Fujita (F) Scale was developed by Dr. Ted Fujita from the University of Chicago in 1971 to 

distinguish between tornado intensities and provide a historical and working database for tornado 

climatology (TTU 2006). The F Scale was adopted for use by the NWS in the mid to late 1970s 

(Edwards et al. 2013) and was the primary method of rating tornadoes by assessing damage to structures 

for more than three decades. Although clearly the best method of its time, the F Scale was lacking in 

damage indicators (only photographic indicators of residential damage were initially used), did not 

account for differences in construction quality, rated only the worst damage, and provided no definitive 

correlation between damage and wind speed. These issues led researchers to spearhead an effort to 

reformulate the F Scale. The result of this effort was the Enhanced Fujita Scale (TTU 2006), which was 

implemented by the NWS in February 2007. 

2.5.3 Current Practice/Guidance 

The official document that prescribes how to rate tornadoes using the EF Scale is found on the Texas 

Tech University website (http://www.depts.ttu.edu/nwi/Pubs/FScale/EFScale.pdf). In response to 

criticisms of the original F Scale, the EF Scale document contains 28 damage indicators, or DIs. Each DI 

contains a series of degrees of damage (DODs), which represent the sequence of progressive wind 

damage. This information is also presented in Sec. 2.3.4.1, which discusses the EF ratings developed for 

structures surveyed by NIST following the Joplin tornado. 

In addition, a detailed guide is available from the NWS (2003) on how to perform damage assessments 

and assign an F–Scale rating given the complexities in tornado dynamics, engineered structures, and other 

objects within a tornado’s path. This document also outlines a “how–to” for putting together a storm 

survey team. Although this document was written for the F Scale, it can and should be easily applied to 

the EF Scale. Mentioned in this NWS (2003) document is the use of NWS Quick Response Teams 

(QRT), which can be rapidly deployed in the event of a tornado suspected of producing greater than EF–3 

damage. 

If a tornado is suspected of producing greater than EF–3 damage, official guidance from National 

Weather Service Instruction 10–1604, dated July 29, 2011, states that if a “first review” done by the local 

NWS offices indicates “the situation is of national importance (e.g., a service assessment team may be 

fielded or the survey of damage will have significant scientific interest), they may request their region to 

recommend the activation of an OFCM (Office of the Federal Coordinator for Meteorological Services 

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Chapter 2 

and Supporting Research) PSDA (Post–Storm Data Acquisition) QRT.” The instruction identifies five 

factors that should be considered in evaluating the need for an OFCM PSDA QRT:74 

1. Tornado or wind damage possibly greater than EF–3 

2. Large number of deaths 

3. Catastrophic damage 

4. Profound coastal or inland flooding 

5. Scientific interest 

A QRT was not used in rating the Joplin tornado. However, QRTs were used in other violent tornadoes 

including the Greensburg, Kansas, EF–5 tornado in 2007,75 the Parkersburg, Iowa, EF–5 tornado in 

2008,76 the Alabama tornado outbreak in 2011, which included EF–4 and EF–5 tornadoes (FEMA 2012). 

The Federal Emergency Management Agency (FEMA) recommended in their report on the Alabama 

tornadoes that QRTs should include a design professional (FEMA 2012), as only one of the Alabama 

surveys included an engineer. 

2.5.4 Recent Observations Using the EF Scale 

Although an improvement from its predecessor, the EF Scale has a number of issues that need to be 

addressed. A meeting of stakeholders (Edwards et al. 2013; Lombardo et al. 2010), which included 

meteorologists, wind engineers, and other relevant science and policy disciplines, was convened in 2010 

to discuss these issues and set a direction for the future of the EF Scale. Attendees discussed further 

refinement of the damage/wind speed relationship due to the complexity of both tornado dynamics and 

structural resistance. In addition, they noted that the availability of well–trained surveyors is inadequate, 

especially in major events when NWS offices are extremely busy dealing with multiple storms and 

sometimes multiple tornadoes from the same event. Attendees also mentioned the ambiguity of the QRT 

process as a difficulty in assigning reliable ratings using the EF Scale, discussed the need to revise and 

add DIs, and called for a more rigorous scientific and engineering process for determining the EF rating 

for each event surveyed. Recently, Prevatt et al. (2012) stated that surrounding obstacles and debris 

effects need to be considered. 

That the current EF Scale lacks adequate DIs for distinguishing tornadoes on the upper end of the scale 

was evidenced in the Joplin tornado by the fact that indicators not in the EF Scale (e.g., tractor–trailers, 

manhole covers) were used as supplementary information in making the final EF–5 designation by the 

NWS. In fact, there are only five DIs that, upon reaching a sufficient DOD, indicate an EF–5 status, 

given an expected value of wind speed. The addition of both DI and DOD information at the upper end 

of the EF Scale should be a priority. 

74 NOAA (www.nws.noaa.gov/directives/sym/pd01016004curr.pdf). 

75 NOAA (http://www.noaanews.noaa.gov/stories2007/s2855.htm). 

76 NOAA (www.crh.noaa.gov/Image/dmx/ParkersburgSvcAssmntfinal.pd). 

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2.6 SUMMARY 

2.6.1 Meteorological Conditions 

Based on pre–storm meteorological information, the environment near Joplin was favorable for the 

development of tornadic thunderstorms. This environment was well forecast and anticipated by the NWS 

Storm Prediction Center. Tornado watches were issued over 4 hours before the tornado, and tornado 

warnings based on NWS radar information supplied a minimum lead time of 17 minutes for residents of 

Joplin. Although NWS radar correctly identified a possible tornado, the nearest radars were located a 

significant distance away from Joplin (about 100 km). This distance precluded any information regarding 

the near–surface wind field in and around the Joplin tornado. The tornado was on the ground in the city 

of Joplin for a time period of approximately 15 minutes. 

2.6.2 Near–Surface Wind Environment 

As no radar information was available on near–surface wind speeds, other methods were used to estimate 

the near–surface wind environment. Directly measured wind speed estimates were limited to those 

captured by a weather station at the Joplin Airport (KJLN). Although 5 miles to 6 miles away from the 

heaviest damage in the tornado, KJLN recorded sustained (2 minute) wind speeds of over 40 mph and 

gusts (3 s) over 50 mph. These wind speed magnitudes, coupled with wind directions that were 

coincident with the tornado position, suggest that the winds at the KJLN location were affected by the 

mesocyclone of the thunderstorm that produced the Joplin tornado for approximately 15 minutes. 

However, because no direct measurements were available within the damaged areas, indirect methods of 

estimating the near–surface wind environment were also developed. 

The EF Scale was used to rate both selected damaged structures surveyed by NIST and a random 

sampling of the approximately 7,400 residential structures that were damaged. Wind speeds based on 

damage to selected NIST–surveyed structures were estimated to range from 140 mph ± 15 mph to 150 

mph ± 15 mph (125 mph to 165 mph). NIST–estimated EF numbers and associated wind speed values 

for these structures were compared to those estimated by experienced researchers and practitioners and by 

other government agencies; variability was found in the degrees of damage, wind speeds, and eventual EF 

ratings. Residential structures in Joplin were given a general damage classification (light, medium, 

heavy/totaled, demolished) based on pre– and post–storm aerial photos. A random sample of 10 

residential structures within each damage class was subjected to the EF–Scale procedure. On average, the 

four damage states corresponded to EF–0 (78 mph), EF–1 (93 mph), EF–2 (117 mph), and EF–3 (144 

mph) damage, respectively, with a maximum EF–based estimated wind speed of 175 mph, among the 40 

residential structures surveyed. 

In addition to the EF–Scale estimation, thousands of trees felled in Joplin by the tornado provided the 

opportunity to estimate wind speed by “fitting” a Rankine vortex model to the locations and directions of 

observed tree fall. A citywide grid was created to enable estimation of wind speed and direction as well 

as to create outputs that could be compared with observed tree fall. The Rankine vortex model was 

parameterized using full factorial design with plausible ranges of input parameters estimated from 

damage in Joplin and from previous tornado studies. These ranges were narrowed by comparing the 

model outputs with observed values for parameters such as damage width, damage ratio, and tree fall 

70 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

angle using interaction effect plots. The narrowed parameter ranges were then used as final values in the 

Rankine vortex model and provided uncertainty bounds for the final wind speed estimation. 

Damage width (DW) of tree fall in the Joplin area was up to 1 mile (about 1,600 m) and was generally 

above 0.9 miles (about 1,450 m). This width is in accordance with the estimate of tornado width issued 

by the NWS office in Springfield. The damage ratio (DR) generally ranged from 2.0 to 2.3. 

The radius of maximum wind (RMW) based on tree fall analysis was estimated to range from 0.07 miles 

(113 m, 370 ft) to possibly a maximum of approximately 0.18 miles (290 m, 950 ft) with the average 

estimated value being 0.16 miles (258 m, 845 ft). These RMW values are within the radar–measured 

ranges of other violent tornadoes. The values of alpha (α) were estimated to range from 15 degrees to 25 

degrees. This implies a significant radial component to the flow in the near surface (i.e., purely radial 

flow, α = 0 degrees) as opposed to a purely tangential flow (α = 90 degrees) as has been suggested by 

meteorological and engineering–based studies. Phi (φ) values (0.6 to 0.7) were similar to those in other 

observed vortex phenomena, but differed from values traditionally used in engineering– or probabilistic– 

based models. 

Lower values of φ, as well as a relatively slow translation speed and a more radial flow, may have caused 

both a longer duration and larger spatial extent of significant wind speeds. Based on the tree fall best 

estimation, some areas experienced EF–2 wind speeds or greater for over 1 minute, and the majority of 

those areas experienced EF–2 or greater wind speeds for 30 s or more. Approximately 30 percent of the 

tornado–affected area experienced wind speeds of EF–2 or greater, which is greater than the percentage 

estimated by traditional probabilistic–based engineering models. 

Based on the best estimated parameters of the Rankine vortex model, maximum wind speeds based on 

tree fall were estimated to be in general 175 mph ± 35 mph throughout the areas of highest damage in 

Joplin, suggesting that the tornado maintained its intensity during its time in the city. However, because 

tree fall, like other indirect methods, relies on an indicator (i.e., presence of trees) to estimate wind speed, 

it is entirely possible that maximum wind speeds were above the values provided in this report. The 

maximum wind speeds estimated by tree fall for specific structures surveyed by NIST were similar to the 

wind speeds estimated by EF–Scale methods; however, a wider range was displayed due to the larger 

spatial extent of some of these structures (e.g., Walmart), which can be incorporated by the Rankine 

model. 

Tree fall and aerial damage patterns also seemed to suggest that the tornado underwent considerable 

directional changes over the course of its path through Joplin, and that five to six vortices were present in 

the earlier stages of the tornado. Although analyzing tree fall was extremely helpful in determining the 

near–surface wind field, additional study is needed on this topic and on other indirect estimations of wind 

speed. 

2.6.3 Description of the U.S. Tornado Hazard 

Current methodologies for assessing tornado hazard using “point–based” estimations for probability of 

occurrence in the United States were discussed. Point–based tornado hazard estimations use a 

conditional, areal probability approach that takes into account both tornado strike probability and the 

probability of wind speed exceeding a certain threshold. Information discovered in the Joplin tornado and 

NIST NCSTAR 3, Joplin Tornado Investigation 71 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 2 

in other recent tornado events involving populated areas suggests that “point–based” (i.e., tornado area– 

based) estimation of the tornado hazard may need to be reevaluated. This information includes actual 

damage probabilities that were higher than those derived through EF Scale and tornado wind field 

estimations. 

As an alternative to point–based approximations, a spatially based approach was demonstrated for the 

United States based on a regional tornado rate developed from the NOAA database and the areas (sizes) 

of particular locations, including cities. As nearly all human and economic losses from tornadoes were 

attributed to EF–2 or greater tornadoes based on the NOAA database, the subset of EF–2 or stronger 

tornadoes was examined in the spatially based approach. The areas of particular locations were used 

instead of the tornado–affected areas used in previous point–based climatology. For larger areas, such as 

those in large cities, the spatially based approach produces a probable rate of EF–2 or greater tornado 

strikes that is significantly higher than what is considered in traditional point–based estimations as has 

been corroborated in earlier tornado hazard studies. As urban areas continue to increase in size and 

population, the risk from tornadoes in a spatially based framework also increases. 

2.6.4 Enhanced Fujita Scale Assessment 

Current practice and guidance associated with the EF Scale was discussed, especially for violent 

tornadoes (greater than EF–3). If a tornado is suspected of producing greater than EF–3 damage, causes 

numerous fatalities and catastrophic damage, and is of scientific interest, official NWS guidance states 

that local NWS offices may request the deployment of an NWS Quick Response Team, or QRT. These 

teams are groups of wind damage experts from around the country who, if deployed, have input into the 

final EF rating. A QRT was not deployed in the Joplin tornado; however, they have been used in recent 

violent tornado events such as those in Greensburg, Kansas, Parkersburg, Iowa, and Tuscaloosa, 

Alabama. 

The research described in Sec. 2.5 and other research that has been conducted outside of NIST both 

suggest that further procedural and scientific improvements need to be made to the EF Scale itself. 

Specifically, the current EF Scale lacks adequate damage indicators, especially for distinguishing 

tornadoes at the higher end of the scale. No guidance is provided in the EF Scale for rating of large 

buildings having significant variations of damage as described in Sec 2.3.4.1, leading to ambiguity in the 

assignment of EF numbers. 

72 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

2.7 

Chapter 2 

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Potvin, C. K., A. Shapiro, T. Yu, J. Gao, and M. Xue. 2009. Using a low–order model to detect and 

characterize tornadoes in multiple–Doppler radar data. Monthly Weather Review, 137, 1230–1249. 

Prevatt, D. O., D. B. Roueche, J. W. Van DeLindt, S. Pei, T. Dao, B. Coulbourne, A. Graettinger, R. 

Gupta, and D. Grau. 2012. Building damage observations and EF classifications from the 

Tuscaloosa, AL and Joplin, MO tornadoes. Proceedings of the 43rd ASCE/SEI Structures Congress. 

Chicago, IL, March 29–31. 

Reinhold, T. and B. Ellingwood. 1982. Tornado Damage Risk Assessment. NUREG/CR–2944. 

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Roueche, D. B., and D. O. Prevatt. 2013. Residential damage patterns following the 2011 Tuscaloosa, 

AL and Joplin, MO tornadoes. Proceedings of the 1st Annual Residential Building Design and 

Construction Conference. Bethlehem, PA, February 20–21. 

Silverman, B. W. 1986. Density Estimation for Statistics and Data Analysis. Chapman and Hall. 

Speheger, D. A., C. A. Doswell III, and G. J. Stumpf. 2002. The tornadoes of 3 May 1999: Event 

verification in central Oklahoma and related issues. Weather and Forecasting, 17, 362–381. 

TTU (Texas Tech University). 2006. A Recommendation for an Enhanced Fujita Scale. Available online 

at http://www.depts.ttu.edu/nwi/pubs/FScale/EFScale.pdf, 111 pp. 

Twisdale, L.A. and W.L. Dunn. 1983. Probabilistic analysis of tornado wind risks. Journal of Structural 

Engineering, 109, 468–488. 

Van de Lindt, J. W., S. Pei, T. Dao, A. Graettinger, D. O. Prevatt, R. Gupta, and W. Coulbourne. 2013. 

Dual–objective–based tornado design philosophy. Journal of Structural Engineering, 139, 251–263. 

Verbout, S. M., H. E. Brooks, L. M. Leslie, and D. M. Schultz. 2006. Evolution of the US tornado 

database: 1954–2003. Weather and Forecasting, 21, 86–93. 

Wood, V. T., and R. A. Brown. 2011. Simulated tornadic vortex signature of tornado–like vortices 

having one and two–celled structures. Journal of Applied Meteorology and Climatology, 50, 2338– 

2342. 

Wurman, J., and C. R. Alexander. 2005. The 30 May 1998 Spencer, South Dakota, storm. Part II: 

Comparison of observed damage and radar–derived winds in the tornadoes. Monthly Weather 

Review, 133, 97–119. 

Wurman, J., and S. Gill. 2000. Fine–scale radar observations of the Dimmitt, Texas tornado. Monthly 

Weather Review, 128, 2135–2164. 

Wurman, J., C. Alexander, P. Robinson, and Y. Richardson. 2007. Low–level winds in tornadoes and 

potential catastrophic impacts in urban areas. Bulletin of the American Meteorological Society, 88, 

31–46. 

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Chapter 3 

PERFORMANCE OF BUILDINGS, DESIGNATED SAFE AREAS, AND 

LIFELINES
	

3.1 INTRODUCTION 

3.1.1 Overall Extent of Damage 

The May 22, 2011, Joplin tornado affected thousands of residential, commercial, and institutional 

facilities in Jasper and Newton Counties in Missouri. According to fact sheets from the Joplin Area 

77	 78 Chamber of Commerce (May 1, 2012) and the City of Joplin (May 14, 2012), and to the May 22, 

2012, Joplin Community Press Kit,79 the City of Joplin alone—which bore the brunt of the tornado 

damage—had a total of 553 businesses that sustained severe damage and just over 7,400 residential 

buildings that were damaged to some degree (about 43 percent, or 3,181, of these residential buildings 

were considered destroyed, i.e., structures with a damage classification of heavy/totaled or demolished). 

A general breakdown of affected facilities and buildings based on their functions, derived from the above 

sources and NIST’s analysis of Pictometry® damage data, indicates the following: 

	 One of the two major hospitals, St. John’s Regional Medical Center was damaged severely. 

The other hospital, Freeman Health System, was unaffected. 

	 Ten public and several parochial schools. Those that sustained severe damage and 

building collapses included Joplin High School, Joplin East Middle School, Franklin 

Technology Center, Irving Elementary School, St. Mary’s Catholic Elementary School, and 

Emerson Elementary School. Those damaged less severely included Cecil Floyd Elementary 

School, Duquesne Elementary School, Kelsey Norman Elementary School, and the Roi S. 

Wood Administration Building. 

	 Twenty–eight churches, which suffered varying degrees of damage. 

	 Two fire stations (No. 2 and No. 4) with partial loss of roof. 

	 A large number of commercial facilities, including high–occupancy and smaller buildings 

(big–box stores, medical/dental offices, banks, etc.). 

	 7,411 residential buildings (all were single homes and apartment buildings). Data 

compiled by the Missouri Housing Development Commission80 indicated that about half of 

the areas within the tornado damage path had high concentrations of rental properties (i.e., 42 

percent to 68 percent of the households rented their homes), and the other half had somewhat 

77 http://regionalpartnership.contros.com/JACC%20Fact%20Sheet%205-1-12.pdf. 78 www.joplintornadoanniversary.com/resources/city-of-joplin-factsheet5-14-12.pdf. 79 www.joplintornadoanniversary.com/resources/community-press-kit.pdf. 80 www.mhdc.com/notices/tda/documents/Joplin_Data.pdf. 

NIST NCSTAR 3, Joplin Tornado Investigation 77 
 

 

 

 

 

 

 

 

 

 

 

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lower rental property concentrations (13 percent to 42 percent of households rented their 

homes). This suggested that, of the 20,820 people living in the affected area (41 percent of 

Joplin’s population of 50,175 based on 2010 U.S. Census data81), many resided in rental units 

(an August 6, 2011, article in the Joplin Globe82 put the number of rental units destroyed at 

4,600). In general, this portion of the population was more vulnerable to tornadoes, as they 

largely depended on apartment construction for protection and did not have the ability to 

construct their own shelters. 

In terms of economic loss, the May 14, 2012, City of Joplin fact sheet,2 quoting data provided by the 

Missouri Department of Insurance, Financial Institutions, and Professional Registration, put the insured 

losses incurred by commercial property owners at $1.228 billion and residential property owners at 

$0.552 billion as of April 30, 2012 (with most expected claims received). Thus, losses from building 

damage alone, not counting damage to automobiles and other property, totaled about $1.78 billion by 

April 30, 2012. 

While many of the affected buildings did not collapse, there were many occupants killed or injured by the 

tornado. Table 3–1 provides a brief summary of the building–related fatalities and property loss incurred 

in the Joplin tornado. In–depth analysis of the circumstances and factors surrounding the fatalities and 

injuries is provided in Chapter 4 of this report. 

Table 3–1. Summary of building–related losses from the Joplin tornado. 

Residential 7,411 

Buildings Damaged 

Non–Residential 553 

Total 161 

Fatalities All Building–Related 135 (of 161, or 83.8% of total fatalities) 

Residential Building 

Related 80 (of 135, or 59% of building–related fatalities) 

Residential Property $0.552 billion 

Insured Losses 

(as of April 30, 2012) Commercial Property $1.228 billion 

Besides the damage to facilities, the tornado also caused significant damage to lifeline systems 

(electricity, water, and gas) in the affected areas, including those pertaining to:83 

81 www.census.gov/newsroom/emergencies/2011_tornadoes.html. 82 “Tornado poses questions about putting shelters in apartment buildings” Wally Kennedy, The Joplin Globe, Joplin, MO. August 6, 

2011 

83 www.joplintornadoanniversary.com/resources/community-press-kit.pdf. 

78 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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	 Electricity— 

There was severe damage to the regional electrical transmission and distribution 

infrastructure (high–voltage lines, towers, poles, and substations controlled by Empire 

District Electric) as well as to in–facility distribution systems (lines and fixtures controlled 

and used within individual buildings), resulting in a loss of electrical power for about 20,000 

customers immediately after the May 22, 2011 tornado. Specific tornado impacts included 

two step–down substations damaged and one completely destroyed; approximately 4,000 

distribution poles and transmission towers damaged; roughly 1,500 transformers damaged; 

and about 110 miles of transmission/distribution lines downed. 

	 Water— 

Numerous service lines were broken and leaked water throughout the disaster area. 

The damage included about 4,000 leaking service lines and 25 broken fire–service lines, 

which caused a drastic decrease in water pressure and loss of water from two elevated storage 

tanks within 2 hours after the tornado struck. 

	 Gas— 

Approximately 3,500 gas meters and 55,000 ft of gas main were damaged, affecting 3,500 

customers. 

The sections that follow review building codes and standards issues pertaining to tornado–resistant design 

and the City of Joplin’s code adoptions prior to the tornado. This provides context for the ensuing 

analysis of the performance of different types of buildings that were affected by the May 22, 2011, Joplin 

tornado, the areas of refuge within them, and the lifeline systems related to their operation. 

3.1.2 Scope of Structures Surveyed and Scope of this Chapter 

During field deployments following the May 22, 2011, Joplin tornado, NIST selected 25 structures, out of 

the 7,964 damaged residential and non–residential buildings, for on–site surveys of their performance 

during the tornado. The selected structures included institutional, commercial, and residential buildings 

that were representative of typical construction types, building functions, and levels of damage in the 

affected area. The construction types represented included steel moment resisting frame,84 steel braced 

frame, concrete moment resisting frame, box–type system (BTS) 85 with concrete masonry unit (CMU) 

wall, BTS with precast tilt–up concrete wall, light steel frame, unreinforced brick, and wood frame. By 

function, the surveyed buildings included critical facilities such as a hospital, schools, and fire and police 

stations; high–occupancy facilities such as large retail stores and churches; smaller medical and 

commercial offices; as well as a nursing home and single– and multi–family residences. Besides 

84	 The moment resisting frame system is one of two basic types of lateral load resisting systems commonly used in engineered 

buildings (the other is the box-type system). Some buildings may be designed with a dual system containing both types for a 

more redundant lateral load system. In steel or concrete moment resisting frame, the lateral load resistance is provided primarily 

by the interconnection of floor beams/girders and the columns (through rigid beam-column joints), and the gravity load is provided 

by the floor and roof diaphragms and the columns. 

85	 The box-type system (BTS) is one of two basic types of lateral load resisting systems commonly used in engineered buildings 

(the other is the moment resisting frame system). BTS buildings are buildings with exterior walls (typically made of either CMU or 

precast concrete walls) that form the “box” and provide both gravity and lateral load resistances. However, the stability of the 

exterior walls is critically dependent upon the connection to, and the stiffness of, the roof system (which forms the “lid” of the “box” 

and serves as a diaphragm providing lateral bracing for, and transferring lateral loads, to the exterior walls). 

NIST NCSTAR 3, Joplin Tornado Investigation 79 
 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

buildings, several lifeline facilities were also surveyed, including a power substation, a water treatment 

plant, and structures housing backup generators and chiller equipment for St. John’s Regional Medical 

Center (SJRMC). 

86	 87 Table 3–2 groups the NIST–surveyed buildings into engineered versus non– or marginally engineered

categories and summarizes their damage conditions. Figure 3–1 through 3–3 show the locations of these 

buildings along the tornado damage path. The color coding on these figures depicts the damage 

conditions of these and other buildings, including residential construction, as estimated by Pictometry® . 

Following its field surveys, NIST worked with third parties, including the Joplin Public Works 

Department, relevant building owners (such as the Sisters of Mercy, the parent organization of SJRMC), 

relevant architectural and engineering design firms (Patterson Latimer Jones Brannon Denham (PLJBD) 

and Heery International, Inc.), and the Structural Engineers Association of Kansas and Missouri 

(SEAKM) to obtain design information about the NIST–surveyed buildings. For various reasons (e.g., 

age, damage to records), NIST was unable to obtain complete design information for all of the buildings 

that were surveyed. The last three columns of Table 3–2 summarize the basic design information that 

pertains to the buildings surveyed by NIST, including types of construction, applicable building codes, 

and whether NIST was able to obtain complete, partial, or no design information for the respective 

building. Note that all of the engineered buildings that sustained partial or total structural collapse were 

BTS buildings with either concrete masonry or tilt–up precast concrete perimeter walls. 

This chapter examines the performance of the NIST–surveyed buildings, including designated safe areas 

within these buildings, as well as the performance of lifeline systems that pertain to building operations. 

Chapter 3 includes the following sections: 

	 Section 3.1.3 describes the methodology and technical approach that NIST used in evaluating 

the performance of buildings in this Technical Investigation. 

	 Section 3.1.4 describes current national approaches to tornado design, to provide proper 

context for the effects resulting from the May 22, 2011, Joplin tornado. 

	 Section 3.1.5 summarizes the City of Joplin’s history of adopting building codes. 

	 Section 3.2 describes the performance of the NIST–surveyed buildings (critical facilities and 

high–occupancy buildings in Sec. 3.2.1, commercial buildings in Sec. 3.2.2, and residential 

buildings in Sec. 3.2.3); it includes design and damage information, and in cases where 

structural failures occurred and design information was available, descriptions of possible 

failure hypotheses developed based on the methodology described in Sec. 3.1.3. 

	 Section 3.3 evaluates the performance of designated safe areas found in the surveyed 

buildings (Sections 3.3.1 through 3.3.3) and the performance of individual residential shelters 

(Sec. 3.3.4). 

86 Engineered buildings: Buildings that are designed to satisfy specific design requirements stipulated by building codes through 

use of structural engineering analysis and calculation. 

87 Non- or Marginally engineered buildings: Buildings that are constructed in accordance with prescriptive requirements of the 

building codes but with minimal or no use of structural engineering analysis and calculation. 

80 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

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Chapter 3 

Table 3–2. List of NIST–surveyed buildings with damage condition and design information. 

Damage Condition Design Information 

Collapse of Main Wind Force Resisting 

System (MWFRS) 

Damage/Loss of Roof and/or Wall 

Cladding Loss of Functionality 

Construction 

Type Building Code 

Drawings 

Obtained 

by NIST 

Engineered10 

Walmart Complete BTS (CMU) BOCA 1990/IBC 2000 Complete 

Joplin East Middle School Auditorium Complete BTS (CMU) IBC 2000 Complete 

St. Mary’s School Complete BTS (CMU) BOCA NBC/1990 Partial 

Franklin Technology Center Complete BTS (CMU) BOCA BBC/1978 Partial 

SJRMC Generator and Chiller Buildings Complete BTS (CMU) Not known Partial 

Home Depot Complete BTS (Tilt–up) BOCA NBC/1996 Complete 

Joplin East Middle School Gymnasium Complete BTS (Tilt–up) IBC 2000 Complete 

SJRMC Hospital Buildings Complete CF, SF Not known Partial 

St. Paul’s United Methodist Church Complete SF BOCA NBC/1996 Partial 

Joplin High School Buildings Complete CF, SF IBC 2000 Partial 

Ramesh Shaw Center Complete SF BOCA NBC/1990 Partial 

William Meredith Center Complete SF Not known None 

Ozark Center for Autism Complete CF Not known Partial 

Non

–/Marginally

Engineered11 

Single– and multi–family homes Single– and multi–family homes Complete/Partial/No WF Various years None 

Mercy Village Partial WF IBC 2000 Partial 

Swanson Office Building Partial WF IBC 2006 Complete 

Fire and Police Stations Partial WF Not known None 

Key: BTS, Box–Type System; CF, Concrete Frame; SF, Steel Frame; WF, Wood Frame; CMU, Concrete Masonry Unit; BOCA, Building Officials and Code Administrators 

International, Inc.; NBC, National Building Code; BBC, Basic Building Code; IBC, International Building Code. 

NIST NCSTAR 3, Joplin Tornado Investigation 81 
 

 

 

 

 

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Aerial image © 2011 GeoEye. Building footprint data Pictometry®. Used with permission. Enhancements by NIST. 

Figure 3–1. Westernmost (earliest) segment of the tornado path through Joplin, showing locations of facilities surveyed by 

NIST relative to the estimated center line of the tornado damage path (red solid line). The color coded building footprints 

indicate the estimated level of damage to individual structures (see legend above). 

82 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

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Aerial image © 2011 GeoEye. Building footprint data Pictometry®. Used with permission. Enhancements by NIST. 

Figure 3–2. Central segment of the tornado path through Joplin, showing locations of facilities surveyed by NIST relative to 

the estimated center line of the tornado damage path (red solid line). The color coded building footprints indicate the 

estimated level of damage to individual structures (see legend above). 

NIST NCSTAR 3, Joplin Tornado Investigation 83 
 

 

 

 

 

Chapter 3 

Aerial image © 2011 GeoEye. Building footprint data Pictometry®. Used with permission. Enhancements by NIST. 

Figure 3–3. Easternmost segment of the tornado path through Joplin, showing locations of facilities surveyed by NIST 

relative to the estimated center line of the tornado damage path (red solid line). The color coded building footprints 

indicate the estimated level of damage to individual structures (see legend above). 

84 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

Chapter 3 

	 Section 3.4 describes the effects of the tornado on lifeline systems that pertain to operation of 

buildings in the tornado–affected area. 

	 Section 3.5 lists references cited throughout the chapter 

3.1.3 Methodology for Building Performance Evaluation 

The building performance issues resulting from this tornado are broad in scope, involving many types of 

construction of varying ages, and building designs that are based on successive versions of local building 

codes dating back to the 1960s. These different types of construction, while not designed for tornadoes, 

especially the extreme hazards associated with the May 22, 2011, Joplin tornado, performed very 

differently and sustained significantly different effects in this event. 

Given the variety of structural systems involved, the varying availability of design information, and the 

different levels of building performance observed (both in terms of structural integrity and functionality), 

NIST adopted the methodology described below for evaluating the performance of building and lifeline 

systems in this tornado. The aims were (a) to address issues that pertain to whether the structures were 

designed and constructed in accordance with the applicable building codes, and whether code–level 

design wind loads would have caused the failures observed in some of the structures surveyed by NIST; 

and (b) to identify construction practices that lead to better performance in tornadoes or practices that can 

be improved for the same purpose. 

	 For engineered buildings that sustained structural collapse and for which NIST has complete 

design information: 

	 Use the design information (including design parameters, building dimensions, and 

applicable building codes) to re–create the code–level design wind pressure for the 

building. 

	 Use NIST’s estimation of the wind environment to establish the tornado hazards affecting 

the structure. 

	 Study the observed failures and compute the loads required to cause such failures. 

	 Compare the failure loads with the code–level pressure to determine if the building would 

have sustained the failures under code–level loading. 

	 Identify the sequence of occurrences leading to the failures based on field observations 

and analysis of the strengths of different structural components. 

	 Identify changes to design and construction codes and practices that can potentially lead 

to reduced building vulnerability and improved performance in tornadoes. 

 For engineered buildings that sustained damage to the envelope but did not collapse: 

	 Review any available design information and use data collected in the field as well as 

from third parties to develop an understanding of the structural systems of the building. 

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Chapter 3 

	 Use NIST’s estimation of the wind environment to establish the tornado hazards affecting 

the structure. 

	 Use field–survey damage data and survivor interview information to explain the effects 

of the tornado on building performance, both in terms of physical damage and building 

functionality. 

‒ Identify changes to design and construction codes and practices that can potentially lead 

to reduced vulnerability and improved performance. 

3.1.4 Tornado Design: A National Perspective 

In jurisdictions in the United States that adopt building codes, the majority of the designs of conventional 

88 89 buildings—except for storm shelters, safe rooms, and the safety–related structures, systems, and 

components 90 of nuclear power plants—is governed by the provisions of one of the model building codes, 

such as the International Code Council’s (ICC) International Building Code (ICC 2012a) or International 

Residential Code for One– and Two–Family Dwellings (ICC 2012b), or the National Fire Protection 

Association’s (NFPA) Building Construction and Safety Code (NFPA 2012). These model codes 

typically adopt provisions of the American Society of Civil Engineers ASCE 7 standard (2010) for 

determining minimum loads associated with the hazards (e.g., flood, snow, seismic, wind) considered in 

structural design. 

For the wind hazard, ASCE 7 specifies a basic wind speed for use in determining design wind loads on 

structures in and outside of hurricane–prone regions. ASCE 7 allows the use of regional climatic data for 

estimating the basic wind speeds used in design in lieu of the ASCE–specified values as long as the data 

and data–analysis procedures meet certain statistical requirements. Although the commentary to the 

current ASCE 7 standard provides a tornado hazard map for the contiguous United States (developed in 

the 1980’s and based on a 10 –5 annual exceedance probability), neither ASCE 7 nor the model building 

codes specify tornadoes as a design condition for conventional buildings, or require conventional 

buildings in tornado–prone regions to have occupant shelters at present. Thus, even though the 

requirements for wind–resistant design have been revised through regular updates to the model codes and 

ASCE 7 standard over the years (see summary of most significant changes pertaining to wind design in 

Table 3–3), neither the main wind–force resisting system (MWFRS) nor the components and cladding 

(C&C) of conventional buildings that have been designed to today’s minimum code requirements for 

wind hazard are expected to withstand the combined hazards of extreme wind speeds and wind–borne 

debris impact associated with strong tornadoes. 

For safety–related structures, systems, and components of nuclear power plants, tornadoes are explicitly 

specified as a design condition. The U.S. Nuclear Regulatory Commission (NRC)/Regulatory Guide 

(RG)91 1.76 (1974), Design Basis Tornado and Tornado Missiles for Nuclear Power Plants, defined 

design–basis tornadoes as events with an annual exceedance probability of 10 –7 (a return period of 10 

million years) and prescribed tornado design parameters that include wind speed, pressure drop, and 

88 Structures, either enclosed or partially enclosed in a host building, designed to the ICC 500 Standard.
 89 All stand-alone and internal structures designed to the FEMA 320 and FEMA 361 criteria.
 90 As defined by U.S. Nuclear Regulatory Commission/Regulatory Guide 1.117, Tornado Design Classification.
 91 NRC/RGs are NRC-issued, non-mandatory guides that describe methods and information considered acceptable to the NRC.
 

86 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

Table 3–3. Summary of significant changes in codes and standards pertaining to wind 

design. 

Codes/Standards Changes Pertaining to Wind Resistance Design 

SBC (1982) 

UBC (1982) 

BOCA NBC (1987) 

 Increased required uplift loads at roof perimeter and corners. 

ASCE 7 (1995) 

IBC (2000) 

 Used 3 second gust speed instead of fastest mile for basic design wind speed. Revised 

basic wind speed map from 70 mph fastest mile (approximately 85 mph in 3 second gust 

speed) to 90 mph 3 second gust for most non–hurricane–prone regions (resulting in 

increased basic design wind speed)92 . 

 Included provisions for torsional loading effect on buildings with mean roof height ≥ 60 ft. 

 Increased internal pressure coefficients for partially enclosed buildings and buildings in 

hurricane–prone regions. 

 Updated basic design wind speed map from ASCE 7–9593 

ASCE 7 (1998) 

IBC (2000)  Added requirement for impact–resistant glazing or protection for glazing at heights less 

than 60 ft above ground for Category II, III, and IV buildings in wind–borne debris regions. 

ASCE 7 (2002) 

IBC (2003)  Included provisions for wind loads on parapets and rooftop equipment. 

ASCE 7 (2010)94 

 Changed load factor for wind load to 1.0 from 1.6. 

 Increased design wind speed for Performance Category II buildings to 115 mph 

(corresponding to an increase in wind velocity return period in the central US from 50 to 

700 years). 

 Increased design wind speed for Performance Category III and IV buildings to 120 mph 

(increase in wind velocity return period in the central US from 100 to 1,700 years). 

Key: ASCE, American Society of Civil Engineers; BOCA NBC, Building Officials and Code Administrators National Building Code; 

IBC, International Building Code; SBC, Standard Building Code; UBC, Uniform Building Code. 

wind–borne missile load for three geographic regions. The American National Standards Institute 

(ANSI)/American Nuclear Society (ANS) Standard 2.3 (1983), Standard for Estimating Tornado and 

Extreme Wind Characteristics at Nuclear Power Sites,95 provided similar design parameters, but for a 

range of annual exceedance probabilities between 10 –5 and 10 –7 . Both NRC/RG 1.76 and ANSI/ANS 2.3 

prescribed maximum tornado wind speeds of 320 mph, 250 mph, and 180 mph (in fastest mile) for 

regions I, II, and III, respectively. The recently revised versions of these standards, NRC/RG 1.76 (2007) 

and ANSI/ANS 2.3 (2011), significantly reduced these tornado wind speeds, based on tornado probability 

92 This is the most significant change in ASCE 7-95. However, this change resulted in no net increase in design wind loads for most 

structural systems, except for overhang areas, since terrain and height factors, gust effect factors, and pressure coefficients were 

accordingly adjusted so that loads did not change. 

93 Based on new and more complete analysis of hurricane wind speeds which yields estimations of 50 and 100 year return period 

peak gust wind speeds along the coast. The new wind speed map includes the hurricane importance factor, which varies in 

magnitude and position along the coast and with distance inland, in the basic wind speed contours. 

94 The changes listed here represented no real net change in the design loads for buildings as the increase in design wind speeds is 

balanced by the reduction in load factor. 

95 A voluntary, consensus, industry standard, developed by the ANS and approved by ANSI. 

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studies described in NUREG/CR–4461 (Ramsdell and Rishel 2007) and in a report prepared at Lawrence 

Livermore National Laboratory (Boissonnade 2000), to 230 mph, 200 mph, and 160 mph for the three 

regions (see Fig. 3–4). In addition, the U.S. Department of Energy (DOE) Standard 1020 (2002), Natural 

Phenomena Hazards Design and Evaluation Criteria for Department of Energy Facilities, incorporates 

probability–based wind speeds similar to those in ANSI/ANS 2.3 (2011), but specifies the design tornado 

wind speeds for DOE’s Performance Category 3 and 4 structures as speeds consistent with annual 

exceedance probabilities of 2  10 –5 and 2  10 –6 (50,000–year and 500,000–year return periods), 

respectively. 

ANS 2.3 (2011) Tornado 

Wind Speed by Region: 

(3-second gust at 33 ft) 

Region I: 230 mph 

Region II: 200 mph 

Region III: 160 mph 

Source: Extracted from American National Standard ANSI/ANS-2.3-2011 with permission of the publisher the 

American Nuclear Society. 

Figure 3–4. Regionalization of tornado wind hazard 

Similar to safety–related structures, systems, and components of nuclear power plants, the design of 

tornado shelters and safe rooms also requires explicit consideration of the effects of tornadoes. The 

ICC/National Storm Shelter Association 500 Standard for the Design and Construction of Storm Shelters 

(ICC/NSSA 2008) prescribes the minimum design wind and missile speeds for the design of ICC storm 

shelters. FEMA 320 (2008a), Taking Shelter from the Storm: Building a Safe Room for Your Home or 

Small Business, and FEMA 361 (2008b), Design and Construction Guidance for Community Safe Rooms, 

also provide design requirements and construction guidance for FEMA safe rooms. Both the ICC 500 

standard and the FEMA guides prescribe the same tornado hazard map showing four wind speed zones 

for the contiguous United States with maximum tornado wind speeds of 250 mph, 200 mph, 160 mph, 

and 130 mph (see Fig. 3–5). The wind speed zones in the FEMA guides and ICC 500 were developed 

88 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

Chapter 3 

Source: FEMA (2008). 

Figure 3–5. Tornado hazard map for shelter and safe–room design. 

using tornado data recorded over the 1950–2006 period. It should be noted that there are differences in 

both the regionalization and the wind speeds between the nuclear–related standards (NRC/RG 1.76 

(2007), ANSI/ANS 2.3 (2011), and DOE 1020 (2002)) and the standards/design guides for storm shelters 

and safe rooms (ICC 500 (2008), FEMA 320 (2008), and FEMA 361 (2008)), as shown in Fig. 3–4 and 

3–5. These differences highlight the inconsistency in methodologies for tornado hazard characterization. 

Additional guidance for improving the tornado–resistant design of critical facilities, hospitals, and schools 

is provided in FEMA 543 (2007a), FEMA 577 (2007b), and FEMA P–424 (2010), respectively. 

3.1.5 History of Building Code Adoption in Joplin 

Although the State of Missouri does not presently have an adopted statewide building code, the City of 

Joplin, one of the State’s municipalities, has had a long history of code adoptions, with records dating 

back to 1877 (see Appendix G). Table 3–4 summarizes the building codes and amendments relevant to 

wind design that have been adopted by the City of Joplin since the 1960s. As shown, prior to the May 22, 

2011, Joplin tornado, the most significant adoption of building codes by the City of Joplin took place in 

May 2008, through Ordinance No. 2008–068 (City of Joplin 2008), which adopted the 2006 ICC 

International Building Code (IBC), including Appendix Chapters C, F, G, I, and J, and the 2006 ICC 

International Residential Code for One– and Two–Family Dwellings (IRC), including Appendix Chapters 

A, B, C, D, G, H, I, J, M, N, and Q, with amendments (30 lb/ft2 as the design snow load for roofs). 

NIST NCSTAR 3, Joplin Tornado Investigation 89 
 

 

 

 

 

 

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Table 3–4. History of code adoptions and amendments relevant to wind design by the
 

City of Joplin, Missouri.
 

Required Increased Wind 

Loads for Critical Facilities 

or Increased Resistance for 

Code Adopted (Date) Relevant Amendments Residential Structures 

1960 BOCA BBC (7/1961) Yes 

1965 BOCA BBC (10/1966) Yes 

1970 BOCA BBC (3/1970) Yes 

1978 BOCA BBC (5/1980) Yes 

1984 BOCA B/NBC (7/1984) Yes 

1990 BOCA NBC (11/1990) Ord. 93–6 (snow and wind loads) Yes 

1996 BOCA NBC (7/1997) Yes 

2000 IBC, IRC (3/2003) Yes 

2006 IBC, IRC (5/2008) Ord. 2008–068 (snow and wind loads, roofing 

and exterior finish materials) 

Ord. 2011–142 (residential foundation 

anchorage spacing, truss to wall connection, 

uplift resistance) 

Yes 

Key: BOCA BBC, Building Officials and Code Administrators Basic Building Code; BOCA NBC, Building Officials and Code
 

Administrators National Building Code; BOCA B/NBC, Building Officials and Code Administrators Basic/National Building
 

Code; IBC, International Building Code; IRC, International Residential Code; Ord., Ordinance.
 

Three months after the May 22, 2011 Joplin tornado, the City of Joplin considered Council Bill 2011–024 

in response to issues related to the construction and performance of single– and two–family residential 

structures observed during the May 22, 2011, Joplin tornado. This bill was passed as Ordinance 2011– 

142 in November 2011 (City of Joplin 2011), which amended provisions of the 2006 IRC (adopted by the 

City of Joplin in May 2008, see Table 3–4) in the following areas: 

	 Required anchor bolts for residential foundation anchorage to be spaced not more than 4 ft on 

center (from 6 ft as specified in Sec. R403.1.6 of the 2006 IRC) 

	 Required every truss to be connected to wall plates by approved connectors having a 

resistance to uplift of not less than 175 pounds (779 N) (this amendment was more a 

clarification of than a change to 2006 IRC Sec. R802.10.5) 

	 Required every rafter to be connected to a supporting wall assembly by approved connectors 

(2006 IRC Sec. R802.11.1 required this only for rafters of roof assemblies subjected to wind 

uplift pressures of 20 lb/ft2 (960 Pa) or greater, not for every rafter) 

90 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

3.2 

Chapter 3 

	 Required every masonry foundation wall to have at least one #4 reinforcing bar, spaced no 

more than 4 in. on center, as anchors in the supporting footing under the masonry wall, and 

required the masonry block cells that contain the reinforcing bar to be filled with concrete, 

regardless of the unbalanced backfill height (Sec. R404.1.1 of the 2006 IRC specified anchor 

bolt spacing for masonry foundation walls based on maximum wall height and maximum 

unbalanced backfill height) 

At the time of the May 22, 2011, Joplin tornado, and as is currently the case for many municipalities in 

tornado–prone areas of the Midwest, the City of Joplin encouraged, but did not mandate, the construction 

of safe rooms in residential (single–family homes and apartments) and commercial buildings. 

PERFORMANCE OF BUILDINGS 

Although conventional buildings are currently not required to be designed for tornadoes, understanding 

how tornado hazards affect and damage buildings that are code–compliant enables evaluation of the 

effectiveness of the tornado resistance of different construction types and building codes, which can result 

in improved future design requirements, more tornado–resilient construction techniques, and ultimately 

improved safety for building occupants. Such understanding can be achieved by studying the 

performance of buildings impacted by tornadoes, through documentation and analysis of the damage they 

sustained and by correlating this observed damage with estimations of the environmental conditions (i.e., 

wind speeds and EF–scale ratings, which are discussed in Chapter 2) they were subjected to during the 

tornado. 

Most buildings in the area affected by the May 22, 2011, Joplin tornado were subjected to wind speeds 

(estimated in Chapter 2) that well exceeded the non–tornadic wind design requirements of the building 

codes applicable to them and impacts from wind–borne debris. The buildings that were surveyed by the 

NIST Team also experienced beyond–code loading conditions and represented typical construction types 

found throughout the United States. These types include steel moment resisting frame (SF), steel braced 

frame, concrete moment resisting frame (CF), concrete shear wall, BTS with CMU wall, BTS with 

precast concrete tilt–up wall, light steel frame, unreinforced brick, and wood frame. The types of damage 

they sustained are also representative of the damage observed for buildings of similar construction types 

in the affected area. Because of the differences in their functions, which entail different design 

requirements and performance expectations, the NIST–surveyed buildings were grouped into the 

following three categories for the performance reviews and damage summaries provided in this chapter: 

	 Critical Facilities and High–Occupancy Buildings (Sec. 3.2.1): These are engineered 

structures with a designated Risk (or Performance or Occupancy) Category of either III or IV 

for structural design purposes (ASCE/SEI 7–10; 2009 IBC; 2009 ICC Performance Code). 

The critical facilities in this section are buildings with Risk Category IV designations 

(referred to as essential facilities in the above references and defined as “buildings and other 

structures that are intended to remain operational in the event of extreme environmental 

loading from flood, wind, snow, or earthquakes”). They include buildings in SJRMC as well 

as Joplin Fire Station #4 and the Duquesne Police Station. The high–occupancy buildings in 

this section have Risk Category III designations; they include Joplin High School, Joplin East 

Middle School, Home Depot, Walmart, St. Mary’s Catholic Elementary School, and the 

Franklin Technology Center. 

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	 Commercial Buildings (Sec. 3.2.2): The structures in this section are engineered buildings 

that can be classified under Risk (or Performance or Occupancy) Category II for structural 

design purposes (ASCE/SEI 7–10; 2009 IBC; 2009 ICC Performance Code). They include 

the Ozark Center for Autism, the William Meredith Center, the Ramesh Shaw Center, and St. 

Paul’s United Methodist Church. 

	 Residential Buildings (Sec. 3.2.3): This section focuses on both multi– and single–family 

dwellings, typically of wood frame construction. Of the approximately 7,400 residential 

buildings in the city of Joplin that were damaged by the tornado, about 43 percent were built 

before 1950, and more than 82 percent were built prior to 1980. Depending on their 

proximity to the tornado center line, these residential buildings sustained damage ranging 

from light to total demolition. 

3.2.1 Critical Facilities and High–Occupancy Buildings 

3.2.1.1 St. John’s Regional Medical Center 

Overview—

SJRMC was located just south of the tornado track, with its northernmost edge approximately 300 ft from 

the estimated center line of the May 22, 2011, Joplin tornado. The medical center comprised two separate 

building complexes aligned in a north–south direction perpendicular to the tornado track (see Figure 3–6). 

The north complex included five buildings: the West Tower (building #1 on Fig. 3–6); the East (Patient) 

Tower (building #2); the Emergency Generator Building (building #3); the Chiller Plant (building #4); 

and the Oncology Clinic building (building #5). These buildings had different structural systems and 

were constructed at different times. The West Tower was the hospital’s original building, constructed in 

1965 in the first phase of construction. The East Tower and Oncology Clinic were subsequently added in 

1982 in the second construction phase. The East and West Towers were the tallest buildings in the 

immediate area. The towers and the Oncology building were linked by three–story concrete frame 

sections, which were added in the third construction phase in 1990 and formed a common base joining 

most buildings of the north complex. These sections were designed based on the Building Officials and 

Code Administrators (BOCA) Basic/National Building Code (B/NBC) of 1984. 

The south complex included three buildings: Medical Office Building (MOB) 1 (building #6 on Figure 3– 

6), MOB 2 (building #7), and the Physician’s Office Building (building #8). Each of these buildings was 

an independent steel–frame structure. 

The SJRMC buildings were color–coded on Fig. 3–6 based on damage estimates by Pictometry® which 

showed the Emergency Generator Building as being demolished by the tornado and all other SJRMC 

buildings as having sustained medium damage. The Pictometry® database was one of three damage 

92 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

Chapter 3
 

Damage Key 

Demolished 

Heavy/Totaled 

Medium 

Light 

North Complex 

South 

Complex 

6 

7 

8 

1 

2 

3 

4 

5 

1 

2 

5 

SJRMC North Complex 

8 

7 

6 

SJRMC South Complex 

3 

4 

Aerial image © 2011 GeoEye. Building footprint data Pictometry®. Used with permission. Enhancements by NIST. 

Figure 3–6. Overview of St. John’s Regional Medical Center. 

Key Plan 

(1) West Tower 

(2) East Tower 

(3) Emergency Generator Bldg 

(4) Chiller Plant 

(5) Oncology Clinic Building 

(6) Medical Office Building 1 

(7) Medical Office Building 2 

(8) Physician’s Office Building 

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Chapter 3 

databases obtained by NIST (the others created by the U.S. Army Corps of Engineers and the SAVE96 

Coalition). SJRMC was situated immediately to the east of a mixed commercial and residential area in 

which the majority of buildings were demolished by the tornado (EF–4 damage based on NIST’s 

evaluation). Thus, it was directly downstream of the debris field that resulted from the damage to 

buildings in this area. 

Figures 3–7 and 3–8 show the time histories of wind speed and wind direction estimated for locations 

close to the north and south complexes of SJRMC. These figures indicate that buildings in the north 

complex, which were closer to the center line of the tornado damage path, experienced stronger winds 

than did buildings in the south complex. The maximum wind speed that affected buildings in the north 

complex was estimated to be about 170 mph ± 45 mph (EF–4 range, from a westerly direction), and the 

maximum wind speed affecting the south complex buildings was estimated to be about 120 mph ± 40 

mph (EF–2 range, from a south–westerly direction). Given SJRMC’s functionality as a critical facility 

that should remain operational, current building code would have designated its buildings as Risk 

Category IV structures for design purposes, meaning that they should have been able to withstand 120 

mph wind speed based on today’s design standards. 

The tornado caused 14 fatalities at SJRMC (5 on the day of the tornado, 4 who were Intensive Care Unit 

(ICU) patients on respirators and 1 who was on the 3rd floor, plus 9 who were injured that day and died 

later—see Chapter 4). At the time the tornado struck, there were reportedly 183 patients at the hospital. 

Most of these patients (except those in the ICU) were moved to the hallway areas on each floor of the 

buildings following the tornado warnings, according to SJRMC’s staff. 

NIST received a significant amount of information on the design and construction of, and the damage 

sustained by, buildings at SJRMC from the Joplin Public Works Department, Sisters of Mercy (parent 

organization of SJRMC), and architectural and engineering design firms contracted by Sisters of Mercy. 

However, despite timely and full cooperation from all of these organizations, NIST was only able to 

obtain partial drawing sets for the SJRMC buildings. This is due primarily to the loss of records due to 

the passage of time (the first building was designed in 1965). The following important documents and 

materials were not located for SJRMC buildings: 

	 Structural drawings and specifications and as–built drawings for most buildings and additions 

at SJRMC, including the West Tower. 

	 Drawings and specifications for renovations that involved the modification or replacement of 

windows, particularly the 1969 renovations to the Behavioral Health Unit on the fifth floor of 

the West Tower. The windows in this unit are believed to have been breakage resistant and 

appeared to sustain much less damage compared with other windows at SJRMC. 

Information about the performance of individual buildings at SJRMC during the May 22, 2011, Joplin 

tornado—developed based on damage observations, estimation of the environmental conditions that 

affected the buildings, and available design information—is summarized below. 

96 Structural Assessment and Visual Evaluation, a Missouri State Emergency Management Agency volunteer organization of 

architects, engineers, and building inspectors that conducted building evaluations at the request of the City of Joplin following the 

May 22, 2011, tornado. 

94 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

Chapter 3 

Figure 3–7. Estimated time–history of wind speed and 

direction near the north end of SJRMC. 

Figure 3–8. Estimated time–history of wind speed and 

direction near the south end of SJRMC. 

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West Tower—

Figure 3–9 shows the north–facing side of this building. Following is information about the design of the 

building and its performance in the tornado. 

Figure 3–9. SJRMC's West Tower (north side). 

Design Information: 

 Year Built: 1965. 

 Building Code: Actual design information was not available. The design was likely based on 

the 1960 BOCA BBC given the year of construction and the adoption of this code by the City 

of Joplin in July 1961 (see Appendix G). 

	 Design Wind Speed: Actual design information was not available; likely 70 mph (in fastest 

mile,97 or about 85 mph in 3 second gust) given the year of construction and the building code 

then in effect. 

	 MWFRS: Seven–story, cast–in–place reinforced concrete (RC) frame, with a mean roof 

height of 86.7 ft. 

	 Floor System: RC waffle slab floor. 

	 Components and Cladding: 

Prior to the late 1990’s, building codes referenced ‘fastest mile’ wind speeds, which is a measure of a sustained wind speed. 

Subsequently, building codes began referencing peak gust wind speeds. 

96 NIST NCSTAR 3, Joplin Tornado Investigation 

97 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

‒ Envelope: Except for the fifth floor, which housed the Behavioral Health Unit and had 

breakage–resistant glass windows, the rest of the West Tower’s envelope consisted 

predominantly of single–story curtain wall panels made of aluminum framing with either 

(a) dual–pane insulated glass windows (with inner and outer panes separated by a space 

filled with inert gas) or (b) aluminum panels, and a smaller area with brick curtain walls. 

‒ Roof Assembly: Concrete slab covered by (a) single–layer rigid insulation, (b) single– 

ply, loose–laid ethylene propylene diene monomer (EPDM) membrane, and (c) aggregate 

ballast (smooth gravel with a maximum size slightly larger than a golf ball). 

	 Other Features: Two–story penthouse elevator machine rooms. The first story of the 

penthouse (considered the 8th floor of the building), which was accessible by elevator, had a 

cast–in–place RC frame. The second story, accessible by stairs from the first story of the 

penthouse, had a steel frame. 

Damage and Performance Information: 

	 There was no structural damage to either the lateral load system (RC frame MWFRS) or the 

gravity load system (RC waffle floor slabs). 

	 The building envelope sustained significant damage, including: 

‒ Breakage of almost all (up to 80 percent of) vertical glass windows (both panes) and 

damage to vertical aluminum window mullions on all three wind–exposed sides of the 

tower (north, south, and west), except for the breakage–resistant glass windows on the 

fifth floor (see Fig. 3–10 and 3–11). While there was evidence of window breakage by 

small projectiles (general wind–borne debris, including roof gravel, found in building 

interior), the overall damage to the windows was likely caused by both wind overpressure 

and the impact of wind–borne debris. Breaches in the building envelope allowed strong 

wind, water, and wind–borne debris to infiltrate and subsequently cause significant 

damage to the interior of the building (see below). 

‒ Breakage of some brick curtain walls. 

‒ Collapse of the unreinforced CMU penthouse’s curtain walls that protected the elevator 

machine rooms (see Fig. 3–12). 

‒ Loss of aggregate ballast from the roof and subsequent peeling–off of the EPDM roofing 

membrane and rigid insulation (also see Fig. 3–12). Note that the current IBC (2012) 

prohibits the use of aggregate as roof ballast for buildings in hurricane–prone regions and 

buildings with mean roof heights exceeding certain heights depending on the required 

basic wind speed and exposure category (see 2012 IBC Sec. 1504.8). In Joplin (90 mph 

basic wind speed and exposure category B), aggregate roof ballast would be prohibited 

for buildings with mean roof heights exceeding 110 ft. Thus, the West Tower, with a 

mean roof height of 86.7 ft, would be in compliance with this current IBC roof aggregate 

requirement. 

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Chapter 3 

Note several intact windows on the fifth floor (Behavioral
 

Health Unit with breakage-resistant windows) compared 

with those of the floors above and below 

Figure 3–10. Intact windows on fifth floor of SJRMC's West Tower (south side). 

Figure 3–11. Intact windows on fifth floor of SJRMC's West Tower (north side). 

98 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

Chapter 3 

Collapsed penthouse 

curtain walls that 

protected elevator 

machine room 

Loss of roof aggregate 

and EPDM membrane 

© 2011 Curtis Lynn Geise. Used with permission. 

Figure 3–12. Damage to roof and penthouse walls of SJRMC's West Tower. 

	 There was significant damage to the building interior, including: 

‒ Breakage or collapse of interior partitions, suspended ceiling systems (hanging grid and 

lay–in ceiling tiles), furniture, electrical fixtures and wiring, HVAC ductwork and 

equipment, and other general building contents (see Fig. 3–13); and 

‒ Infiltration of water and debris, and dislodging of building hazardous materials (asbestos 

on flooring material) (FM Global 2011). 

	 Even if electrical power had not been lost (see “Emergency Generator Building” below), the 

damage to the building envelope and interior would have resulted in the complete loss of 

functionality that occurred in this building. This is because even though there was no damage 

to the structural system, there was a complete loss of control over the interior environment 

(loss of temperature and moisture control due to the breached envelope and damage to HVAC 

equipment and ductwork), over illumination (broken electrical fixtures and wiring), and over 

mechanical vertical movement (damage to the elevator shaft gypsum–wall enclosure and 

elevator machine rooms). In addition, interviews of survivors conducted by NIST revealed 

that the damage to the building envelope and interior also presented the building occupants 

with significant hazards such as tripping, slipping, and electrocution (broken power lines and 

electrical fixtures that might have been energized if backup power had been switched 

NIST NCSTAR 3, Joplin Tornado Investigation 99 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

© 2011 Kermit Bright, P.E.. Used with Permission. 

Figure 3–13. Typical damage to the interior of SJRMC's West Tower. 

automatically) hazards as they tried to evacuate the building in total darkness. Below are 

relevant excerpts from the interview transcripts compiled by NIST: 

“You know what was scary is we were still ankle–deep in water; it was
 

just pouring down like a sieve. The water around our ankles just never
 

went anywhere. It was ankle–deep, and it was sparks over our head, and
 

everybody was worried”. (NIST Interview 2)
	

“Most of us had abrasions and cuts and that sort of thing but no one
 

expired and it’s an absolute miracle. Mostly because the fourth wall in
 

from the outside, from the south part of the hospital stayed up. So the
 

exterior window walls came in, the inside patient room walls came in
 

and another interior wall came down part way and the fourth wall stayed
 

up and that sort of sheltered the interior hallway where we were”. (NIST
	

Interview 6)
 

“And so that was really, really the most difficult thing about that was
 

getting people out once we got them uncovered because there was debris
 

on top of people, on top of us, walls in, doors in, door frames in, debris
 

everywhere. You can’t imagine the shattering that goes on when you 

have materials exposed to that kind of wind. Plus just the wires that 

were down from the ceiling, all the equipment that’s inside a room, 

100 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

debris a foot, two–feet deep some places that you had to move before 

you could get somebody out. And then you had a couple of people who 

had walls on top of them, meaning leaning over them, they were 

compressed under them. Some people—two of them were underneath 

one of those two–inch or inch–and–a–half water mains that I told you 

about for fire suppression. It was falling right on them; they were gonna 

be hypothermic pretty quickly so we had to move them. One of those 

was trapped and it took me probably 15 minutes, 10 minutes, to get her 

loose”. (NIST Interview 6) 

East (Patient) Tower—

The East Tower was connected to the West Tower along its entire elevation by a 10–story steel frame 

(SF) structure that housed the elevator shafts serving both towers. This connecting elevator tower was the 

tallest structure at SJRMC with a 126.8 ft mean roof height. Thus, even though they were independent 

structural systems, the two towers had common, connecting interior floor plans. NIST was able to obtain 

partial framing plans for this building, which showed that it was a steel moment frame structure, but no 

design information (building code, design wind speed). Figures 3–14, 3–15, and 3–16 show exterior 

views of this building. Information about the building’s design and damage is summarized below. 

Design Information: 

	 Year Built: 1985. 

	 Building Code: Actual design information was not available. The design was likely based on 

the 1984 BOCA B/NBC given the year of construction and the adoption of this code by the 

City of Joplin in July 1981 (see Appendix G). 

	 Design Wind Speed: Actual design information was not available. The design wind speed 

was likely 70 mph (in fastest mile, or about 85 mph in 3 second gusts) given the time of 

construction and the building code then in effect. 

	 MWFRS: The East Tower building had a nine–story SF with moment connections and steel 

cross bracing (wind frame, in east–west direction), supported on individual RC spread 

footings with a 109.3 ft mean roof height (just under the 110 ft IBC limit for use of roof 

aggregate). The 10–story elevator tower’s mean roof height was 126.9 ft (above the 110 ft 

IBC limit for use of roof aggregate). 

	 Floor System: Composite concrete–steel deck floor (41⁄2 in. thick semi–lightweight concrete 

slab reinforced with 6  6 W2.1  W2.1 welded wire fabric on 2 in., 18–gauge (0.0474 in. 

thick) wide–rib galvanized steel deck). 

	 Components and Cladding: 

	 Envelope: The East Tower building had a combination of single–story curtain wall 

panels made of aluminum framing and dual–pane insulated glass glazing and a precast 

concrete column–cover–and–spandrel–system. The 10–story elevator tower had a multi– 

story unit–and–mullion with dual–pane insulated glass curtain wall system. 

NIST NCSTAR 3, Joplin Tornado Investigation 101 
 

 

 

 

 

 

 

Chapter 3 

Elevator Tower 

Figure 3–14. View from southwest of SJRMC's East Tower showing that most
 

windows on south and west sides of building and curtain walls
 

on connecting elevator steel frame have broken.
 

Figure 3–15. View from southeast of SJRMC's East Tower showing that most 

windows on south and east sides of building have broken. 

102 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

Chapter 3 

Figure 3–16. Close–up view showing minor damage to architectural 

precast concrete column–cover–and–spandrel system and 

significant damage to glass windows of SJRMC's East Tower. 

	 Roof: Concrete slab covered by single–layer rigid insulation and single–ply, loose–laid 

EPDM membrane with aggregate ballast (same as the West Tower). 

	 Other Features: The East Tower building included a one–story SF penthouse mechanical 

room, accessible by elevators, with vertical insulated metal curtain wall panel cladding. 

Damage and Performance Information: 

	 There was no structural damage to either the lateral load systems (steel moment frame and 

braced frame MWFRS) or the gravity load systems (RC pan joist floor slabs) of the East 

Tower or the connecting elevator tower. 

	 There was significant damage to the building envelope, including: 

	 Breakage, likely caused by both wind pressure and the impact of wind–borne debris 

based on site inspection, of almost all vertical dual–pane insulated glass windows on all 

wind–exposed sides of the East Tower and the glass curtain walls of the 10–story 

connecting elevator tower. 

	 Loss or collapse of the penthouse’s vertical insulated metal curtain wall panels that 

protected the elevator machine/mechanical room (see Fig. 3–17). 

NIST NCSTAR 3, Joplin Tornado Investigation 103 
 

 























 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 


 

Collapsed insulated 

metal curtain wall 

panels 

© 2011 Kermit Bright, P.E.. Used with permission. 

Figure 3–17. Missing/collapsed vertical insulated metal curtain wall 

panels of SJRMC's East Tower penthouse. 

	 Loss of aggregate ballast from the roof and subsequent peeling–off of the roof covering 

system (EPDM roofing membrane and rigid insulation, similar to the West Tower; see 

Figures 3–18 and 3–19). As noted for the West Tower, the nine–story East Tower, with 

its mean roof height of 109.4 ft (just under the IBC limit of 110 ft), was considered code– 

compliant for use of roof aggregate ballast. It is not known if aggregate was used as roof 

ballast for the taller 10–story elevator tower (126.9 ft mean roof height). Regardless of 

the code height limit, there was evidence that the roof aggregate did contribute to the 

damage sustained by the envelopes of adjacent buildings. 

	 There was significant damage to the interior of the East Tower and the connecting elevator 

tower, including damage to the elevator shaft wall. 

Emergency Generator Building— 

This structure was a one–story, above ground, rectangular (28 ft by 48 ft) BTS building with exterior 

CMU walls and a short–span metal roof diaphragm, constructed as part of the third construction phase 

(see Fig. 3–20, 3–21, and 3–22). All other buildings at SJRMC had either steel or concrete frames; the 

Emergency Generator Building was the only BTS building at this facility. 

104 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

Displaced aggregate ballast 

and EPDM roof membrane 

© 2011 Malcolm Carter. Used with permission. 

Figure 3–18. Damage to roof covering system of SJRMC's East Tower (peeling–off
 

of EPDM roof membrane and rigid insulation, loss/displacement of
 

roof aggregate ballast).
 

Design Information: 

 Year Built: 1994. 

 Building Code: BOCA National Building Code/1990. 

 Design Wind Speed: 70 mph (in fastest mile, or about 85 mph in 3 second gusts). 

 MWFRS: This was a one–story BTS building with a 14.5 ft mean roof height and partially 

grouted, lightly reinforced, single–wythe CMU exterior walls (12 in. wide blocks) on RC 

footings. The exterior CMU walls were laterally braced by a wide–rib steel roof deck 

diaphragm supported by single–span, open–web steel bar joists with ends anchored into the 

bond beam (top course of masonry) on top of the exterior CMU walls. 

 Floor System: 5 in. thick RC slab–on–grade. 

 Components and Cladding: 

 Envelope: 12 in. thick CMU walls with 1 in. thick rigid thermal insulation on the exterior 

of the walls. 

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Chapter 3 

West Tower East Tower 

Elevator 

Tower 

Oncology 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 3–19. Overview of West, East, and Elevator Towers and Oncology Clinic Building showing that most of the 

aggregates that were used as roof ballast on these buildings are missing. 

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Chapter 3 

West wall 

North wall 

Figure 3–20. View from northwest of Emergency Generator Building. 

Note northward and eastward direction of wall failure, consistent 

with the direction of maximum wind (westerly) shown on Fig. 3–7. 

East wall 

East wall’s louver

North wall’s 

louver 

Door 

Figure 3–21. East side of Emergency Generator Building. Note eastward
 

direction of failure on east wall (CMU wall falling outward, door opened,
 

louver pushed outward). Also note louver on north wall pushed outward, 

consistent with direction of maximum westerly wind and indicative
 

of high internal pressure.
 

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eam

Chapter 3
 

Roof Joists (ends 

disconnected 

from CMU wall) 

Roof joist with anchor 

pulled from CMU bond 

b 

Broken CMU bond 

beam on top of wall 

Figure 3–22. Failure details at Emergency Generator Building. 

108 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

	 Roof: Single–span, open–web steel bar joists (20K3) at 5 ft spacing, supporting a 11⁄2 in. 

wide–rib metal roof deck that was covered by 2 in. thick rigid thermal insulation boards, 

a layer of single–ply EPDM roof membrane, and aggregate roof ballast. 

	 Other Features: None. 

Damage and Performance Information: 

	 The building sustained total collapse, with damage typical of structural damage associated 

with BTS buildings in extreme wind hazards. The metal roof system (metal deck panels and 

steel bar joists), which provided lateral bracing for the exterior CMU walls, failed 

completely, likely due to wind uplift pressure. Observations made following the tornado 

found that roof deck panels had peeled off from the supporting steel roof trusses (tension 

failure of the puddle welds connecting the roof deck to the bar joists due to wind uplift) and 

the ends of the roof trusses that were anchored into the bond beams on top of the exterior 

walls had disconnected from the walls. All four exterior CMU walls (except for small 

portions of the south and east walls) collapsed. Figures 3–20 and 3–21 show views from the 

northwest and northeast corners of this building, respectively. Note that both the west and 

east walls of the building collapsed eastward, which was the translational direction of the 

tornado and also consistent with the wind direction estimated by wind field model (see 

Chapter 2). Also note that the door and louver on the east wall and the louver on the north 

wall were pushed outward, indicating high internal wind pressure acting on the walls of this 

building. Figure 3–22 shows the reinforcement of the bond beam and the disconnected 

anchor that formerly connected the end of the steel roof truss to the wall. 

	 The total collapse of this building destroyed all of the backup power generators that were 

housed within it, resulting in the loss of the emergency power supply for the entire SJRMC 

complex. 

Chiller Plant—

The Chiller Plant was a one–story steel frame structure located at the northeast corner of the SJRMC’s 

north complex. Being in close proximity to the Emergency Generator Building, it was likely subjected to 

similar wind and debris hazards that affected the Emergency Generator Building. Below is the design and 

performance information that pertains to the Chiller Plant. 

Design Information: 

	 Year Built: 1985. 

	 Building Code: Actual design information was not available. The design was likely based on 

the 1984 BOCA B/NBC given the year of construction and the adoption of this code by the 

City of Joplin in July 1984 (see Appendix G). 

	 Design Wind Speed: Actual design information was not available. The design wind speed 

was likely 70 mph (in fastest mile, or about 85 mph in 3 second gusts) given the time of 

construction and the building code then in effect. 

NIST NCSTAR 3, Joplin Tornado Investigation 109 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

	 MWFRS: Steel frame comprised of W–shape beams and columns that were joined by 

bolted connections. The columns were cast into the concrete foundation. 

	 Floor System: 5 in. thick RC slab. 

	 Components and Cladding: 

	 Envelope: Three–layer exterior wall enclosures comprised of an inner layer of partially 

grouted CMU, a middle layer of extruded polystyrene insulation, and an outer layer of 

brick veneer. 

	 Roof: 11⁄2 in. wide–rib metal roof decks supported by W–shape longitudinal and 

transverse roof beams. 

	 Other Features: None. 

Damage and Performance Information 

	 There was no structural damage to the lateral load resisting system (steel frame MWFRS). 

	 There was significant damage to the building envelope, including: 

	 Loss of some of the roof deck panels and roof covering due to wind uplift (horizontal 

envelope). 

	 Collapse of most of the west wall (directly facing the oncoming tornado), half of the 

north wall, and a smaller portion of the east wall. The south wall was not damaged 

(connected to an adjacent building and was not exposed to wind). These collapses were 

likely the result of debris impacts and lateral wind pressure as the stability of these walls 

did not depend on the lateral bracing by the roof. 

 The damage to the building envelope resulted in the loss of mechanical equipment required 

for air conditioning (evaporator, condenser pumps, and chillers) that was housed inside the 

building, and ultimately the loss of air conditioning for the entire SJRMC even if electrical power 

had not been lost (see Fig. 3–23). 

Oncology Clinic Building—

Design Information: 

 Year Built: 1988. 

 Building Code: BOCA National Building Code/1987. 

 Design Wind Speed: Not specified. The design wind pressures were 22.3 lb/ft2 (0 ft to 20 ft 

height) and 23.8 lb/ft2 (20 ft to 40 ft height). 

	 MWFRS: The clinic building had a two–story SF with moment connections between primary 

members and a mean roof height of 30 ft 71⁄2 in. 

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Collapsed north and west 

walls of Chiller plant 

Reducer gas pipe and valve 

on west wall of Chiller plant 

that was damaged and 

leaked 

Figure 3–23. Views of damage sustained at the Chiller Plant. 

	 Floor System: Composite concrete–steel deck floor (41⁄2 in. thick lightweight concrete slab 

with 6  6, W2  W2 welded wire fabric on 2 in., 18–gauge (0.0474 in. thick) wide–rib 

galvanized steel deck). 

	 Components and Cladding: 

	 Envelope: Single–story curtain wall windows made of aluminum framing with dual– 

pane insulated glass, and precast concrete architectural column and spandrel panels for 

exterior covers. 

NIST NCSTAR 3, Joplin Tornado Investigation 111 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

	 Roof: 11⁄2 in.  6 in., 22–gauge (0.0295 in. thick) wide–rib galvanized steel roof deck, 

covered by 5/8 in. gypsum board, 2 in. thick rigid insulation, single–ply loose–laid 

EPDM roof membrane, and aggregate roof ballast. The steel roof deck was connected to 

the W12  19 wide–flange roof beams (typical) by puddle welds. 

Damage and Performance Information: 

	 There was no structural damage to the lateral load system (steel moment frame MWFRS) or 

the gravity load floor system (composite RC–on–steel deck). 

	 The building envelope sustained significant damage, including: 

	 Breakage of all insulated glass panels and the loss of window systems (glass and 

aluminum frame), likely caused by both wind pressure and the impact of wind–borne 

debris based on site inspection, on all wind–exposed sides of the building (see Fig. 3–24). 

	 Loss of several panels of steel roof deck, roof aggregate, membrane, rigid insulation, and 

gypsum board (see Fig. 3–25 and 3–26). 

The architectural precast column and spandrel covers cladding system sustained only minor 

damage. 

	 There was significant damage to the interior of the building, including: 

	 Breakage or collapse of interior partitions, metal wall studs, suspended ceiling systems 

(hanging grid and lay–in ceiling tiles), furniture, fixtures, and equipment (electrical 

fixtures and wiring, HVAC ductwork, and general building contents) (see Fig. 3–27). 

	 Infiltration of water and debris (including roof aggregate), and dislodging of building 

hazardous materials. 

Medical Office Buildings—

As indicated in Section 3.2.1.1 Overview, the SJRMC’s south complex comprised three independent 

steel–frame structures: Medical Office Building 1; Medical Office Building 2; and Physician’s Office 

Building that served as medical office buildings for the SJRMC (see buildings 6, 7, and 8, respectively, 

on Fig. 36). Being farther south from the estimated tornado damage center line compared with 

SJRMC’s north complex buildings, these medical office buildings were subjected to less severe wind 

speeds, with estimated maximum wind speed of about 120 mph ± 40 mph (EF–2 range, from a 

southwesterly direction, see Fig. 38). The design and performance information pertaining to the medical 

office buildings is summarized in the following section. 

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Broken glass windows 

Missing roof decks 

Source: FEMA Mitigation Assessment Team (MAT) 

Figure 3–24. South elevation 

of Oncology Clinic Building 

showing damage to building 

envelope (broken glass 

windows, missing window 

frame, missing roof decks). 

Missing roof 

decks 

Lost/displaced roof membrane, 

insulation and aggregate ballast 

© 2011 Malcolm Carter. Used with permission. 

Figure 3–25. Roof of 

Oncology Clinic Building: 

missing steel deck panels, 

gypsum board, rigid 

insulation, membrane, and 

aggregate ballast. 

Holes on roof decks where 

puddle welds were torn 

© 2011 Malcolm Carter. Used with permission. 

Figure 3–26. Roof of 

Oncology Clinic Building: 

failed puddle welds 

connecting roof deck with 

supporting roof beam. 

NIST NCSTAR 3, Joplin Tornado Investigation 113 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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© 2011 Malcolm Carter. Used with permission. © 2011 Malcolm Carter. Used with permission. 

Figure 3–27. In Oncology Clinic Building, interior damage to ductwork, electrical wiring, 

suspended ceiling, interior partition/metal stud wall, furniture. Note the aggregate from 

roof in the interior. 

Medical Office Building 1 

This was a two–story steel frame building on a concrete slab foundation. The design and damage 

information is described below. 

Design Information: 

 Year Built: Information was not available. 

 Building Code: Information was not available. 

 Design Wind Speed: Information was not available. 

 MWFRS: Steel frame comprised of W–shape beams and columns that were joined by 

bolted connections. The columns were cast into the concrete foundation. 

 Floor System: Composite concrete–steel deck floor (5 in. thick RC slab). 

 Components and Cladding: 

 Envelope: Comprised of combination of four types of curtain walls: (1) single–story 

glass panels with aluminum framing; (2) brick veneer backed by aluminum stud frames; 

(3) architectural spandrel panels (made of light–gauge steel and aluminum channels and 

cement–based surface boards); and (4) two–story unit–and–mullion walls with glass 

glazing. 

 Roof: 11⁄2 in. wide–rib steel roof decks supported by open–web steel roof joists. 

114 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

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Damage and Performance Information: 

	 There was no structural damage to the MWFRS (steel frame) or the gravity load floor system 

(composite RC–on–steel deck). 

	 The building envelope sustained significant damage, including: 

	 Loss of a large portion of the roof deck (horizontal envelope, see Fig. 3–28; note that all 

of the steel trusses supporting the roof appeared undamaged and connected to the roof 

beams despite the loss of the roof deck) and roof deck covering. 

	 Breakage of almost all glass windows and the loss of several architectural spandrel panels 

(Fig. 3–28). It should also be noted that, despite the breakage of the glass windows, 

there were no failures in the mullion–and–rail system that held the glass panels, or among 

the anchors that connected the system to the structural SF of the building. 

	 In sum, despite there having been no visible damage to the structural frame, the damage 

to the building envelope facilitated further damage to the building’s interior and, as a 

result, rendered this building unusable. 

Missing roof deck 

Broken glass windows, missing 

spandrels, and curtain wall 

Figure 3–28. View of damage to envelope of Medical Office Building 1. 

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Medical Office Building 2 

This was a four–story steel frame building on concrete slab foundation. The design and damage 

information is described below. 

Design Information: 

 Year Built: 1994. 

 Building Code: BOCA National Building Code/1990. 

 Design Wind Speed: 70 mph (in fastest mile, or about 85 mph in 3 second gusts). 

 MWFRS: Steel braced frame system comprised of W–shape beams and columns, joined by 

bolted–and–welded connections, and steel K–braces for lateral load capacity. 

 Floor System: Composite concrete–steel deck floor (41⁄2 in. thick concrete slab on 2 in., 18– 

gauge (0.0474 in. thick) wide–rib galvanized steel deck). 

 Components and Cladding: 

	 Envelope: The building vertical envelope consisted of (a) single–story glass panels with 

aluminum framing, (b) brick veneer backed by aluminum stud frames (on three sides: 

west; north; and south), and (c) architectural spandrel panels made of cement–based 

surface boards and a layer of insulation material, supported by aluminum frames. 

 Roof: 11⁄2 in.  6 in., 22–gauge wide–rib galvanized steel roof deck supported by open– 

web steel roof joists. 

Damage and Performance Information: 

 There was no structural damage to the MWFRS (steel braced frame) or the gravity load floor 

system (composite RC–on–steel deck). 

 The building envelope sustained significant damage, including: 

 Loss of steel roof decks and roof deck covering (horizontal envelope). 

 Breakage of curtain walls on all wind–exposed sides (broken glass windows and loss of 

architectural spandrel panels; see Fig. 3–29, 3–30, and 3–31). 

Physician’s Office Building

This was a two–story steel frame building. The design and damage information is described below. 

Design Information: 

 Year Built: 1988. 

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Broken glass windows 

and spandrels 

Missing 

roof deck 

Bolted beam-column connection 

Broken glass windows, missing 

spandrels, and curtain wall 

Figure 3–29. Views of (top) damage to envelope of Medical Office Building 2 and 

(bottom) portion of the steel frame system (bolted beam–column connection). 

NIST NCSTAR 3, Joplin Tornado Investigation 117 
 

 

 

 

 

 

Chapter 3 

Figure 3–30. Evidence of debris impact causing breakage of windows at
 

Medical Office Building 2.
 

Figure 3–31. Roof aggregate ballast became wind–borne debris (on ground 

by Medical Office Building 2). 

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 Building Code: BOCA National Building Code/1987. 

 Design Wind Speed: Actual design information was not available. The design wind speed 

was likely 70 mph (in fastest mile, or about 85 mph in 3 second gusts) given the time of 

construction and the building code then in effect. 

 MWFRS: Two–story steel frame that comprised of W–shape beams and columns joined by 

bolted–and–welded connections. 

 Floor System: Composite concrete–steel deck floor (41⁄2 in. thick concrete slab on 2 in., 18– 

gauge wide–rib steel deck). 

 Components and Cladding: 

 Envelope: The building vertical envelope consisted of single–story glass panels with 

aluminum framing and architectural metal insulated panels supported by metal studs 

frames. 

 Roof: 11⁄2 in.  6 in., 22–gauge wide–rib galvanized steel roof deck supported by open– 

web steel roof joists. 

Damage and Performance Information: 

 There was no structural damage to the MWFRS (steel frame) or the gravity load floor system 

(composite RC–on–steel deck). 

 The building envelope sustained significant damage, including: 

 Loss of steel roof decks and roof deck covering (horizontal envelope). 

Breakage of curtain walls (broken glass windows and loss of architectural metal panels) and collapse of 

an entire brick veneer curtain wall and the supporting aluminum stud frame on the south–facing wall of 

the building (see Fig. 3–32). 

Figure 3–32. Collapse of an 

entire brick veneer curtain 

wall and the supporting 

aluminum stud frame on the 

south–facing wall of 

Physician’s Office Building. 

NIST NCSTAR 3, Joplin Tornado Investigation 119 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

3.2.1.2 Walmart 

Figures 3–33 and 3–34 show overviews of the partially collapsed Walmart Store 59 at 1501 South Range 

Line Road in Joplin. The store was a one–story, low–rise BTS with a long–span, flexible diaphragm 

metal roof. The building was rectangular in plan, with the long side in the north–south direction and 

perpendicular to the translational direction of the tornado, with approximate dimensions of 573 ft (N–S) 

by 290 ft (E–W), a 21.33 ft mean roof height and a 2 ft parapet. The southernmost end of the building 

was approximately 750 ft north of the estimated center line of the tornado damage path. Estimation of the 

wind speeds affecting the store (see Fig. 3–35 and 3–36) shows a wind speed gradient along the length of 

this building: the uncollapsed north half experienced an estimated maximum wind speed of 110 mph ± 40 

mph (EF–1 to EF–2 range, from a northerly wind direction) and the collapsed south half experienced a 

higher maximum estimated wind speed of 160 mph ± 45 mph (EF–3 to EF–4 range, from a west–

northerly wind direction). Indications that the north half was in a lower wind speed zone also can be seen 

in Fig. 3–33, which shows that areas directly east and west of this portion of the building sustained much 

less damage to structures and vegetation compared with areas further south and closer to the tornado 

center line. The sections below summarize the design, damage, and performance information related to 

this building. 

Design Information: 

	 Year Built: Original design, 1993; remodel, 2007. 

	 Building Codes: Original, BOCA National Building Code/1990; remodel, 2000 IBC. 

	 Design Parameters: 

 Basic Wind Speed: Original design, 85 mph (3 second gusts); remodel, 90 mph (3 

second gusts). 

	 Exposure Category: C. 

	 Importance Factor: 1.15. 

	 Structural System: The structural system comprised three structural components: the roof 

system; a series of steel interior gravity frames; and the perimeter walls. The roof system and 

perimeter walls formed the primary lateral load resistance system (MWFRS), while the 

interior gravity frames and the walls were the primary gravity load resistance system. The 

descriptions of these structural components follow: 

	 Roof System: The structural role of the roof was to (a) support and transfer vertical roof 

loads to the series of individual plane frames, and (b) serve as a structural diaphragm 

providing lateral support for the perimeter walls. The roof system comprised: 

 Steel roof decks: 11⁄2 in.  36 in., 22–gauge (lightest gauge for roof decks, 0.0295 in. 

thick), type B painted wide–rib steel roof decks that were fastened to and supported 

by the trusses described below. 

120 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

Chapter 3
 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 3–33. Aerial views of Walmart in relation to the tornado damage path (red line denotes center of damage path). 

NIST NCSTAR 3, Joplin Tornado Investigation 121 
 

 

 

 

Chapter 3
 

N 

Collapsed 

!rea 

Expansion Joint 

Walmart North Half Walmart South Half 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 3–34. Aerial view of Walmart outlining southern half of building collapsed by the tornado. 

122 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

Chapter 3 

Figure 3–35. Estimated time–history of wind speed and 

direction near the northeast corner of Walmart. 

Figure 3–36. Estimated time–history of wind speed and 

direction near the southeast corner of Walmart. 

NIST NCSTAR 3, Joplin Tornado Investigation 123 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

 Steel roof trusses: K series open–web steel roof joists were typical (except in the 

vestibule area where longer–span LH series joists were used). The connections 

between the roof decks and roof joists were primarily 5/8 in. diameter puddle welds 

in a 36/7 fastener pattern (7 puddle welds across the 36 in. wide steel deck panel). 

Adjacent roof joists were bridged at three points each along the top and bottom 

chords for lateral stability using L11⁄4  11⁄4  1/8 steel angles. Each roof joist was 

additionally braced for uplift resistance by two steel angles, one at each joist end, that 

were field welded (3/16 in. fillet weld) to the joist’s first bottom chord panel points 

and the bottom chord of the supporting joist girder (see description of joist girders 

below). 

	 Interior Gravity Frames: The structural function of these frames was to support and 

transfer vertical loads only from the roof system to the foundation through connections 

with the roof joists. These frames were run in the N–S direction, each with multiple 

spans. Each span consisted of: 

 An open–web steel joist girder that supported the roof joists through field welded 

connections to its top chord (two 3/16 in.  11⁄2 in. fillet welds at each end of the roof 

joist). The joist girder was supported at each end of its top chord by the column and 

base plates described below. 

 A structural steel tube column (TS 8  8  1⁄4 typical interior column). The joist 

girder–to–column connection was a simple shear connection that included two 1⁄4 in. 

 3 in. field fillet welds and two 3⁄4 in. diameter bolts (bottom chord of joist girder 

straddled, but was not connected to, the column’s stabilizer plate). The end columns 

of the frame were embedded into (but not connected to) the perimeter CMU walls. 

 Steel base plates and individual RC square footings supporting the columns. 

	 Perimeter Walls: The structural role of the walls was to support both vertical and lateral 

loads (wind and seismic), with lateral bracing provided by the roof system that acted as a 

horizontal diaphragm. The stability of the perimeter walls was critically dependent upon 

this roof diaphragm action. The perimeter walls comprised 12 in. thick CMU walls (12 

in.  16 in.  8 in. blocks), partially grouted and reinforced with #6 rebar in the vertical 

direction (through the wall’s height) at 4 ft on center (vertical grouting in every sixth cell 

of CMU blocks). The vertical reinforcements extended from the wall bottom into the RC 

spread footing using standard ACI hooks. This wall–to–footing connection by single 

dowels at 4 ft on center provided continuity between the wall and the footing and 

restraint against lateral displacement of the wall (dowel action plus friction), but 

essentially no restraint against wall rotation.98 For continuity in the horizontal direction, 

the top and bottom courses of the CMU walls were also grouted and reinforced 

horizontally with two #5 reinforcing bars to form two continuous bond beams. 

Additional wall continuity was provided by a square structural steel tube link beam (TS 

98	 This is not inconsistent with standard practice. A friction-only connection between wall and footing is accepted for regions with 

low or no seismic risk. The wall’s rotational stability is to be provided by temporary bracing during the construction phase (prior to 

connection to the roof system) and by lateral bracing provided by the roof system after connection with the roof. 

124 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

21⁄2  21⁄2  3/16) welded to steel plates that were anchored into the bond beam at regular 

intervals along the tops of the perimeter walls. 

	 Components and Cladding: 

	 Envelope: CMU exterior, with sliding doors with 1⁄4 in. tempered glass and aluminum 

frames at the north and south entrances on the west wall. 

	 Roof Covering: Rigid insulation on the metal roof deck, covered by roof membrane. 

	 Other Features: An expansion joint cut through the RC floor slab and the east and perimeter 

walls, along the E–W direction at 209.5 ft from the south wall, effectively dividing the 

building into two independent structural subsystems, a north half and a south half. The 

horizontal reinforcements in the bond beams were terminated at this expansion joint. 

Damage and Performance Information: 

	 The MWFRS of the south half of the building (perimeter walls laterally braced by roof 

system) completely collapsed, with: 

	 The entire roof system (roof deck and roof joists) disconnected and either displaced 

upward or was completely blown away from the supporting joist girders and walls 

(evidence of wind uplift action, see Fig. 3–37 and 3–38). 

	 The west and east walls (where the roof system that was supposed to provide lateral 

bracing was lost), and portions of the south wall, collapsed inward due to rotation at the 

base. 

	 The MWFRS of the north half partially collapsed, with: 

	 A portion of the roof system (southeast corner) disconnected and either displaced upward 

or blown away from the supporting joist girders and walls (see Fig. 3–37 and 3–38). 

	 A section of the east wall that was braced by this portion of the roof collapsed inward due 

to rotation at the base. 

Beyond the collapsed area described above, the structural system of the north half of the 

building appeared intact. It should be noted that the fact that this portion of the building did 

not sustain more significant damage was more indicative of a less violent wind field than of 

better structural performance. 

NIST NCSTAR 3, Joplin Tornado Investigation 125 
 

 

 

 

 

 

 

 

Chapter 3 

West perimeter CMU wall 

(collapsed inward) 

Roof joists (disconnected and 

displaced upward) Joist Girder 

Figure 3–37. Roof system (decks and joists) missing at Walmart. Some roof joists 

displaced upward (top chords used to be at same elevation as top chords of joist girders, 

but now sitting above joist girders), showing evidence of wind uplift action as primary 

cause of failure. 

Missing roof system; collapsed east 

perimeter wall; joist girder bent 

upward due to uplift pressure 

Figure 3–38. Large area of roof system shown missing at Walmart. Joist girders bent 

upward due to uplift pressure. 

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Chapter 3 

	 The gravity system (steel plane frames) was mostly intact, albeit damaged, with: 

	 Most joist girders having remained in place and connected to the columns, although many 

were damaged and bent upward (again, evidence of wind uplift action prior to the failure 

of the roof system; see Fig. 3–38). There were a few girders that were disconnected from 

the columns on one end. These appeared to have been secondary failures (after loss of 

the roof system and therefore any lateral bracing for the girders). 

	 The majority of the interior columns having remained in place and connected to the 

concrete foundation. The few that were bent also appeared to have been the result of 

secondary failure. 

	 Envelope: 

	 The entryway door panels (tempered glass and aluminum frame) on the west wall were 

lost and there was damage to the fire–escape door on the east wall and to the store’s 

exterior signage. These impacts were likely due primarily to wind pressure. Whole door 

panels, including the glass and aluminum frame, were missing. (The glass on door panels 

that remained appeared intact (see Fig. 3–39). This allowed wind to infiltrate the 

building interior and resulted in increased wind uplift pressure on the roof system. 

	 Most of the membrane and rigid insulation was lost from the roof, even in the north half 

of the building where structural failure did not occur. 

	 Fatalities and Injuries: The structural collapse of the Walmart building on May 22, 2011, 

caused three fatalities and an unknown number of injuries among the approximately 200 

occupants. 

Missing door at main 

entrance 

Figure 3–39. Missing door and glass panels and damage to signage
 

at south entrance of Walmart on west wall (envelope failure allowing air
 

infiltration to the interior and causing increased wind uplift).
 

NIST NCSTAR 3, Joplin Tornado Investigation 127 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

Possible Failure Sequence: 

The observed damage and structural failures described above were assessed along with an eyewitness 

account given by a survivor who was a Walmart employee and took shelter in a designated safe area 

inside the building pursuant to Walmart’s emergency sheltering procedure. This information suggested 

that the following sequence of events likely led to the total collapse of the south half and partial collapse 

of the north half of the Walmart building: 

1.	 Wind pressure built up and caused the failure of components of the building envelope and 

wind infiltration into the building interior (through the entryway door and window panels in 

the front (west) wall, the fire–escape door in the back (east) wall, and exterior signage; see 

Fig. 3–39). 

The following was excerpted from the eyewitness account: 

“There was a very strong vacuum, and it blew out all the glass windows. 

It exploded the back. The two doors that were there in that area went 

straight open. The fire escape door that was right through them just flew 

back and just boom, boom, boom—just smacked back at an incredible 

force” (NIST Interview 99). 

2.	 Increased internal uplift pressure due to wind infiltration, combined with external uplift 

pressure on the roof, caused the roof–joist–to–joist girder connections, which tied the roof 

system to the gravity plane frame system, to fail (as evidenced by the loss of large sections of 

the roof system). Between the two critical connections of the roof system—the deck–to–joist 

connection and the joist–to–joist girder connection—the joist–to–girder connection was the 

weaker connection based on the available design information, and the net uplift pressure 

required for this connection to fail is estimated to be approximately 114 lb/ft2 (see Appendix 

H). It should be noted that the uplift pressure required for this connection to fail well exceeds 

the maximum design uplift pressure of 28.6 lb/ft2 estimated for this building based on normal 

wind design parameters in accordance with IBC 2000 (also see Appendix H). Additional 

excerpts from the eyewitness account follow: 

“And at that point, the ceiling tiles lifted up, the lights went out, and.... 

The girders99 broke all around us; they were like crashing down.”

3.	 Loss of the roof system resulted in the loss of critical lateral bracing for the exterior walls. 

The now laterally unsupported walls, which were designed with vertical beam–columns 

simply supported at the footing and at the connection to the roof system, became cantilevered 

and subsequently failed inward by overturning due to inward lateral wind pressure (see Fig. 

3–40 and 3–41). Following is another excerpt from the eyewitness: 

99 Term probably used imprecisely by interviewee. Could refer to either roof joists or joist girders. 

128 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

“So basically what happened is the ceiling fell down, landed on those 

cabinets, and then the back wall fell down on top of that, and so it 

made—the back wall made that girder squash down, so it made the front 

of our little hole be a triangle shape at about a 45–degree angle”.

East perimeter CMU wall 

(collapsed inward) 

Figure 3–40. Collapsed east wall of Walmart due to loss of roof lateral bracing and 

inward wind pressure. 

3.2.1.3 Home Depot 

Figure 3–42 shows an overview of the completely collapsed Home Depot building, located at 3110 East 

20th Street in Joplin, approximately 400 ft south of the estimated center line of the tornado damage path. 

This building was a one–story, low–rise BTS building (28 ft mean roof height and 4 ft parapet) with a 

long–span roof and RC tilt–up perimeter wall panels. The building was rectangular in plan, with 

approximate plan dimensions of 470 ft (N–S) by 250 ft (E–W). The long side of the building was in the 

north–south direction, perpendicular to the tornado direction. Figure 3–43 shows the time–history of 

wind speed near the southest corner of the building, indicating that it was subjected to an estimated 

maximum wind speed of about 170 mph ± 45 mph (EF–4 range) from a west–southwesterly direction. 

The sections below summarize the design, damage, and performance information related to the Joplin 

Home Depot. 

Design Information: 

 Year Built: 2000. 

 Building Code: BOCA National Building Code/1996. 

NIST NCSTAR 3, Joplin Tornado Investigation 129 
 

 

 

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Figure 3–41. Typical loading and design conditions for BTS building and possible failure mode. 

130 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

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© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 3–42. Aerial views of Home Depot in relation to the tornado damage path (red line denotes center of damage path).
 

Note the loss of all roof decks due to wind uplift.
 

NIST NCSTAR 3, Joplin Tornado Investigation 131 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Figure 3–43. Estimated time–history of wind speed and 

direction near the southeast corner of Home Depot. 

	 Design Parameters: Basic wind speed, 90 mph (3 second gusts),100 exposure category C. 

	 Structural System: The structural system comprised three structural components : the roof 

system, a series of five interior gravity steel frames, and the perimeter tilt–up concrete wall 

panels. The roof system and perimeter tilt–up walls formed the primary lateral load 

resistance system (MWFRS), while the interior gravity frames and the walls provided the 

primary gravity load resistance system. The descriptions of these structural components 

follow: 

	 Roof System: The structural functions of the roof were to (a) support and transfer 

vertical roof loads to the plane frames and the exterior tilt–up RC walls, and (b) provide 

lateral support for the walls. This system, which was divided into two sections by an 

expansion joint located 188 ft from the south wall (close to mid–span), included the 

following components: 

 Steel roof deck: 11⁄2 in.  36 in., 22–gauge (0.0295 in. thick) type B painted wide–rib 

steel roof deck panels supported by steel roof trusses. 

100 Design drawings indicated that the design code was BOCA NBC/1996, which specified a basic wind speed of 70 mph (fastest 

mile, or about 85 mph in 3 second gusts) for the location of the Joplin Home Depot, but also provided a specific design wind 

speed of 90 mph (5 mph higher than the code-specified basic wind speed for the building). 

132 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

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 Steel roof trusses: Primarily K series and some LH series open–web steel roof joists 

(in E–W direction), designed as simply supported, with top and bottom chords of 

adjacent joists braced against lateral buckling and uplift forces with steel bridging 

members per the Steel Joist Institute (SJI) specifications. The roof decks were 36 in. 

wide and three–span continuous, and were fastened to the roof joists (support 

fasteners) using 5/8 in. diameter puddle welds in a 36/4 fastener pattern, and along 

the side seam (side laps) using #10 Buildex screws (7 screws per span) (see Fig. 3–

44). 

	 Interior Gravity Frames: The gravity load system consisted of five plane frames (N–S) 

with typical spacing of 40 ft. Each had 10 columns (11 spans). This system transferred 

vertical loads from the roof to the foundation through connections with the roof joists. 

Each span consisted of an open–web steel joist girder supported on each end by structural 

steel square tube columns (TS 8  8  0.25) through a simple shear connection using 

either two 3⁄4 in. diameter A325 bolts or two 1⁄4 in.  2 in. fillet welds (E70 electrode). 

The bottom chord of the joist girder straddled but was not connected to the column’s 

stabilizer plate (see Fig. 3–45). Each column was supported on a 14 in.  14 in.  3⁄4 in. 

steel base plate that was anchored into the concrete individual footing using four 3⁄4 in. 

diameter hooked anchors. 

© 2013 Homer TLC, Inc. Used with 

permission. 

© 2013 Homer TLC, Inc. Used with permission. 

Figure 3–44. Typical connection between 

the roof system and the perimeter 

tilt–up RC wall at Home Depot. Figure 3–45. Typical connection 

between roof joist girder and interior 

column at Home Depot. 

NIST NCSTAR 3, Joplin Tornado Investigation 133 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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	 Perimeter Walls: The walls supported both gravity and lateral loads and acted as shear 

walls laterally braced for stability by the roof system acting as a horizontal diaphragm. 

They were typically designed following the American Concrete Institute (ACI) 

Committee 551 guidance on tilt–up concrete structures. The walls consisted of 73 tilt–up 

RC non–composite sandwich panels, each 12 in. thick and comprising three layers: a 71⁄2 

in. thick RC structural wythe, a 11⁄2 in. thick layer of insulation, and a 3 in. thick concrete 

fascia wythe (exterior shell). Panel heights varied from 26 ft 8 in. to 34 ft, and their 

widths varied from 13 ft to 25 ft 73⁄4 in. The connections for the Joplin Home Depot tilt–

up panels were as follows: 

 Panel–to–footing connection: The bottoms of the tilt–up panels extended a short 

distance below the concrete floor slab/soil surface level and were supported on strip 

RC footings. For the majority of the tilt–up wall panels (64 of 73), the panel–to–

footing connections were primarily by friction101 (i.e., there was no positive 

anchorage between the bottom of the wall and the footing), with the only connection 

afforded by embedment of #4 reinforcing bars at 24 in. spacing between the sides of 

the walls and the concrete slab–on–grade (mainly to restrain against lateral 

movement; see Fig. 3–47). This combination of friction–only connection to the 

footing and dowel embedment to the slab–on–grade provided restraint to lateral 

movement but not against rotation at the base of the wall panels. However, for the 

remaining nine tilt–up panels, which were all located at the northeast corner of the 

building around the loading dock, the wall–to–footing connections were more robust 

with mechanical connections to the strip footing (through the use of dowels 

connected to an 18 in.  18 in. concrete block on top of the footing) in addition to the 

dowel connections to the floor slab (see Fig. 3–46). This positive connection to the 

strip footing, likely designed to protect against the potential for delivery trucks 

accidentally striking walls in the loading dock area, provided these 9 panels with a 

partially fixed base connection and thus a more robust rotational restraint compared 

with the other 64 panels with friction–only connections (see Fig. 3–47). 

 Panel–to–roof–joist connection: The tilt–up wall panels were braced laterally by the 

roof system through connections with the roof trusses. Each roof truss was 

connected at the top chord to steel seat angles embedded to the tilt–up panel by two 

1/8 in.  1 in. field fillet welds (E70XX) and one 3/16 in.  1 in. field fillet E70XX 

weld (see Fig. 3–48). 

 Panel–to–panel connection: Adjacent panels were not connected along their vertical 

sides. 

	 Components and Cladding: 

	 Envelope: The building envelope consisted of concrete exterior walls and rolling steel 

doors. 

101 This is not inconsistent with design guidance by industry standard (ACI 551) for areas with low or no seismic risk. 

134 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

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Figure 3–46. Positive wall–to–footing 

connection (dowels connection to 

footing and concrete block, in 9 tilt–up 

wall panels near loading dock) at 

Home Depot. 

Figure 3–47. Friction–only wall–to–

footing connection (in remaining 64 

tilt–up RC wall panels) at Home Depot. 

© 2013 Homer TLC, Inc. Used with permission. © 2013 Homer TLC, Inc. Used with permission. 

Figure 3–48. Roof framing plan (right) and typical roof joist–to–wall panel welded connection (left). 

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	 Roof Covering: On the steel roof deck, there were rigid insulation panels covered by 

single–ply EPDM roofing membrane. 

Damage and Performance Information: 

	 The MWFRS (perimeter tilt–up walls and roof system) completely collapsed: 

	 The entire roof system (roof deck and roof joists) disconnected from the perimeter wall 

panels and the gravity plane frames, with almost all of the roof joists disconnected, 

displaced upward, or completely blown away from the supporting joist girders and walls 

(for evidence of wind uplift action, see Fig. 3–42 and 3–49). Note that where the roof 

system did not get blown away from the site, some of the metal roof decks appeared to 

remain connected to the roof joists (through the field puddle–weld connections). 

	 Sixty–three out of 73 tilt–up panels collapsed either inward or outward and only 10 

remained standing. Of the 63 collapsed panels, all but 2 had the friction–only connection 

to the strip footing (see Fig. 3–46, 3–47, and 3–48). The 10 uncollapsed panels were 

adjacent to each other and were part of the group of panels located around the loading 

dock at the northeast corner of the building. Seven of these 10 had positive connections 

to the footing. The three with friction–only connections to the footing that also remained 

standing appeared to have been supported against outward rotation by steel shelving 

located on the exterior side of these panels (see Fig. 3–50). 

	 All five of the steel plane frames (gravity load system) were damaged but remained generally 

at their original locations (were not blown away): 

	 Many joist girders bent laterally or disconnected on one end from the interior columns. 

These appeared to have been secondary failures after the loss of the roof system and 

therefore the loss of any lateral bracing for the girders and the frames. 

	 Many interior columns either buckled at mid–height or disconnected at the base (fracture 

or pull–out of anchors) from the slab–on–grade. These failures also appeared to be 

secondary failures that occurred after the loss of lateral bracing due to failure 

(disconnection) of the roof deck (see Fig. 3–51). 

	 The loss of the entire roof system and collapse of the wall panels represented a failure of the 

building envelope. It is not known if the doors on the north, east, or west walls were 

breached prior to the collapse of the entire building. However, the rolling steel doors at the 

loading dock on the north wall (uncollapsed wall panels) appeared to have remained closed 

during and after the tornado. 

	 Fatalities and Injuries: Death certificates obtained by NIST showed that eight fatalities 

occurred at the Home Depot. The deaths were likely the result of the structural collapse of 

the building. However, NIST has not been able to definitively confirm the exact locations of 

the victims inside the Home Depot or the circumstances related to their deaths. 

136 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

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Tilt-up wall panels in northeast corner 

(remained standing) 

Figure 3–49. Collapsed Home Depot building (view from the northwest). Note the loss of 

all roof decks and upward displacement of joists and joist–girders. 

North tilt-up wall 

East tilt-up wall panels 

panels 

Loading dock 

Steel 

shelves 

Figure 3–50. Ten tilt–up panels in the northeast corner of the Home Depot remained 

standing. Seven of these 10 panels had positive connections to the footing and thus 

some degree of restraint against rotation. The other three uncollapsed panels had 

friction–only connections to the footing but appeared to have been supported against 

falling outward by steel shelving on the exterior side (Garden Center). 

NIST NCSTAR 3, Joplin Tornado Investigation 137 
 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

Missing roof deck and roof 

joists. Only joist girders 

remained but heavily damaged. 

Figure 3–51. Damaged joist girders and interior columns at Home Depot. Note the 

complete loss of the roof system that was connected to the girders. 

Possible Failure Sequence: 

The observed damage and structural failures described above suggested that the following sequence of 

events ultimately led to the total collapse of the Joplin Home Depot building: 

1.	 Wind uplift pressure caused the failure of the roof joist–to–joist girder connections, which 

tied the roof system to the gravity plane frames and the perimeter tilt–up walls; this resulted 

in the loss of required lateral bracing for both the plane frames and the walls (as evidenced by 

the absence of almost the entire roof system). Available design information indicated that, 

between the two critical connections of the roof system (deck–to–joist and joist–to–joist 

girder), the joist–to–joist girder was the weaker one and the one likely to have failed first 

(again evidenced by the loss of the entire roof system) (see Appendix I). Note that the 

estimated uplift pressure required to incur this failure well exceeds the maximum design 

uplift pressure of 26.2 lb/ft2 estimated for this building based on normal wind design 

parameters in accordance with BOCA NBC/1996. 

2.	 Failure of the roof system resulted in the loss of critical lateral bracing for the exterior tilt–up 

wall panels as well as for the steel plane frames. The now laterally unsupported tilt–up wall 

panels that relied on friction–only connections to the footing loads (except for the three 

panels that were supported by steel shelving in the Garden Center) became unstable and 

collapsed due to lateral pressures, and those wall panels around the loading dock in the 

northeast corner of the building that had partially fixed end connections through positive 

connections to the footing were able to resist the overturning moment and remained standing. 

138 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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3.2.1.4 Joplin East Middle School 

The Joplin East Middle School was a building complex comprising several joined sections. The complex, 

located at 4594 East 20th Street in Joplin (toward the end of the tornado damage path ), had a long and 

narrow configuration and was oriented in the north–south direction (total length of 664 ft) as shown in 

Fig. 3-52. It was designed in 2007 and constructed in 2009. All sections (denoted as Sections C, D, E, 

and F on Fig. 3–53) of the building complex were made primarily of reinforced CMU walls with short–

span steel roof decks, except for the Auditorium building (denoted as Sec. B on Fig. 3–53), which had a 

longer roof span, and the Gymnasium building (denoted as Sec. A), which had precast tilt–up perimeter 

walls in addition to a longer roof span. 

Of the entire school complex, the south end, where the Gymnasium and Auditorium were located, was 

closest to the estimated center line of the tornado damage path (see Fig. 3–52), and was affected by an 

estimated maximum wind speed of 170 mph ± 45 mph (EF–4 range) from a northwesterly direction (see 

Fig. 3–54). Along the length of the complex, there was a sharp gradient in wind speed with the north end 

affected by much lower wind speeds compared to those that affected the south end. Consequently, and 

due to the fact that most building sections of the north end of the school had shorter span roofs, these 

sections (north of the Gymnasium and Auditorium) sustained only minor damage to their building 

envelopes, while the Auditorium and Gymnasium buildings sustained total structural collapse of their 

roof systems and partial collapse of their perimeter walls. Below is design, damage, and performance 

information pertaining to the two collapsed sections of Joplin East Middle School, the Gymnasium and 

Auditorium buildings. 

Gymnasium Building—

The school gymnasium was a one–story BTS building with a long–span roof (102 ft) and precast concrete 

tilt–up wall panels that were laterally braced by steel roof decks to form the lateral load resistance system. 

The roof decks were supported by single–span, open–joist, curved (bow–string) steel roof trusses. The 

building was approximately 102 ft (N–S) by 142.2 ft (E–W) in plan dimension, and had a mean roof 

height of 39.8 ft (the east and west walls were curved with minimum heights of 35.3 ft and maximum 

heights of 43.3 ft). The floor was a 4 in. RC slab–on–grade with 6  6, W1.4  W1.4 WWF 

reinforcement. 

Design Information: 

	 Year Built: 2009. 

	 Building Code: 2000 IBC. 

	 Design Parameters: Basic wind speed, 90 mph (3 second gusts); Importance Factor I = 1.0; 

exposure category C. 

	 MWFRS: The MWFRS comprised two subsystems: the roof; and the perimeter tilt–up 

precast concrete wall panels. 

NIST NCSTAR 3, Joplin Tornado Investigation 139 
 

 

 

 

 

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© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 3–52. Aerial views of Joplin East Middle School in relation to the tornado damage path (red line denotes 

center of damage path). 

140 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

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Figure 3–53. Layout of the Joplin East Middle School building complex.
 

The Gymnasium (A) and Auditorium (B) sustained the greatest damage in the tornado.
 

NIST NCSTAR 3, Joplin Tornado Investigation 141 
 

 

 

 

 

 

 

 

 

 

 

 

 

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Figure 3–54. Estimated time–history of wind speed and direction near 

the south end of Joplin East Middle School (over the Gymnasium). 

	 Roof System: This structural subsystem provided lateral bracing for the perimeter
 

precast wall panels, and consisted of the following:
 

 Steel roof decks: 3 in. deep  24 in. wide, 20–gauge (thickness: 0.358 in.), three–

span, type NA acoustic roof decks (this type of roof deck is well–suited for 

applications where it is desirable to space the supporting members as far apart as 

possible as in the case of school gymnasiums). The roof decks were fastened to the 

supporting steel trusses by 5/8 in. diameter puddle welds using a 24/4 connection 

pattern. Adjacent deck panels were connected along the side lap using #10 Buildex 

screws with 10 screws per span. 

 Steel roof trusses: 14 single, long–span (102 ft span) bow–string trusses, installed in 

the N–S direction (supported on top of north and south walls) and with 10 ft 

spacings. The first and last trusses were 5 ft from the end walls (east and west walls). 

Adjacent trusses were laterally braced with L 21⁄2  21⁄2  3/16 steel angles. The first 

two trusses from each end wall were additionally braced together at the top and 

bottom chord using L 31⁄2  31⁄2  1⁄4 steel angles. The first and last trusses were 

braced to the walls with horizontal bridging at top and bottom chords using 11 L 21⁄2 

 21⁄2  3/16 angles. Each end of a truss was welded to a 3/8 in. bent plate, which 

was then welded onto an L 8  8  1⁄2, 1 ft 9 in. long steel seat angle embedded on the 

top and at the center of the precast tilt–up wall panel with four vertical, 1⁄2 in. 

diameter, 10 in. long headed studs and three horizontal, 1⁄2 in. diameter, 6 in. long 

headed studs. 

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	 Perimeter Walls: The walls supported both gravity and lateral loads and acted as shear 

walls laterally braced by the roof horizontal diaphragm system. They were typically 

designed following the ACI 551 guidance on tilt–up concrete and the Precast/Prestressed 

Concrete Institute’s (PCI) PCI Design Handbook: Precast and Prestressed Concrete 

(PCI 1999). They consisted of 50 precast concrete tilt–up panels with widths of 10 ft and 

6 ft ((46) 10 ft wide panels and (4) 6 ft wide panels). Each panel had three layers: a 10 

in. thick inner layer of precast structural concrete; a middle layer of thermal insulation; 

and an outer layer of brick façade. Each panel was connected to the cast–in–place (CIP) 

concrete footing at two points along the bottom of the wall panel using 1/4 in. fillet welds 

(the welds connected two steel plates embedded on the interior face of each wall panel 

(PL 6 in.  8 in.  3/8 in.) to two steel plates (PL 4 in.  6 in.  3/8 in.) embedded in the 

CIP footing). This connection provided restraint against lateral translation of the wall 

panel but very little restraint against wall rotation (hinge). Adjacent wall panels were 

linked at the top by a cap beam made of steel channel, which extended from the end of 

one roof truss to the adjacent roof truss (from the middle of one wall panel to the next), 

and were also connected at two points along their vertical seams by welding a 4 in.  8 in. 

 3/8 in. steel plate to steel plates embedded in the precast walls. 

	 Components and Cladding: 

	 Envelope: Exterior brick façade. 

	 Roof covering: The covering comprised a standing seam metal–barrel roof system over 

single–ply roof membrane over 4 in. insulation over 5/8 in. type X gypsum board 

(thermal barrier) over a steel roof deck. 

	 Other Features: Unlike other stand–alone BTS buildings (e.g., Walmart, Home Depot), 

which typically have the roof deck act as the sole lateral bracing system for all perimeter 

walls, the Joplin East Middle School Gymnasium building was part of a building complex 

and was surrounded by other building sections. As such, three of the four perimeter walls of 

the Gymnasium (the north, south, and east walls) were laterally braced on their opposite sides 

through connections with the roof systems of the surrounding building sections, as well as 

laterally braced by the Gymnasium’s roof system (see Fig. 3–55). Thus, the only wall of the 

Gymnasium that was actually braced solely by its own roof was the west wall. The tilt–up 

panels of this wall were the ones that collapsed as a result of the May 22, 2011, Joplin 

tornado, as is discussed below. 

Damage and Performance Information: 

The damage observed at the Joplin East Middle School Gymnasium building included: 

1.	 The loss of all roof covering materials and most of the metal roof decks (see Fig. 3–56 and 3–

57). The disconnection of the roof decks from the supporting bow–string roof trusses 

appeared to be due to failure of the puddle welds (whole panels, each three–span or 30 ft 

NIST NCSTAR 3, Joplin Tornado Investigation 143 
 

 

 

 

 

 

 

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© 2007 Patterson Latimer Jones Brannon Denham (P.L.J.B.D.). Used with permission. Enhancements by NIST. 

Figure 3–55. Lateral bracing for Joplin East Middle School Gymnasium walls. 

Collapsed tilt-up panels of 

west wall 

Metal roof decks missing Collapsed bow-string 

roof trusses 

Figure 3–56. Joplin East Middle School Gymnasium building, viewed from
 

the west, showing complete loss of steel roof deck, disconnection and
 

collapse of the first two bow–string steel trusses, and collapse of 9 out
 

of 11 tilt–up panels of the west wall.
 

144 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

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Roof deck displaced upward and 

torn from roof truss (failure of 

puddle welds due to uplift 

pressure) 

Figure 3–57. Disconnection of steel roof deck of Joplin East Middle School Gymnasium 

due to failure of puddle welds due to uplift pressure. 

long, were disconnected at puddle–weld locations). A few perimeter wall panels fell into the 

interior of the building, while most were blown away from the building. The loss of the roof 

decks effectively removed the interior lateral bracing for the tilt–up wall panels of the north, 

south, and east walls (these walls, however, were still braced on the exterior by the roof 

systems of the surrounding building sections as described above) and the sole lateral bracing 

system for the tilt–up panels of the west wall. 

2.	 The disconnection and collapse of the first two bow–string roof trusses (nearest to the west 

wall). Both of the collapsed trusses sustained lateral, out–of–plane bending, and their 

disconnections from the top of the tilt–up wall panels appeared to have resulted from shear 

failure at the embedded seat angles at the ends of each truss (either shear fracture of the welds 

between the vertical headed studs that were embedded in the concrete or of the welds 

connecting the joist to the seat angle; see Fig. 3–58 and 3–59). 

3.	 The collapse of 9 out of 11 tilt–up wall panels of the west wall toward the building’s interior

(along the tornado’s translational direction). These collapsed panels became truly unbraced 

laterally after the disconnection and loss of the roof decks. The two panels of this wall that 

did not collapse were end panels that were also laterally supported along their height by 

bearing against the end panels of the north and south walls. Thus, these two panels did have 

some lateral support aside from the lateral bracing provided by the roof system, unlike the 

nine intermediate panels that collapsed. 

NIST NCSTAR 3, Joplin Tornado Investigation 145 
 

 

 

 

 

 

 

 

 

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Metal roof deck missing 

Collapsed bowstring roof trusses 

Collapsed west wall 

Figure 3–58. Collapsed bow–string roof trusses and collapsed west
 

wall tilt–up panels in the interior of the Joplin East Middle School Gymnasium.
 

Figure 3–59. Seat angle welded to end of bow–string roof truss and
 

embedded into top of tilt–up panel got disconnected. Note missing
 

vertical headed studs (4, each 10 in. long), which appeared to have been
 

sheared off from the angle. The three horizontal studs remained connected
 

to the seat angle but pulled out from the concrete.
 

146 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Possible Failure Sequence: 

Calculations using the design information obtained for this building indicated that the roof deck–to–joist 

connection (by 5/8 in. diameter puddle welds) was the weakest link in the overall uplift resistance of the 

building (weaker than the joist–to–wall connection). However, the uplift capacity of the roof deck–to–

joist connection was well above the required maximum design uplift pressure of 17.3 lb/ft2 based on the 

90 mph basic design wind speed (thus, this building would not have failed the way it did under a code–

level wind event; see Appendix J). The fact that the roof deck–to–joist connection was the weakest link 

for uplift resistance suggested that the steel roof decks were the first elements to fail, and this failure 

occurred due to tension failure of the puddle welds. This is consistent with the observed roof deck failure 

shown in Fig. 3–56 and 3–57. This is also corroborated by videos of the interior of the building recorded 

by security cameras during the storm, which showed roofing materials, including some roof deck panels, 

falling into the interior of the building prior to the collapse of the west wall panels.102 

The failure of the roof deck–to–joist connection and subsequent loss of all the roof decks resulted in nine 

tilt–up panels of the west wall becoming laterally unsupported and simply overturning at the base in the 

direction of lateral wind load (west to east). As these panels fell toward the interior of the building, they 

impacted the first two bow–string roof trusses that were nearest to them (and within their collapse radius), 

resulting in out–of–plane bending of the trusses, subsequent shear failure of the truss–to–wall 

connections, and ultimately the collapse of these two roof trusses (see Fig. 3–58, 3–59, and 3–60). 

In sum, the sequence of failure of the Joplin East Middle School Gymnasium building was as follows: 

1.	 The roof deck–to–joist connections failed due to tension (uplift) failure of the puddle–weld 

connections. 

2.	 Nine tilt–up panels (out of 11) of the west wall became unsupported laterally and collapsed 

due to overturning moment at the base of the wall panels. 

3.	 As these nine panels overturned, they impacted the first two roof joists that were within the 

walls’ collapse radius, causing them to fail also (secondary failures). 

The tornado occurred on a Sunday and the Gymnasium was unoccupied at the time of the collapse. Thus, 

there were no fatalities or injuries associated with the collapse of this building. 

Auditorium Building—

The Auditorium was housed in a one–story BTS building with reinforced CMU exterior walls. The 

approximate plan dimension was 92.6 ft (N–S) by 113.8 ft (E–W), and the mean roof height was 31.6 ft. 

The floor was a 4 in. RC slab–on–grade with 6  6, W1.4  W1.4 WWF reinforcement. 

Design Information: 

	 MWFRS: The MWFRS comprised two structural subsystems: the roof system that provided 

lateral bracing for the perimeter reinforced CMU walls, and the perimeter reinforced CMU 

walls. 

102 The “Gym NE,” “Gym SE,” “Gym NW,” and “Gym SW” videos were made available by Joplin Schools. 

NIST NCSTAR 3, Joplin Tornado Investigation 147 
 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

Collapsed 

west wall 

Collapsed bow-string trusses 

© 2007 Patterson Latimer Jones Brannon Denham (P.L.J.B.D.). Used with permission. Enhancements by NIST. 

Figure 3–60. Elevation showing first two bow–string roof trusses and 

collapse radius of west wall at Joplin East Middle School Gymnasium. 

	 Roof System: This structural subsystem consisted of the following components: 

 Steel roof decks: 11⁄2 in. deep by 36 in. wide, 22–gauge, wide–rib painted (type B) 

and galvanized acoustic (type BA), three–span continuous steel decks. The decks 

were fastened to the supporting steel trusses (frame fastener) by 5/8 in. diameter 

puddle welds using a 36/4 connection pattern. Adjacent deck panels were connected 

along the side lap (side lap fastener) using #10 Buildex screws with two screws per 

span. 

 Steel roof trusses: The roof trusses consisted of K series open–web steel roof joists, 

running in the E–W direction at 5 ft spacing, supported by steel joist girders in the N–

S direction. Each joist end was welded to a 5 in.  1/4 in.  9 in. steel plate with two 

3/8 in. diameter  4 in. long headed studs that were anchored into the bond beam in 

the CMU wall. 

	 Perimeter Walls: These were reinforced CMU walls with 12 in. concrete blocks, stacked 

bond with horizontal reinforcing at 16 in. on center and with cells filled with grout. Each 

CMU wall had an overall thickness of 1 ft 91⁄2 in., and included three layers: a single–

wythe 12 in. concrete masonry block over 2 in. of rigid insulation over air space over 

masonry veneer. The walls were connected to the concrete foundation using 4.5 ft long 

number 6 dowels, placed at mid–depth of the CMU wall at every 2 ft interval, with a 2.5 

ft embedment into the wall (3.5 units of CMU). The walls were grouted and reinforced in 

the vertical direction (at every two masonry units) as well as in the longitudinal direction, 

including longitudinal reinforcement for the cap beam at the top of the walls. In the 

interior of the building were two concrete masonry walls that divided the Auditorium into 

two sections, a stage and an audience section. 

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	 Components and Cladding: 

	 Envelope: Exterior masonry veneer. 

	 Roof Covering: Single–ply roof membrane over 1/2 in. protection board over 4 in. 

insulation over steel roof deck. 

	 Other Features: Similar to the Gymnasium, the Auditorium was surrounded by other sections 

of the school complex on the north and west sides. Because of that, in addition to being 

braced laterally by their own roof system, the north and west perimeter walls were also 

braced on their opposite sides through connections with the roof systems of the adjacent 

building sections. Thus, of the four perimeter walls, only the east and south walls were truly 

dependent upon the roof diaphragm as the sole lateral bracing system. These east and south 

perimeter walls were the ones that collapsed as a result of the tornado, as is discussed below. 

Damage and Performance Information: 

The Auditorium building sustained total collapse, with damage that included: 

1.	 The disconnection and loss of roof decks in part of the roof, and the collapse of the entire roof 

system (trusses, steel deck, and roof covering) into the building interior (see Fig. 3–61 and 3–

62). 

2.	 Collapses of the east and south perimeter CMU walls, with the south wall collapsed into the 

building (toward the north) and the east wall collapsed outward, away from the building 

(toward the east). Similar to the collapsed CMU walls of other BTS buildings in the May 22, 

2011, Joplin tornado, the east and south walls failed due to overturning of the entire wall at 

the wall–to–foundation connections, rather than due to inadequate strength within the CMU 

walls (see Fig. 3–63). 

Possible Failure Sequence: 

Calculations using design information obtained for the Auditorium building indicated that the roof deck–

to–joist connection (by 5/8 in. diameter puddle welds in a 36/4 pattern) was the weakest link in the overall 

uplift resistance of the building. However, the uplift capacity of the roof deck–to–joist connection was 

well above the required maximum design uplift pressure of 17.3 lb/ft2 based on the 90 mph basic design 

wind speed (thus, the roof diaphragm would not have failed under a code–level wind event). The fact that 

the roof deck–to–joist connection was the weakest link for uplift resistance suggested that the steel roof 

decks were the first elements to fail, and that their failure was due to tension failure of the puddle welds. 

The failure of the roof deck–to–joist connections and subsequent loss of roof diaphragm action resulted in 

the south and east walls becoming laterally unsupported, and they subsequently collapsed due to 

overturning at the base in the direction of lateral wind load. 

In sum, the sequence of failure of the Auditorium building was as follows: 

1.	 The roof deck–to–joist connections failed due to tension (uplift) failure of the puddle–weld 

connections. 

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2.	 The failure of the roof system caused the perimeter CMU walls to lose lateral support on the 

interior side of the building. While the north and west walls remained braced laterally 

through connections with the roof systems of adjacent sections, the south and east walls lost 

their sole lateral support and subsequently collapsed due to overturning. 

Figure 3–61. View from east of Joplin East Middle School Auditorium building. 

Figure 3–62. In the wreckage of the Joplin East Middle School Auditorium, missing roof 

deck from top of joist—only puddle–weld marks remained. 

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Figure 3–63. Collapse due to overturning (outward) of east perimeter Joplin East Middle 

School Auditorium wall after loss of roof diaphragm. 

3.2.1.5 Joplin High School 

Joplin High School was a building complex that, similar to Joplin East Middle School, comprised several 

individual but connected buildings of different ages and structural systems. The school, at 2104 Indiana 

Avenue in Joplin, was oriented in the north–south direction, with the southeast portion in close proximity 

to the estimated center of the tornado damage path (see Fig. 3–64). This portion of the school complex 

was subjected to an estimated maximum wind speed of 170 mph ± 45 mph (EF–4 range, from westerly 

direction, see Fig. 3–65), and it was the buildings of this portion of the school complex that sustained 

structural damage and collapsed. 

The buildings at Joplin High School had two main structural systems, both typical of building systems in 

the region: (1) RC frame (two buildings); and (2) BTS with CMU perimeter walls braced by steel roof 

diaphragms supported by open–web steel roof joists and joist girders. NIST was able to obtain only 

partial sets of drawings for this facility. The available drawings included those of building sections that 

were added over time to the school complex (PE Addition building, added in 1989; Multimedia Learning 

Center in 1997; and TV Studio in 2004). The two RC frame buildings, located at the north end of the 

school complex, were likely the original school buildings (constructed in the late 1960s). All other 

sections of the school complex, including the newly added sections identified above, were BTS buildings 

with CMU walls and steel roof diaphragms as indicated above. 

The damage observed at Joplin High School closely followed the pattern of damage observed for 

buildings of similar construction in the affected area. In other words, the damage to the two RC frame 

buildings at the north end of Joplin High School followed the same pattern as that observed for the RC . 

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© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 3–64. Overview of Joplin High School complex, with estimated center line of Joplin tornado damage 

path shown in red. 

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Figure 3–65. Estimated time–history of wind speed and 

direction near the southeast corner (closest to center of 

tornado damage path) of Joplin High School. 

frame building of SJRMC (the West Tower), and the damage to the other, BTS sections of the school 

followed a pattern similar to that observed for other BTS buildings such as the Walmart. The main 

damage to the buildings of Joplin High School is described below: 

	 The two RC frame buildings and other building sections making up the north end of the 

school complex sustained damage primarily to their vertical building envelopes. These 

buildings were similar in design, each a three–story structure with one story below ground. 

Each building’s structural system consisted of an RC frame made of circular columns and 

rectangular beams, supporting RC floors and composite, concrete–steel roof decks. Between 

the column lines there were interior, non–load–bearing unreinforced masonry (URM) 

partition walls. The exterior, vertical envelope consisted of a combination of brick and 

aluminum stud walls supporting cement–based boards and glass windows. While these 

buildings sustained no damage to their structural systems, the damage to their envelopes, 

which included the breakage and collapse of portions of the brick curtain walls and most of 

the aluminum stud curtain walls, resulted in a complete loss of function in both buildings due 

to subsequent damage to their interiors (electrical, HVAC systems, etc.). The roof envelopes, 

made of composite concrete–steel decking, appeared undamaged. Figure 3–66, 3–67, and 3–

68 show views from the exterior of the two RC frame buildings and from the interior of the 

school building section that linked these buildings; these photographs were taken 3 days after 

the tornado on May 25, 2011. 

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Figure 3–66. View from the exterior showing damage to the envelope 

of one of the RC frame buildings (east building) of Joplin High School. 

Figure 3–67. View from the exterior showing damage to the envelope 

of one of the RC frame buildings (west building) of Joplin High School. 

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Figure 3–68. Damage and 

debris in an interior hallway of 

Joplin High School. 

	 Several BTS buildings collapsed, including the Gymnasium and Auditorium and smaller 

buildings with CMU walls and open–joist steel roof truss/steel roof deck diaphragm systems. 

The Gymnasium and Auditorium had similar structural systems. Both were BTS buildings 

with long–span, open–joist steel roof trusses and a steel roof deck diaphragm. They were 

located on the south end of the school close to the estimated center of the tornado damage 

path. 

Following is additional information about the design and performance of the damaged BTS structures. 

Gymnasium Building—

The Gymnasium’s structural system consisted of a series of steel frames made of wide–flange columns 

supporting open–web steel joist girders. The columns were supported on a concrete floor slab through 

bolted connections and enclosed in the CMU perimeter walls. The steel frames supported long–span, 

open–web steel joist girders and roof joist systems. The building envelope consisted of 22–gauge, wide–

rib, three–span continuous steel roof decks (horizontal envelope) and two–layer exterior walls (inner layer 

made of CMU and outer layer of bricks). 

The building sustained a total collapse of both the structural frame and the envelope, including: (a) the 

disconnection and loss of all steel roof decks; (b) failures of the column–to–floor bolted connections and 

of the embedded connections between the roof girders and the tops of the CMU walls, which resulted in 

the collapse of several individual steel columns and of the entire roof system; and (c) the collapse of large 

portions of the east and west exterior walls due to loss of lateral bracing from the roof system. Figure 3–

69 shows a view of the collapsed Gymnasium building. 

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Figure 3–69. View from west of the Joplin High School Gymnasium building. 

Auditorium Building—

The structural system of the Joplin High School Auditorium consisted of six individual steel frames, each 

made of open–web deep steel joist girders connected to a wide–flange steel column at each end. Adjacent 

frames were braced by diagonal steel angles, both vertically and diagonally, and supported a series of 

smaller open–web steel roof joists. The roof joists in turn supported panels of wide–rib steel roof decks 

(22–gauge, 36 in. wide, three–span continuous panels). The details of the roof deck–to–joist and joist–to–

joist girder connections for the Auditorium were not available due to a lack of design drawings for the 

building. Besides the steel roof deck and roof covering, the building envelope consisted of exterior walls 

made of an inner layer of URM wall (non–grouted) and a brick outer layer. 

The structural steel frames of the Auditorium building appeared to have sustained only minor damage, 

with all six frames remaining intact despite the failure of a few lateral braces between them. However, 

the damage to the roof (lateral bracing) system was significant, with (a) disconnection and complete loss 

of most of the steel roof deck panels; (b) loss of a large number of the open–web steel roof joists in 

several spans; and (c) the collapse of most of the exterior URM/brick walls. Figure 3–70 shows the north 

side of the Auditorium building. 

Other Smaller BTS Buildings—

These single–story BTS buildings typically had CMU walls made of three layers (a partially grouted and 

reinforced concrete masonry inner layer, a foam insulation middle layer, and an outer brick layer). The 

top course of the CMU at the top of the wall was grouted to form a continuous cap beam for anchorage of 

the steel roof joists. The bottom of the CMU wall was anchored (only about 6 in. deep) into the concrete 

footing with steel reinforcing bars. The typical damage to these buildings included disconnection and loss 

of panels of the steel roof deck and failure of the connection between the steel roof joists and the CMU 

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walls, and ultimately, the collapse of a large portion of the exterior CMU walls due to loss of lateral roof 

bracing (see Fig. 3–71, 3–72, and 3–73) 

Figure 3–70. View from north of the Joplin High School Auditorium building. 

Figure 3–71. Failure of joist–to–CMU wall connection due to uplift at Joplin High School. 

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Figure 3–72. Collapse of CMU wall due to loss of lateral roof bracing at Joplin High
 

School.
 

Figure 3–73. Short anchorage between CMU wall and concrete footing at Joplin High
 

School.
 

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3.2.1.6 Franklin Technology Center 

The Franklin Technology Center was a trade school located at 2020 Iowa Street, about 300 ft directly 

west (across the street) from Joplin High School, and 250 ft north of the center of the tornado damage 

path. Figure 3–74 shows an overview of this building, which completely collapsed, as it existed shortly 

after the May 22, 2011, Joplin tornado. Figure 3–75 shows the estimated time–history of wind speed, 

which indicates that the building was affected by a maximum wind speed of approximately 160 mph ± 40 

mph (EF–3 to EF–4 range). 

The building was a typical short–span, one–story BTS building with lightly reinforced CMU perimeter 

walls laterally braced by single–span steel roof systems (open–web steel roof joists supporting wide–rib 

steel roof decks). The building was rectangular in plan and oriented in the north–south direction, and 

consisted of two sections of similar design: the original north half, constructed in the late 1960s, and the 

1978 south–half addition. NIST was able to obtain only a partial set of the design drawings for this 

building. Below is design, damage, and performance information for the center. 

Design Information: 

	 Year Built: Original facility (north half), late 1960s; south–half addition, 1978. 

	 Building Codes: Information not available. 

	 Design Parameters: Information not available. 

	 Structural System: The building was a one–story, low–rise BTS with a short, single–span 

flexible diaphragm steel roof. The structural system comprised two structural components 

that formed the MWFRS of the building: the roof system; and the perimeter CMU walls. 

	 Roof System: The roofing consisted of open–web steel roof joists with 6 ft typical 

spacing, supporting a built–up roof over 3 in. rigid insulation and 11⁄2 in., 22–gauge, 

wide–rib, three–span continuous steel roof decks. The roof decks were fastened to the 

supporting roof joists primarily by puddle welds. However, design information on the 

roof deck–to–joist fastening pattern was not available. The ends of the roof joists were 

welded onto embedment plates that were anchored into the bond beam at the top of the 

perimeter CMU walls with two hooked studs (see Fig. 3–76). 

	 Perimeter Walls: The partially grouted CMU exterior walls were covered by a layer of 

rigid foam insulation and an outer layer of brick veneer. The top course of the CMU 

walls was grouted and reinforced with two #4 longitudinal steel reinforcing bars to form a 

continuous horizontal bond beam for anchoring the ends of the roof joists. The CMU 

walls were also reinforced vertically with #4 reinforcing bars at every 2 ft 8 in. on center. 

The vertical reinforcements were lapped with #4 reinforcing dowels connecting the CMU 

walls to the concrete footing. 

	 Envelope: The building envelope included the roof (built–up roof over rigid insulation) and 

the walls (brick veneer over rigid foam insulation with openings (doors, windows, and 

sectional garage doors) on all four elevations. 

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© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 3–74. Overview of damage at Franklin Technology Center, with center line of tornado damage path (in red). 

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Figure 3–75. Estimated time–history of wind speed and direction 

near the southeast corner of Franklin Technology Center. 

CMU bond beam 

Steel roof truss 

Figure 3–76. Steel roof deck and roof joist connection to CMU wall bond beam at
 

Franklin Technology Center.
 

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Damage and Performance Information: 

The building sustained complete structural collapse. This collapse was typical of the structural failures 

observed for other BTS buildings that experienced similarly strong wind uplift in the May 22, 2011, 

Joplin tornado: 

	 The entire roof system (roof deck and roof joists) disconnected from the perimeter CMU 

walls. This involved both (a) the loss of the steel roof deck diaphragm (failure due to tension 

uplift of the puddle welds), and (b) disconnection of the steel roof joists (while they remained 

connected to the CMU bond beam) from the remainder of the walls along the mortar joint 

between the bond beam and the CMU course below the bond beam (the vertical load path in 

the wall was disrupted at the mortar joint between the bond beam and the CMU course below 

due to uplift pressure. NIST was not able to determine if the wall’s vertical reinforcements 

were anchored into the bond beam). Thus the bond beam, while remaining continuous 

horizontally and connected to the roof joists, was separated from the remainder of the 

perimeter walls due to wind uplift action (see Fig. 3–77). 

CMU bond beam 

Figure 3–77. Steel roof joists, with missing roof decks, remained connected 

to CMU bond beam. Bond beam remained continuous, but was disconnected 

from the CMU walls along the bond line between the two CMU courses at the 

top of the Franklin Technology Center wall. 

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Figure 3–78. Perimeter CMU wall that collapsed after loss of roof lateral bracing at the 

Franklin Technology Center (note lack of reinforcing dowels connecting wall to concrete 

footing). 

Figure 3–79. Another perimeter wall failure at the Franklin Technology Center (note lack of reinforcing dowels connecting wall to concrete footing). 

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	 Almost all of the perimeter CMU walls collapsed. It should be noted that while the walls 

were partially grouted and reinforced, as specified in the available design information for the 

1978 south–half addition, close inspection on May 25, 2011, found that there were wall 

sections (especially in the original 1960s north half) that had no or minimal structural 

connection between the wall and the RC foundation103 (see Fig. 3–78 and 3–79). 

There were no reported fatalities or injuries that occurred as a result of the complete structural collapse of 

the Franklin Technology Center. The facility was closed and there were no occupants at the time the May 

22, 2011, Joplin tornado struck. 

3.2.1.7 St. Mary’s Catholic Elementary School 

St. Mary’s Catholic Elementary School was a typical short–span, one–story BTS building with lightly 

reinforced CMU perimeter walls laterally braced by single–span steel roof systems (open–web steel roof 

joists supporting wide–rib steel roof decks), similar to the Franklin Technology Center. It was located 

approximately 100 ft north of the estimated center of the tornado damage path. Fig. 3–80 shows an 

overview of the facility, which sustained complete collapse. The estimated maximum wind speed that 

affected the buildings of St. Mary’s Catholic Elementary school was about 170 mph ± 45 mph from a 

westerly direction (EF–4 range, similar to the wind speed range estimated for Joplin High School; see 

Fig. 3–81). 

The facility consisted of connected building sections, including a section that was built prior to 1994 and 

an addition built in 1994. NIST was able to obtain only a partial set of the design drawings for the 1994 

addition, which showed the following design details for the two primary structural components of the 

buildings: 

	 Steel Roof System: The roof system consisted of short, single–span, open–web steel roof 

joists supporting 11⁄2 in., wide–rib, 22–gauge, three–span continuous steel roof decks covered 

by 3 in. thick rigid insulation and a single layer of asphalt roof covering. 

	 Perimeter CMU Walls: The walls consisted of three layers: an interior structural layer (load 

bearing) of CMU; a middle layer of 2 in. rigid insulation; and an outer layer of brick veneer. 

Available drawings for the 1994 addition show that the walls of the addition sections were 

vertically reinforced with #4 reinforcing bars. The top course of the CMU was grouted and 

reinforced horizontally with two #4 reinforcing bars to form a bond beam at the top of the 

perimeter walls. The ends of the roof joists were welded onto steel joist seats that were 

anchored into the CMU bond beam with steel stud anchors. 

The building sustained complete structural collapse similar to that typically observed for this type of 

construction when it is subjected to strong wind uplift action: 

103 This is not inconsistent with standard practice. Friction-only connections between walls and footings are accepted for regions 

with low or no seismic risk. Rotational stability is to be provided for the wall by temporary bracing during the construction phase 

(prior to connection to the roof system) and by lateral bracing provided by the roof system after connection with the roof. 

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© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 3–80. Overview of damage at St. Mary’s Catholic Elementary School, with estimated center line of tornado damage 

path shown in red. 

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Figure 3–81. Estimated time–history of wind speed and direction 

near the northeast corner of St. Mary’s Catholic Elementary School.

Figure 3–82. Section of building at St. Mary’s Catholic Elementary school with complete 

loss of the steel roof system. 

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Figure 3–83. Section of building at St. Mary’s Catholic Elementary school with collapsed 

perimeter CMU walls. 

	 The roof system (roof deck and roof joists) of most of the building sections disconnected 

from the perimeter CMU walls due to the failure of either roof deck–to–joist connections 

(failure of puddle welds) or roof–joist–to–wall connections (vertical load path in the wall was 

not continuous vertically, with the mortar joint between the top bond beam and the next CMU 

course being the weak link, and the bond beam, while remaining continuous horizontally, 

disconnected from the remainder of the perimeter walls under wind uplift action; see Fig. 3–

82). 

	 Almost all of the perimeter CMU walls collapsed due to the loss of the roof (and sole lateral 

bracing) system (see Fig. 3–83). 

There were no reported fatalities or injuries that occurred as a result of the complete structural collapse of 

St. Mary’s Catholic Elementary school.

3.2.1.8 Summary of Performance of Critical Facilities and High–Occupancy Buildings 

The followings are findings that pertain to the performance of critical facilities and high–occupancy 

buildings during the May 22, 2011, Joplin tornado. Several of the findings listed below are also 

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consistent with findings regarding responses of critical and institutional facilities during the May 20, 

2013, tornado in Moore, Oklahoma (NIST, 2013): 

	 Buildings in general, including the NIST–surveyed critical facilities and high–occupancy 

buildings described in the above section, are not designed to withstand tornado hazards (extreme 

wind speeds and windborne debris), and accordingly there are no building code requirements for 

such hazards. Most buildings in the area damaged by the May 22, 2011, Joplin tornado, were 

subjected to wind speeds that well exceeded the non–tornadic wind design requirements of the 

building codes applicable to them. Windborne debris contributed significantly to building 

damage, and is also not considered as a hazard in building design. 

	 Surveyed critical facilities (SJRMC) and high–occupancy buildings (Walmart, Home Depot) 

were not able to provide life safety protection to occupants. 

	 Engineered buildings of affected critical and high–occupancy facilities surveyed by NIST that 

had a lateral load resisting system that did not depend on bracing from the roof system for lateral 

stability (such as steel and concrete moment frame buildings) withstood the tornado without 

structural collapse. Those that relied on a roof diaphragm of reinforced concrete or composite 

concrete and steel deck (such as steel braced frame buildings with that type of roof) also 

withstood the tornado without structural collapse. Those that relied on the bracing of a less 

robust, light weight steel roof system for lateral stability (such as Box–Type System (BTS) 

buildings) were prone to structural collapse. 

	 Structural collapse of NIST–surveyed BTS buildings of critical and high–occupancy facilities 

began with failure of the roof system due to wind uplift (failure of roof deck–to–joist or joist–to–

wall connection), leading to loss of lateral bracing for perimeter walls and causing them to 

collapse by rotation at the base due to lateral load. Available design information showed the roof 

connections of these buildings to be adequate for code–level design wind pressures, making it 

unlikely that these buildings would have failed at code–level winds. 

	 NIST–surveyed BTS buildings that sustained total structural collapse have two common design 

features that increase their vulnerability to collapse in a tornadoes: 

- Long span, light–gage steel roof systems, and 

- Friction–only wall–to–footing connection (currently accepted practice for areas with low or 

no seismic risk) 

	 All NIST–surveyed engineered buildings of affected critical and high–occupancy facilities 

sustained significant damage to the building envelopes and interior due to the combination of 

wind pressure, impact of windborne debris, and the subsequent water intrusion. 

	 Failure of the envelopes of buildings at SJRMC, leading to loss of protection and subsequent 

extensive damage of the building interior (including electrical distribution and fixtures, water and 

gas pipes, HVAC system and ductwork, elevator system and elevator shaft enclosure), was the 

primary cause for the complete loss of functionality of this critical facility, despite the robust 

structural system that could withstand the tornado without structural collapse. 

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	 The majority of impact–resistant windows on the fifth floor (Behavioral Health Unit) of the West 

Tower of SJRMC remained intact, whereas most regular dual pane insulated windows at SJRMC 

were broken when exposed to the same tornado hazards. 

	 While there was no direct evidence that roof aggregates contributed to any injuries or fatalities in 

Joplin, there was evidence that roof aggregate contributed to envelope damage of SJRMC’s

buildings and surrounding structures, thus adding to the tornado debris hazard and the potential 

for injuries or fatalities. 

3.2.2 Commercial Buildings 

3.2.2.1 Ozark Center for Autism 

The Ozark Center for Autism, located at 2411 South Jackson in Joplin (Ozark Center), was approximately 

300 ft north of the estimated center of the tornado damage path (also about 300 ft to 350 ft northwest of 

the demolished Greenbriar Nursing Home; see Fig. 3–1 in Sec. 3.1.2 and Fig. 3–84 below). The building 

was affected by a maximum wind speed estimated at approximately 165 mph ± 45 mph (EF–3 to EF–4 

range) from a westerly direction and, while it did not collapse structurally, sustained significant damage 

to the building envelope and interior. Figure 3–85 shows the estimated time–history of the wind speeds 

that affected the Ozark Center. 

The building comprised two rectangular sections: Main and Physical Education (PE). The Main section, 

153 ft 8 in.  49 ft 8 in. in plan and oriented in the north–south direction, was a three–story CIP RC 

braced frame structure. The PE section, also rectangular with a 65 ft 4 in.  74 ft plan dimension, was a 

two–story steel moment frame structure supporting a steel roof system (open–web steel joists and wide–

rib steel deck panels). The PE section was connected to the east wall of the Main section. It is unknown 

when the building was first designed and constructed, but it was remodeled in 2007. The remodeling 

involved changes in interior layout with removal of old partition walls and addition of new ones. NIST 

was able to obtain a partial set of architectural drawings for the 2007 remodel. The sections below 

summarize the design, damage, and performance information relating to this building. 

Design Information: 

	 Year Built: Original building, unknown; remodeled in 2007. 

	 Building Code: Remodeled based on IBC 2000. 

	 Design Parameters: 90 mph basis design wind speed. 

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© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 3–84. Overview of damage to the Ozark Center and surrounding buildings, with estimated center line of tornado 

damage path shown in red. 

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Figure 3–85. Estimated time–history of wind speed and direction
 

near the southwest corner of the Ozark Center.
 

	 Structural System: 

	 Main Section: The MWFRS was a three–story CIP RC braced frame, comprising (1) 

square RC columns (two exterior column lines and two interior column lines in the 

north–south direction, dividing the building into 3 bays in the east–west direction) 

supporting (2) perimeter deep RC spandrel beams and (3) RC flat slabs for floors and 

roof. The frame was braced by an RC shear wall (on the east elevation, bracing in the 

north–south direction) as well as by CMU walls surrounding the stairwell (bracing in the 

east–west direction). See Fig. 3–86. 

	 PE Section: The MWFRS was a two–story steel moment frame supporting steel trusses 

and open–web steel roof joists that were covered by wide–rib steel roof decks (see Fig. 

3–87). 

	 Building Envelope: 

	 Main Section: Vertical envelope consisted of (1) CMU infill walls between exterior 

columns, cladded with I–shaped steel furring strips that provided backing surfaces for 

light–gauge exterior steel panels, and (2) dual–pane insulating windows on all four 

elevations. Roof envelope was a CIP RC slab, covered with a mixture of hot asphalt and 

gravel. 

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Physical 

Education Section 

Main Section 

Shear Wall 

Source: FEMA MAT. 

Figure 3–86. Ozark Center building (viewed from the southeast). 

Figure 3–87. Interior view of the physical education section of the Ozark Center showing 

structural system with roof truss–column moment connection and open–web roof joist 

and wide–rib steel roof deck. 

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	 PE Section: Vertical envelope consisted of brick infill walls for the first story and 

insulating glass windows with steel framing for the second story. Roof envelope 

comprised wide–rib steel roof decks, covered with a single layer of thermal insulation, 

and ballasted with a hot asphalt and gravel mixture (the gravels were not loose–laid). 

	 Other Feature: The Ozark Center building had two designated “Areas of Refuge” located in 

the stairwells of the Main section of the building (see Sec. 3.3.3.1). 

Damage and Performance Information: 

The building sustained significant damage to the building envelope, and subsequently significant damage 

to all electrical/HVAC/plumbing systems and contents in the building interior. However, there was no 

apparent damage to the MWFRS of the Main section (CIP concrete braced frame) and only minor damage 

to MWFRS of the PE section (steel moment frame), despite the building’s close proximity to the center of 

the tornado damage path and the wind infiltration allowed by the breached envelope (causing increased 

wind uplift pressure). As a result, neither section of the building collapsed structurally, but the entire 

facility sustained complete loss of operation. The damage to the building envelope included: 

	 Loss of part of the roof system (steel roof decks only, not the supporting roof joists) and all 

vertical envelopes (insulating windows and window frames) on all three wind–exposed sides 

of the PE section due to wind uplift pressure (disconnection and loss of steel roof decks, see 

Fig. 3–88). 

	 Damage to or loss of all vertical envelopes on all four wind–exposed sides of the Main 

section, including failures of all light–gauge exterior steel panels and window glass glazing 

(see Fig. 3–89). 

The minor structural damage involved deformation of the perimeter steel beam at the northeast corner of 

the PE section (see Fig. 3–88). This was likely due to debris impact and resulted in no significant 

reduction to the lateral load capacity of the MWFRS of this section. 

The overall performance of the Ozark Center building (damage to building envelope, but no damage to 

the MWFRS despite wind pressure exceeding design conditions, resulting in complete loss of 

functionality) is very similar to the performance observed for RC and steel frame buildings elsewhere 

(e.g., the towers and medical office buildings of SJRMC (see Sec. 3.2.1.1)). 

As indicated above, the building had two designated areas of refuge located in the stairwells protected by 

CMU wall enclosures (see Sec. 3.3.3.1). NIST does not have information regarding occupancy at the 

time of the May 22, 2011, Joplin tornado, so it is not known whether there were survivors in the building. 

There were no fatalities reported at this building as a result of the tornado. 

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Figure 3–88. Significant damage to the envelope and minor damage to the MWFRS of the 

physical education section of the Ozark Center building, including (1) loss of part of steel 

roof decks, (2) loss of all insulating windows and steel frames on all wind–exposed 

sides, and (3) deformation of steel beam (likely due to debris impact). 

Figure 3–89. Typical damage to the Ozark Center building envelope (broken window 

glazing, missing window frames, and torn exterior steel panels). 

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3.2.2.2 St. Paul’s United Methodist Church 

St. Paul’s United Methodist Church, located at 2423 West 26th Street, was at the periphery of the heavy 

damage path. The southernmost portion of the facility was about 700 ft north of the estimated center of 

the tornado damage path (see Fig. 3–90), and was affected by an estimated maximum wind speed of about 

125 mph ± 35 mph (EF–2 range) from a west–northwesterly direction (see Fig. 3–91). 

The church comprised several light SF buildings, including the MBS at the southernmost portion of the 

facility that was used as the Mass Hall. It was this building that sustained the most significant damage 

during the May 22, 2011, Joplin tornado, while the other buildings sustained mostly minor damage. 

NIST conducted a damage survey of the Mass Hall to study the performance of this type of construction 

(MBS) under tornado hazards. Due to the unavailability of design information for the church buildings, 

the performance information below is based exclusively on engineering information collected during the 

field damage survey conducted shortly after the May 22, 2011, Joplin tornado. 

Metal building systems are designed to the same codes and standards as other forms of construction. The 

primary difference is with the framing methods used and more efficient optimization of materials used. 

Metal building systems typically consist of sets of primary rigid steel frames in the transverse direction. 

Members of the primary frames (columns and rafters) are typically designed with tapered built-up plate 

sections with the most steel in the areas of highest stress. The design of the tapered members to the code 

prescribed loads typically results in lighter overall systems through steel usage that is more efficient than 

in conventional steel construction. These members are field bolted using bolted end plate connections for 

ease of erection. Adjacent primary frames are braced diagonally in the roof and vertical planes using steel 

cables or rods. Portal frames are also sometimes used in side walls instead of steel cables or rods. 

Secondary members, including roof purlins and wall girts, are typically light-gauge, cold-formed Z- or Cshaped cold-formed members. Metal building systems are mostly one-story buildings, but can have two 

stories and often have full or partial mezzanines. 

The metal building system Mass Hall building of St. Paul’s United Methodist Church consisted of five 

sets of primary rigid frames (4 bays), each made of tapered built-up steel columns and rafters joined by 

bolted connections. The frames were braced with steel cables and supported cold-formed Z-shaped 

purlins and a light-gauge standing seam roof that was attached to the purlins with clips that permit 

expansion and contraction of the roof. The clips were attached to the purlins with screws. The cable 

braced primary frames represented the MWFRS of the building. The end frames were somewhat lighter 

than the interior frames, probably because they were designed for half of the end bay loads. The end 

walls were framed with vertical spanning steel studs between tracks that were attached at the bottom to 

the slab and at the top to a channel cap on the top flange of the end frame rafter. The walls were clad 

with steel sheets fastened with screws to horizontal members spanning on the outside of the studs. The 

framing and connections are clearly visible in Fig. 3–92, 3–93, and 3–94. 

The building sustained significant damage to the envelope (disconnection and loss of the standing seam 

roof and all vertical sheet steel wall panels, as well as the collapse of a large part of the steel-stud framing 

on the end walls), but only limited damage to the MWFRS (braced primary rigid frames). As a result, the 

building did not collapse, but sustained complete loss of functionality due to the loss of the envelope and 

subsequent damage to the building interior. The design and construction of the end walls are of most 

interest, as it appears the failure was initiated by a fairly catastrophic loss of them. Because of the type of 

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© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 3–90. Overview of damage at St. Paul’s United Methodist Church and surrounding areas, with the 

estimated center line of the tornado damage path shown in red. 

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Figure 3–91. Estimated time–history of wind speed and direction 

near the Mass Hall of St. Paul’s United Methodist Church.

Figure 3–92. View from east of the damaged, MBS Mass Hall building of St. Paul’s United
 

Methodist Church.
 

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Figure 3–93. Tapered rafter sections with bolted connection and roof purlins of St. Paul’s 

United Methodist Church.
 

Figure 3–94. Damage to envelope of St. Paul’s United Methodist Church. 

construction of the endwalls (steel-stud framing), it is unlikely that this was designed and supplied by the 

metal building manufacturer, as it is not the common way they would frame it (i.e. horizontal Z-shaped 

girts). A judgment on the adequacy of the endwall design and construction cannot be made without 

further investigation, however this is a good reminder that the proper coordination of design responsibility 

on a metal building project is very important. The metal building manufacturer is responsible for what 

178 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

they design and fabricate, but parts of the structure not furnished by the metal building manufacturer 

should be designed by an engineer of record who also ensures adequate interface and proper load path 

into the metal building structure. Another observation of note is that the standing seam roof failure 

resulted from a pullout of the clips from the seams. The clips remained attached to the purlins. This is 

not unusual after an extreme wind event (especially after the major loss of a wall and resulting increase in 

the internal pressure) but it does clearly identify the limit state that was exceeded in the standing seam 

roof design. 

3.2.2.3 Ramesh Shah Ophthalmology Center 

The Ramesh Shah Ophthalmology Center building, located at 1703 West 30th Street, was about 1,500 ft 

south of the estimated center of the tornado damage path and approximately 500 ft southwest of SJRMC. 

The building was at the southern periphery of the swath of heavily damaged areas (see Fig.3–95). The 

time–history of wind speed estimated from the wind field model (see Fig. 3–96) indicated that the 

Ramesh Shah building was affected by a maximum wind speed of 110 mph ± 35 mph (EF–1 to EF–2 

wind speed range), which is close to or just above the wind speed that the structure should have been able 

to resist without collapse or major damage. 

NIST was able to obtain partial design information for this building. These data, combined with damage 

information obtained from NIST’s field survey following the tornado, indicated that the Ramesh Shah 

building was a two–story structure built in 1993 with a plan dimension of 53.6 ft  60 ft. The MWFRS 

consisted of braced primary rigid frames, similar to that used in a metal building system, but this 

particular building was a hybrid of several forms of construction. The first story (partially below ground) 

had 12 in. RC exterior walls. The second story, at ground level, was a steel rigid frame building, with one 

primary frame made of tapered steel columns and rafters at the center of the building (similar to St. Paul’s

United Methodist Church), and two perimeter frames made of I–shaped columns and C–shaped, cold–

formed steel beams. The frames supported a roof system that consisted of cold–formed, Z–shaped steel 

roof purlins covered with standing–seam steel roof decks. The first floor consisted of open–web K series 

bar joists supporting a composite RC floor (3 in. thick) on steel decks. The three rigid frames of the 

second story were diagonally braced with steel cables in the roof plane. See Fig. 3–97, 3–98, and 3–99. 

The steel columns were cast and anchored into the top of the RC wall of the first story (see Fig. 3–100). 

The building vertical envelope consisted of synthetic stucco siding over rigid insulation and combinations 

of tempered and dual–pane insulating window glazing. The roof envelope was standing–seam steel roof 

decking. 

As most of the first story of this building was below ground (and shielded from significant wind effects), 

it was the second story that was most affected by the tornado. Similar to the performance of the Mass 

Hall building of St. Paul’s United Methodist Church the second story of the Ramesh Shah building 

sustained significant damage to its envelope (disconnection and loss of all standing–seam steel roof 

decks, all synthetic stucco siding, and the window glazing and frames), but only limited damage to the 

MWFRS (braced primary rigid frames). The complete loss of the roof and wall envelopes likely relieved 

the pressure on the primary frame members, allowing them to remain standing during the tornado. As a 

result, the MWFRS of the building did not collapse, but the building sustained a complete loss of 

functionality due to the loss of the envelope and subsequent significant damage to the interior. NIST does 

not have information regarding occupancy at this building during the May 22, 2011, Joplin tornado. 

There were no reported fatalities or injuries at this building due to that tornado. 

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© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 3–95. Overview of damage at the Ramesh Shah Ophthalmology Center, with the estimated center line of the tornado 

damage path shown in red. 

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Figure 3–96. Estimated time–history of wind speed and direction 

near the west side of the Ramesh Shah Ophthalmology Center. 

Figure 3–97. Ramesh Shah Ophthalmology Center viewed from the southwest. 

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Figure 3–98. Ramesh Shah Ophthalmology Center viewed from the east–southeast. 

Figure 3–99. Close up view of the Ramesh Shah Ophthalmology Center showing 

connections and cable bracing of the steel frames. 

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Figure 3–100. Close up view of the Ramesh Shah Ophthalmology Center showing 

connection between the steel frame with the concrete wall below. 

3.2.2.4 Summary of Performance of Commercial Buildings 

The followings are findings that pertain to the performance of commercial buildings during the May 22, 

2011 Joplin tornado: 

	 Buildings in general, including the NIST–surveyed commercial buildings described in the above 

section, are not designed to withstand tornado hazards (extreme wind speeds and windborne 

debris), and accordingly there are no building code requirements for these hazards. Most 

commercial buildings in the area damaged by the May 22, 2011, Joplin tornado, were subjected to 

wind speeds close to or greater than the ultimate wind–resisting capacity anticipated in the 

building codes applicable to them. Windborne debris contributed significantly to building 

damage, and is also not considered as a hazard in building design. 

	 Engineered commercial buildings surveyed by NIST that had a lateral load resisting system that 

did not depend on bracing from the roof system for lateral stability (such as steel and concrete 

moment frame buildings) withstood the May 22, 2011, Joplin tornado without structural collapse. 

Those that relied on the bracing of a light steel roof system for lateral stability (such as Box–Type 

System (BTS) buildings) were prone to structural collapse. 

	 MBS commercial buildings surveyed by NIST sustained significant damage to their envelope, but 

no structural collapse of the primary rigid steel frame. 

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3.2.3 Residential Buildings 

The residential buildings in the tornado–affected area were primarily of wood–frame or combinations of 

lightly reinforced CMU and wood–frame construction. The overall performance of residential buildings 

in Joplin during the May 22, 2011, tornado, especially the one– and two–family residential constructions, 

was similar to that typically observed in other tornadoes. That is, it was primarily a function of two 

factors: proximity to the tornado; and the quality of construction. However, even among buildings in the 

same area (i.e., with similar proximity to tornado hazards) with similar construction quality, degrees of 

damage can vary significantly due to changes in the tornado’s intensity as it moves through the area. 

Given that there were 7,411 residential buildings that were either damaged or destroyed in the May 22, 

2011, Joplin tornado, it was not practical to review the performance of all single–family residential 

structures. Consequently, NIST’s approach was to review the performance of a few selected multi–family 

residential buildings in detail (Greenbriar Nursing Home and Mercy Village Apartments), and review the 

performance of single–family homes in a general, statistical context. The aim was to make representative 

observations that might be useful for the development of best practices and future design strategies for 

more tornado–resistant residential construction. 

As was discussed in Sec. 3.1.5, given the City of Joplin’s history of timely and proactive code adoption 

and enforcement, it is reasonable to assume that both the older and more recently constructed residential 

buildings in Joplin were built in accordance with the building codes then in effect (since 2003, the codes 

in use have been the 2000 ICC International Residential Code for One– and Two–Family Dwellings 

(IRC) for one– and two–family homes and the 2000 IBC for multi–family residential buildings). These 

building codes have provided prescriptive guidance that can be described as component–based (rather 

than system–based) for framing individual roofs and walls (e.g., stud spacing, nailing schedules, bracing 

or sheathing materials for in–plane shear), constructing roof–to–wall connections (e.g., use rafter or truss 

tie–downs with prescribed strength for roof assemblies subject to wind uplift pressure which, by default, 

could be satisfied using common nails in regions with 90 mph wind), and designing wall–to–foundation 

connections (e.g., use sill plates anchored by bolts into slab/foundation at 6 ft spacing). Current codes 

also stipulate that “a continuous load path shall be provided to transmit uplift forces from the rafter and 

truss ties to the foundation,” but provide no specific guidance on how this is to be achieved. 

Figures 3–1, 3–2, and 3–3 depict the levels of damage sustained by all buildings affected by the May 22, 

2011, Joplin tornado, including residential structures, based on the Pictometry® database (color codes for 

damage conditions following building damage classification used by FEMA, which include green (light 

damage), yellow (medium damage), orange (heavy/totaled), and red (demolished)). As can be seen from 

these figures, the damage tends to be more severe for residential buildings closer to the estimated center 

of the tornado damage path. Table 3–5 shows a general correlation between the age of residential 

buildings, which were divided into three age groups (before 1950, 1950–2000, and 2001–present) and the 

four damage conditions. 

As shown in Table 3–5 above, 43 percent (3,069) of the 7,131 residential buildings affected by the May 

22, 2011, Joplin tornado sustained damage classified as heavy/totaled or demolished. This percentage did 

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Table 3–5. Distribution of tornado–affected residential structures by level of damage 

sustained and year built. 

Year Built Level of Damage Total 

% of Total Rated as 

Heavy/Totaled or 

Light Medium Heavy/Totaled Demolished Demolished 

Before 1950 1616 289 426 863 3194 40.4 

1950–2000 1569 375 617 1070 3631 46.5 

2001–Present 175 38 39 54 306 30.4 

All Years 3,360 702 1,082 1,987 7,131104 43 

not vary significantly among the age groups, so there was no discernible relationship between the level of 

damage sustained and the age of the structure. Thus, it can be said that both older and newer residential 

structures performed similarly during the Joplin tornado. 

Following are general descriptions of the classifications used for residential damage: 

	 Light: Visible damage to building envelope, including loss of small portion of roof covering. 

	 Medium: Loss of small portion of roof system, including roof covering and roof structural 

sheathing, and damage to some roof trusses. 

	 Heavy/Totaled: Loss of significant portion of (or entire) roof system, exposing the building 

interior to weather damage and compromising the lateral bracing system for walls, but walls 

remain standing. 

	 Demolished: Roof and walls collapsed; entire structure might be shifted off of the foundation 

and collapsed. 

An illustration of how homes in a small neighborhood were classed is provided in Fig. 3–101. The 

performance of selected multi–family buildings is discussed in Sec. 3.2.3.1. General observations on the 

typical performance of single–family residential structures are presented in Sec. 3.2.3.2. 

3.2.3.1 Multi–Family Residential Buildings 

There were several multi–family residential buildings that were affected by the May 22, 2011, Joplin 

tornado. NIST selected for damage surveys two properties that were representative of the types of 

construction and damage found among this group of facilities: Greenbriar Nursing Home105 and Mercy 

Village Apartments. 

104 There were 280 damaged residential buildings that had no age information. The total number of residential buildings that 

sustained tornado damage was 7,411 (7,131 + 280). 

105 Nursing homes are regulated as healthcare occupancies under the building code, however, the materials and methods of 

construction at this facility were similar to that of multi-family residential construction. 

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Aerial Image © 2011 

GeoEye. Building 

footprint data 

Pictometry®. Used 

with permission. 

Enhancements by 

NIST. 

Figure 3–101. References for Pictometry® database damage classifications and coding: 

light (green), medium (yellow), heavy/totaled (orange), and demolished (red). 

Aerial Image © 2011 GeoEye. Used with permission. Enhancements by NIST. 

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Even though the Greenbriar Nursing Home was a health care facility by function (and thus could also 

have been discussed among the critical facilities and high–occupancy buildings addressed in Sec. 3.2.1), it 

is discussed here because of its construction type, which was typical of multi–family residential 

construction in the Joplin area. The Greenbriar Nursing Home was an unreinforced CMU wall structure 

with sheathed wood roof trusses. The Mercy Village Apartment building was a platform framed 

construction with 2  4 wood frames, wood floors, and wood roof trusses. These two buildings also 

represented the two ends of the damage spectrum; the Greenbriar Nursing Home was completely 

demolished while Mercy Village sustained only minor envelope damage. Descriptions are provided 

below of the design of these two buildings, the environmental conditions that affected them on May 22, 

2011, and their performance. 

Greenbriar Nursing Home—

The Greenbriar Nursing Home, located at 2502 South Moffet Avenue (in the same vicinity as the Ozark 

Center and St. Mary’s school) (Greenbriar), was at the center of the estimated tornado damage path (see 

Fig. 3–102). The facility was constructed in the mid–1960s, likely based on either BOCA BBC/1960 or 

1965, and comprised a rectangular core section, oriented in the east–west direction that was connected to 

four rectangular wing sections oriented in the north–south direction. The maximum wind speed affecting 

this facility, estimated based on wind field model results for a point just to the west of the building, was 

about 170 mph ± 45 mph (EF–4 range, see Fig. 3–103). The Greenbriar was directly east (downstream) 

of several residential neighborhoods that were totally demolished (see Fig. 3–1and 3–102). Due to this 

juxtaposition, the Greenbriar Nursing Home was likely affected by significant amounts of wind–borne 

debris in addition to the strong tornado wind speed. The entire facility (core and four wing sections) 

collapsed completely in the storm. 

NIST surveyed this facility but was unable to obtain any design information. Information from the on– 

site survey indicated that the building had one story, was made primarily with unreinforced (or very 

lightly reinforced vertically) CMU exterior walls supporting wood roof trusses, and did not have a 

basement. The roof trusses, sheathed with 4  8 plywood panels and covered with standing–seam, light– 

gauge steel roof covering, were connected to the top of the CMU walls by common nails driven into a 2x 

wood top plate. The unreinforced CMU walls were minimally connected to the concrete footing.106 This 

type of construction, with minimal or no vertical reinforcement within the CMU walls, was vulnerable to 

damage by wind uplift action due to the lack of continuity in the vertical load path. The building interior 

was partitioned into multiple units for long–term housing of patients with non–load–bearing 2  4 wood 

frames. NIST does not have information regarding whether any areas in the building were formally 

designated as refuge areas prior to the tornado. The damage survey indicated that there were no areas in 

the interior of the facility that were structurally hardened and therefore more suitable than other areas for 

use as designated safe or refuge areas. 

Figures 3–104, 3–105, and 3–106 show different views of the damage at Greenbriar Nursing Home, 

which included: 

	 Disconnection and complete loss of all roof systems in all building sections (core and four 

wings), with the 2  4 wood roof trusses, 4  8 plywood sheathing, and all standing–seam 

106 This is not inconsistent with standard practice. Friction-only connections between walls and footings are accepted for regions 

with low or no seismic risk. 

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© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 3–102. Overview of the Greenbriar Nursing Home, shown in relation to the estimated center line of the tornado 

damage path (red line). 

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Figure 3–103. Estimated time–history of wind speed and direction 

near the east side of the Greenbriar Nursing Home. 

Figure 3–104. Collapsed Greenbriar Nursing Home (viewed from the east) with 

missing roof system and collapsed exterior CMU walls. Note debris from 

building materials as well as other sources (automobiles) in all interior areas 

of the facility. 

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Figure 3–105. Collapsed Greenbriar Nursing Home. 

Figure 3–106. Collapsed Greenbriar Nursing Home (viewed from the north) 

showing the portion of the north wing’s exterior wall that did not collapse. 

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steel roof coverings disintegrated into small pieces (this further contributed to the wind–borne 

debris hazard, in contrast to steel roof joist systems, where the joists may have gotten 

disconnected from the wall but in general stayed together as a unit). A significant amount of 

the roof and building debris either fell into the building interior or scattered around the 

vicinity of the facility. 

 Complete collapse of almost all the exterior CMU walls, except for a few small sections 

along the north ends of the north wings. The collapsed CMU walls mostly disintegrated into 

either individual CMU blocks or very small clusters of a few CMU blocks (reflecting the lack 

of within–wall reinforcement). 

As shown in the figures, the interior of the entire facility was covered with building materials and other 

wind–borne debris, which presented an extremely hazardous environment to the occupants on May 22, 

2011. As discussed in Chapter 4, there were 19 fatalities (mostly impacted–related), out of a total of 

approximately 95 occupants, at the Greenbriar as a result of the tornado and structural collapse. 

Reportedly, many of the patients were placed in the hallway at the center of the east–west core section of 

the facility. This was in order to keep them as far away from the windows as possible. While this was the 

only logical option, the inner hallway of this facility was structurally no different from any other areas 

within the facility, and the general construction of the Greenbriar building, with its lack of continuity in 

the vertical load path, offered little protection against the direct impact of the May 22, 2011, Joplin 

tornado. 

Mercy Village Apartments—

Mercy Village Apartments, located at 1148 West 28th Street in Joplin, was approximately 1,200 ft south 

of the estimated center of the tornado damage path and about 1,000 ft directly east of the south complex 

of SJRMC. It was at the southern periphery of, but not in close proximity to, the demolished residential 

neighborhoods to its northeast and therefore was likely to have been affected to a lesser degree by wind– 

borne debris impacts compared with the Greenbriar Nursing Home (see Fig. 3–107, note the undamaged, 

green vegetation immediately south of the building, which indicated lower wind speed and less severe 

tornado hazards in the vicinity of Mercy Village Apartments). The estimated maximum wind speed that 

affected the Mercy Village Apartments building was about 135 mph ± 40 mph (EF–2 to EF–3 wind 

speed range, see Fig. 3–108). The building was a three–story platform wood–framed structure with an 

elevator, L–shaped plan configuration (18, 216 ft2 footprint and 51.6 ft building height), and a total of 66 

senior living apartment units. The sections below summarize the design, damage, and performance 

information related to this building. 

Design Information: 

 Year Built: 2003. 

 Building Code: 2000 IBC. 

 Design Parameters: Basic wind speed, 90 mph; exposure category, C; importance factor, 1.0. 

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© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 3–107. Overview of the Mercy Village Apartments, shown in relation to the estimated center line of the tornado 

damage path (red line). SJRMC is located to the west (left) of the apartments. 

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Figure 3–108. Estimated time–history of wind speed and direction
 

near the northeast corner of the Mercy Village Apartments.
 

	 Structural System: 

	 Roof System: 2  4 wood roof trusses sheathed with plywood panels. The ends of each 

roof truss were connected to the top board of the double top plate of the third–floor 

exterior bearing walls with hurricane tie–downs (generally referred to as “hurricane 

clips,” see Fig. 3–109). Note that the hurricane tie–downs are installed on the inside of 

the wall while the sheathing that provides the transfer of loads to the wall studs is located 

on the outside of the wall. Hurricane tie–down manufacturer data suggests that this 

configuration reduces the effectiveness of the hurricane tie–downs by 50 percent unless 

straps are added to the inside of the wall framing to tie the double top plate to the wall 

studs. 

	 Walls: 

 First–floor exterior load–bearing walls: wood frame with double 2  4 studs at 16 in. 

on center. 

 Second– and third–floor exterior load–bearing walls: wood frame with single 2  4 

studs at 16 in. on center. 

All exterior load–bearing walls were braced with structural sheathing (7/16 in.  4 ft 

wide structural plywood panels attached with 8d common nails) and diagonal steel 

straps on the outside face, and 5/8 in. gypsum wallboard on the inside face. In 

addition to the required fastening with common nails, the exterior load–bearing walls 

NIST NCSTAR 3, Joplin Tornado Investigation 193 
 

 

 

 

 

 

 

 

 

 

 

 

 

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Figure 3–109. Hurricane tie–downs connecting wood roof trusses to
 

load–bearing wood–frame wall at the Mercy Village Apartments.
 

below and above the second and third floors were tied to the floor trusses between 

them using pre–loaded hold–downs (Simpson PHD2–SDS3 hold–downs) and steel 

straps. And the first–story walls were secured to the concrete foundation with 1⁄2 in. 

diameter  4 in. embedment adhesive anchors at 32 in. on center. The hurricane roof 

tie–downs, pre–loaded wall hold–downs, and embedment foundation anchors 

provided a structural wood–frame system with a continuous vertical load path (see 

Fig. 3–110). 

	 Floor: 18 in. deep wood floor trusses spaced at 16 in. on center with 3⁄4 in. plywood 

subflooring. 

	 Foundation: 4 in. concrete slab and concrete foundation footings of various sizes. 

	 Envelope: 

	 Roof: Asphalt shingles over single–layer bituminous felt over plywood sheathing over 

wood roof trusses. 

	 Walls: Combination of brick veneer and horizontal cement–board lap siding over a wood 

frame. Glazing consisted of both insulating and 1⁄4 in. tempered glass windows on all 

exterior sides. 

194 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

© 2013 Ron Reid. Used with permission. 

Figure 3–110. L to R, pre–deflected wall hold–down, steel strap, and wall anchor at the 

Mercy Village Apartments. 

Damage and Performance Information: 

While the tornado hazards (wind speed and wind–borne debris) that affected the Mercy Village 

Apartments building on May 22, 2011, were estimated to be less severe than those that affected the 

Greenbriar Nursing Home (135 mph ± 40 mph versus 170 mph ± 45 mph, and a less significant wind– 

borne debris field given the surrounding areas and relative proximity to the tornado damage path; see Fig. 

3–107), these hazards still exceeded the conditions that the building was designed to resist (90 mph basic 

wind speed, corresponding to roughly 115 mph ultimate wind speed, with no provisions for wind–borne 

debris impact). Despite these hazards, the damage at Mercy Village Apartments was limited mostly to the 

building envelope, with relatively light damage to the structural system that included loss of a small 

portion of the roof framing system and two load bearing walls at the south and east ends being pushed 

slightly out of plumb (at wind speeds in this range, strong wood–frame structures have been observed to 

have their roof system either severely damaged or completely disconnected due to wind uplift). This 

relatively good structural performance can probably be attributed in part to the use of more robust 

connections, typically required only for residential wood–frame buildings in hurricane–prone regions, 

between the primary structural systems of the building (roof–to–wall, wall–to–wall between floors, and 

wall–to–foundation, thus ensuring continuity of load path from roof to foundation). The damage to the 

building envelope, shown in Fig. 3–111, and to the envelope and structural system of the Mercy Village 

building, shown in Fig. 3–112, included: 

 Damage to window glazing on all sides of the building (both insulating glass and tempered 

glass), likely due to wind–borne debris impacts (there were windows near the broken 

windows that were not damaged, suggesting that wind pressure was likely not the cause of 

the broken windows). 

 Damage to the exterior brick veneer, cement–board sidings (missing, broken boards), and 

roof covering (lost roof shingles). 

NIST NCSTAR 3, Joplin Tornado Investigation 195 
 

 

 

 

 

 

 

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Chapter 3 

Figure 3–111. Mercy Village Apartments, viewed from the north, with envelope and roof 

framing and sheathing damage (sidings, window glazing, roof covering). 

© 2011 Ben Ross SAVE. Used with Permission. 

Figure 3–112. Damage to the building envelope and structural systems (loss of wall 

section, roof framing and sheathing) of the Mercy Village Apartments. 

196 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

	 Loss of entire sections of wall as well as roof sheathing between the third floor and roof (see 

Fig. 3–112). 

	 Reported damage to the interior due to water infiltration where there were damaged windows. 

While it is not known how many occupants were present during the May 22, 2011, Joplin tornado, it is 

known that the facility was occupied. However, there were no reports of fatalities or injuries occurring at 

this building. 

3.2.3.2 Single–Family Residential Buildings 

The correlations among environmental conditions (in terms of EF polygons), degree of damage (light, 

medium, heavy/totaled, and demolished), and construction age (implicitly construction quality) for the 

residential structures affected by the May 22, 2011, Joplin tornado are shown in Table 3-6. 

Statistics from the table above show that, in general: 

	 Age of construction was not a statistically significant factor in terms of performance of residential 

buildings. In other words, newer and older residential buildings sustained similar degrees of 

damage when exposed to similar tornado hazards. 

	 More than 90% of residential buildings sustained at least heavy/totaled damage when exposed to 

the EF–4 wind speed range. This ratio dropped to more than 80% for residential buildings 

exposed to the EF–3 wind speed range, slightly more than 50% for areas affected by the EF–2 

wind speed range, less than 20% for EF–1 areas, and about 4% for EF–0 areas. These ratios 

suggested that about 50% of residential buildings, built based on current and past building codes, 

would be able to survive an EF–2 tornado (with medium damage, at most). The wind speed 

range associated with an EF–2 tornado is 111–135 mph (in 3 second gusts), which is close to or 

above the wind speed that would be expected to cause failure of a building designed for the 

current basic design wind speed of 90 mph for tornado prone areas. 

The structural failures observed among residential buildings predominantly involved disconnection of 

component structural systems (roof–to–wall and wall–to–foundation connections), with roof 

disconnections causing most of the damage (see Fig. 3–113 to 3–118). This indicated that structural 

failure tended to be due to a lack of robustness in the connections between residential structural 

components (i.e., the inability to maintain a continuous vertical load path from roof to foundation), rather 

than to the structural capacity within the components. More robust uplift–resistant connections between 

primary structural components can help keep the roof system connected to the supporting walls (and thus 

continuing to provide lateral bracing for the walls, keeping them from collapsing due to lateral wind 

loads) and thereby reduce the severity of damage to individual residential buildings. Keeping more 

affected buildings intact can reduce wind–borne debris, the potential for injuries and fatalities, and overall 

damage, which can enhance a community’s resilience to tornadoes. 

To achieve this improved performance, overall system integrity (i.e., primary structural components of 

residential systems remain connected, albeit damaged) up to a certain wind speed range (for example, a 

maximum wind speed in the EF–3 range), should be stipulated as a required design objective. 

NIST NCSTAR 3, Joplin Tornado Investigation 197 
 

 

 

 

Chapter 3 

Table 3–6. Correlation between degree of damage and age of residential construction, 

by severity of wind speed. 

Residential Buildings in the EF–4 Damage Area 

Year Built Degree of Damage 

Light Medium Heavy/Totaled (H/T) Demolished (D) TOTAL % H/T or D 

Pre–1950 7 4 72 343 426 97.4 

1950–2000 5 18 93 392 508 95.5 

2001–present 0 2 3 15 20 90 

954 

Residential Buildings in the EF–3 Damage Area 

Year Built Degree of Damage 

Light Medium Heavy/Totaled (H/T) Demolished (D) TOTAL % H/T or D 

Pre–1950 42 50 181 273 546 83.2 

1950–2000 32 53 180 403 668 87.3 

2001–present 1 3 9 23 36 88.9 

1250 

Residential Buildings in the EF–2 Damage Area 

Year Built Degree of Damage 

Light Medium Heavy/Totaled (H/T) Demolished (D) TOTAL % H/T or D 

Pre–1950 190 111 110 138 549 45.2 

1950–2000 174 120 207 219 720 59.2 

2001–present 2 6 6 3 17 52.9 

1286 

Residential Buildings in the EF–1 Damage Area 

Year Built Degree of Damage 

Light Medium Heavy/Totaled (H/T) Demolished (D) TOTAL % H/T or D 

Pre–1950 643 95 45 73 856 13.8 

1950–2000 923 183 127 84 1317 16.0 

2001–present 34 7 1 1 43 4.6 

2216 

Residential Buildings in the EF–0 Damage Area 

Year Built Degree of Damage 

Light Medium Heavy/Totaled (H/T) Demolished (D) TOTAL % H/T or D 

Pre–1950 661 18 12 16 707 4.0 

1950–2000 436 15 7 12 470 4.0 

2001–present 45 1 0 0 46 0.0 

1223 

198 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

Chapter 3 

© 2011 GeoEye. Used with permission. Enhancements by NIST.. 

Figure 3–113. Residential failure due to disconnection of entire roof system (roof–to–

wall connection failure due to wind uplift). 

NIST NCSTAR 3, Joplin Tornado Investigation 199 
 

 

 

 

 

Chapter 3 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 3–114. Failure of first–story–to–foundation wall connection. Entire roof and first 

floor shifted off of lower story (directly north of SJRMC). 

200 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

Chapter 3 

Figure 3–115. Disconnection and loss of entire roof system. 

Figure 3–116. Typical 

roof–to–wall connection 

damage. 

NIST NCSTAR 3, Joplin Tornado Investigation 201 
 

 

 

 

 

 

Chapter 3 

Figure 3–117. Typical 

wall–to–foundation 

connections. 

Figure 3–118. 

Typical damage to 

residential dwelling 

envelope. 

202 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

3.3 

Chapter 3 

3.2.3.3 Summary of Performance of Residential Buildings 

The followings are findings that pertain to the performance of residential buildings during the May 22, 

2011, Joplin tornado: 

	 Residential buildings in general are not designed to withstand tornado hazards and accordingly 

there are no building code requirements for them. The majority of residential buildings in the 

area damaged by the May 22, 2011, Joplin tornado, were subjected to wind speeds close to or 

above the speed that would be expected to cause failure of structures designed to the non– 

tornadic wind design requirements of the building codes applicable to them. Windborne debris 

contributed significantly to building damage, and is also not considered as a hazard in residential 

building design. 

	 Of the 161 total fatalities, 135 (or 83.8%) were building–related, and more than half of the 

building–related fatalities (74 of 141, or 52.5%) occurred in residential buildings. Of the 

buildings that were damaged, 7411 were residential and 553 were non–residential. About 43% of 

the residential buildings sustained at least heavy/totaled damage condition. This resulted in 

$1.228 billion in insured losses for non–residential property and $0.552 billion insured losses for 

residential property. 

	 Failure of residential wood–frame buildings predominantly involved failure of the connections 

between structural components, rather than of the components themselves (roof, wall, and floor) 

with the majority of these failures involving disconnection of the roof from the walls and walls 

from the foundation. This indicates lack of robustness in the connections and consequently in the 

continuity of vertical load path from roof to foundation. 

	 Better structural performance in one of the NIST–surveyed multi–story wood frame residential 

buildings in Joplin may be attributed, in part, to a more complete load path from the roof to the 

foundations. 

PERFORMANCE OF DESIGNATED SAFE AREAS AND SHELTERS 

Safe sheltering against tornado hazards requires the availability of hardened physical facilities and an 

effective operating procedure. Hardened facilities can range from stand–alone public shelters or safe 

rooms, which are specially designed and constructed to criteria that are well above the minimum code 

requirements of the national model codes (IBC, NFPA 5000, and IRC) for wind loading, to designated 

areas of refuge within an existing facility that, while not specifically designed and constructed, are 

deemed structurally more suitable than other areas in the facility and are accessible for use by building 

occupants for sheltering. 

Public shelters/safe rooms are typically required to be constructed and operated in accordance with the 

requirements of the local authority having jurisdiction (AHJ). The criteria most often used for 

construction are based on FEMA 361 (2008), Design and Construction Guidance for Community Safe 

Rooms, or the ICC–500 (2008) Standard for the Design and Construction of Storm Shelters. Storm 

shelters/safe rooms built to these special, above–code requirements can offer life–safety protection 

against tornado hazards. 

NIST NCSTAR 3, Joplin Tornado Investigation 203 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

Designated areas of refuge in a facility, also commonly known as “best available refuge areas,” are areas 

within a facility that are likely to offer the greatest protection for occupants from a tornado compared with 

other areas in the facility. These areas are not specifically designed to criteria above the minimum code 

requirements for wind loading, and, while occupants in these areas are comparatively less likely to be 

injured or killed than occupants in other areas of the facility, best available refuge areas are not expected 

to offer life–safety protection against tornado hazards. Selection of in–facility best available refuge areas 

is recommended to be done in consultation with a qualified architect or engineer. Voluntary guidance for 

such selections is provided in FEMA P–431, Selecting Refuge Areas in Buildings (2009), and typically 

involves three steps: (1) determining the size of the refuge area (can vary by the age and any special needs 

of the occupants); (2) identifying the strongest portion(s) of the building by reviewing the design 

drawings and inspecting the facility (recommended to be performed by a qualified architect or engineer, 

primarily based on his or her experience and subjective judgment and not on any special detailed 

structural modeling due to the multitude of possible failure modes, the complex nature of tornadoes, and 

the variations in types of construction); and (3) assessing the refuge site to identify any potential 

nonstructural hazards (falling trees, power poles, etc.). 

At the time of the May 22, 2011, Joplin tornado, the City of Joplin did not have or operate any public 

shelters/safe rooms, nor did it require the construction of safe rooms in residential or commercial 

facilities. Interviews with a FEMA Region VII Hazard Mitigation Assistance Specialist107 indicated that 

there were three FEMA–funded public shelters/safe rooms in adjacent Newton County (south of Jasper 

County). These included a 1,388 ft2 shelter for 248 occupants in the Village of Stella; a 17,030 ft2 shelter 

for 2,500 occupants at Crowder College in Neosho; and a 14,039 ft2 shelter for 2,711 occupants at the 

Seneca R–7 School in Seneca. None of these public shelters/safe rooms were affected by the May 22, 

2011, Joplin tornado. 

Within the City of Joplin, based on information that NIST obtained through field damage surveys, 

subsequent NIST interviews, and data sharing with other organizations, NIST found that there were in– 

facility designated safe areas in several institutional and commercial high–occupancy buildings, as well as 

in–home shelters in residential buildings (in single homes, but not in apartment buildings) in the tornado– 

affected areas. High–occupancy facilities that had designated refuge areas and/or tornado emergency 

response procedures included commercial buildings (Walmart, Home Depot), schools (Joplin East Middle 

School, Joplin High School), and health care facilities (SJRMC, Greenbriar Nursing Home). In 

residential buildings, since most did not have a basement that could offer some protection in tornadoes 

(only about 16 percent of the residential buildings that sustained damage had either a crawl space or full 

basement, according to the Pictometry® database; the balance were of slab–on–grade construction), some 

residents had installed in–home concrete or steel tornado shelters. 

The effectiveness of a designated area of refuge is limited by the type of construction in which it is 

located, and current voluntary guidance for the selection of in–facility safe areas (FEMA P–431) relies 

upon the experience and subjective judgment of qualified architects or engineers (which can vary widely). 

Not surprisingly, then, the performance of designated safe areas during the May 22, 2011, Joplin tornado 

varied. Information on in–facility refuge areas in high–occupancy facilities and on selected in–home 

shelters is presented in the following sections in the form of case studies for use in evaluating the 

effectiveness of such refuges and associated sheltering practices. 

107 Laura Josephson, personal communication, May 25, 2011. 

204 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

3.3.1 Commercial High–Occupancy Facilities 

3.3.1.1 Designated Refuge Area at Walmart 

Through a review of design drawings and interviews with survivors, NIST was able to identify the 

designated refuge area in Walmart Store #59 (called the Site–to–Store or Layaway area of the store) 

where employees and shoppers were directed to shelter on May 22, 2011, as part of the store’s emergency 

plan (see Walmart evacuation details in Chapter 4). This designated refuge area (or best available refuge 

area) was in the back of the store, adjacent to the east perimeter CMU wall and near the only fire–exit 

door on that wall (see Fig. 3–119). Design drawings indicated that the design loads for the roof structure 

of the Layaway area included an additional 5.0 lb/ft2 downward pressure to account for the weight of 

hanging bicycles stored in the stockroom. The area was enclosed with 18– and 20–gauge steel stud (6 in. 

wide) interior partition walls with gypsum wall boards on both sides. There were wood shelving units 

along the interior partition walls, and a service counter as this area was used as a layaway and stockroom 

area. Thus, this area was near a hard perimeter wall (within the collapse radius of the east perimeter 

CMU wall) and the only fire exit at the back of the store. The design drawings indicated that this was not 

a hardened area and structurally there was little difference between this designated safe area and most 

other interior areas, except for the Tire and Battery Operation (TBO) area in the service bay outside the 

south perimeter CMU wall. NIST does not have information on how this area was selected as the 

designated refuge area for this facility (including whether a qualified architect or engineer was consulted 

or a structural evaluation was performed). 

Walmart’s Designated

Refuge Area 

TBO 

Area 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 3–119. Aerial photo showing the locations of the designated refuge area and TBO 

area in the Walmart store a drawing containing the refuge area. 

NIST NCSTAR 3, Joplin Tornado Investigation 205 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

As a result of the May 22, 2011, Joplin tornado, the roof system of the south half of the Walmart failed, 

with many steel roof trusses collapsing into the interior of the building, including into the designated 

refuge area. The east exterior CMU wall also collapsed inward onto the designated refuge area (see Sec. 

3.2.1.2). There were three fatalities and an unknown number of injuries at the store. It is not clear 

exactly where the three fatalities occurred; however, some of the injuries were confirmed through 

survivor interviews to have occurred in the designated refuge area. Accounts from survivors also 

indicated that the wood shelving units and counter in the refuge area might have acted as a dead stop that 

kept some of the roof trusses from collapsing completely to the floor, thus creating air space between the 

trusses and the floor and keeping some occupants of the refuge area from being more seriously injured. 

This fortuitous development, rather than protection designed into the refuge area, might have helped to 

reduce the number of casualties at the store. Overall, however, the designated safe area in Walmart Store 

#59 did not provide safe refuge for occupants in this particular tornado event. 

NIST’s review of structural drawings and its field damage survey also suggested that the TBO area, based 

solely on structural considerations, might have provided a better refuge than the designated area (see Fig. 

3–119). The TBO area, located behind the automobile service bay, was surrounded by hard CMU walls 

on all sides (the south perimeter CMU wall, which was laterally braced on both sides of the wall, and 

interior CMU partition walls on other sides). This area sustained envelope damage but did not sustain 

structural collapse. This observation highlights the need for structural evaluation in selecting best 

available refuge areas by a qualified architect or engineer. 

3.3.1.2 Designated Refuge Area at the Home Depot 

NIST was able to confirm the location of the Home Depot’s designated refuge area and review the store’s 

emergency response procedure (the procedure is described in Chapter 4) through interviews with 

representatives of the store. According to the information obtained by NIST, customers and store 

employees (associates) were directed, in accordance with the store’s emergency procedure, to the 

designated refuge area located in the Training Room in the back of the store. This Training 

Room/designated refuge area was located along the east perimeter wall, in the northeast section of the 

store near the loading dock (see Fig. 3–120). 

Design drawings indicated that the Training Room/designated refuge area was 34 ft  20 ft in plan, and 

bounded by the hard tilt–up east perimeter wall on the east side and three interior partition walls on the 

north, south, and west sides. The interior partition walls were made of steel stud frames (6 in. wide, 20– 

gauge, 16 in. on center), covered with 5/8 in. gypsum boards on one side and 1⁄2 in. plywood panels on the 

other. The hard wall that bounded the east side of this room comprised tilt–up wall panels that did not 

have positive connections to the concrete strip footing. North of this room was a group of wall panels 

(around the loading dock) that had some rotational capacity due to their positive wall–to–footing 

connection (designed for accidental truck collisions with the dock, see Fig. 3–46 in Sec. 3.2.1.3). The 

roof system was structurally similar throughout the store’s interior. Thus, structurally speaking, the area 

along the same (east perimeter) wall and about two wall panels north of the Training Room (adjacent to 

the locker room near the loading dock, see Fig. 3–121) might have been a better selection for the best 

available refuge area in this store. 

206 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

Area)

Chapter 3 

Interior Metal Stud Partition Walls Precast Tilt-up East Perimeter Wall 

Training Room 

(Designated Refuge) 

N

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

© 2013 Homer TLC, Inc. Used with permission. 

Figure 3–120. Location of the Training Room/designated refuge area at the Home Depot. Perimeter tilt–up wall panels here 

collapsed inward and onto the safe area. 

NIST NCSTAR 3, Joplin Tornado Investigation 207 
 

 

 

 

 

 

Chapter 3 

Training 

Room/designated 

refuge area 

Loading 

Dock 

Collapsed 

tilt-up 

panels of 

east 

perimeter 

wall 

Uncollapsed 

tilt-up panels 

in northeast 

corner 

Structurally 

more suitable 

area for 

refuge 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 3–121. North section of the Home Depot. Red line indicates perimeter tilt–up wall panels that collapsed.
 

Yellow line traces perimeter tilt–up wall panels (northeast corner, around loading dock) that did not collapse.
 

Red rectangle designates the Training Room/designated refuge area.
 

208 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

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Chapter 3 

As discussed in Sec. 3.2.1.3, the Home Depot sustained total collapse in the Joplin tornado, with 63 of its 

73 tilt–up perimeter hard wall panels collapsing either inward toward the interior of the building or 

outward away from the interior of the building. The perimeter hard wall panels that bounded the 

designated refuge area were among the 63 that collapsed. However, they fortuitously collapsed outward 

away from the building and the refuge area in the Training Room (see Fig. 3–121 and 3–122), and thus 

averting the potential for further injuries or fatalities among the building occupants who might have 

sought shelter in this area. 

In summary, the designated refuge area in the Home Depot did not provide better protection than other 

areas in the store during the May 22, 2011, Joplin tornado. An area near the loading dock may have been 

structurally more suitable to serve as a refuge, since the hard walls of this area had additional rotational 

capacity due to the design of the wall–to–footing connections. NIST does not have information on how 

the designated refuge area at this Home Depot was selected, including whether an experienced and 

qualified architect or engineer was consulted. Currently, such consultations are not mandatory and the 

selection can be done at the discretion of the facility owner. There were eight fatalities and an unknown 

number of injuries at the Home Depot. While media accounts indicated that there were injuries that 

occurred to occupants of the designated safe area, NIST was not able to obtain direct confirmation of the 

locations of the injuries and fatalities at this facility (see Chapter 4) including the designated refuge area. 

Collapsed tilt up 

wall panels along 

the east 

perimeter wall 

Training 

Room/designated 

refuge area 

Figure 3–122. View, from outside toward the west, of the Training Room/designated 

refuge area of the Home Depot. 

NIST NCSTAR 3, Joplin Tornado Investigation 209 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

3.3.2 Schools 

3.3.2.1 Designated Safe Areas at Joplin East Middle School 

Joplin East Middle School had six designated refuge areas identified by door signs stating “Tornado Safe 

Shelter.” The refuge areas served different sections of the school. The school emergency evacuation plan 

had pre–planned evacuation routes directing occupants to these shelters specifically for tornado 

evacuation. Fig. 3–123 shows the locations of these designated refuge areas and associated evacuation 

routes. 

As discussed in Sec. 3.2.1.4, Joplin East Middle School was the newest building complex among the 

engineered structures that were affected by the May 22, 2011, Joplin tornado, and two buildings toward 

the south half of the school, the Gymnasium and Auditorium, collapsed in the storm. NIST’s estimation 

of the wind environment using indirect methods (see Chapter 2) indicated that there was a sharp gradient 

between the wind speeds affecting the south and north halves of the school complex, with lower wind 

speeds affecting the north half (where most of the designated refuge areas were located). The collapsed 

structures were CMU and precast tilt–up BTS buildings with higher mean roof heights and longer span 

roof systems compared with other sections of the facility, which were made primarily of reinforced CMU 

walls with much shorter span roof systems (see facility description in Sec. 3.2.1.4). While the design 

drawings showed that the designated refuge areas were not specifically designed for tornado hazards, all 

six areas had design features known to typically survive tornadoes better than design features present in 

other areas of the school. These design features included being located toward the interior and away from 

windows, as well as having reinforced CMU hard wall protection and roof systems with short spans. The 

designated refuge areas were also located away from the Gymnasium and Auditorium, which were 

examples of a construction type that is known to have increased vulnerability to collapse in a tornado. 

NIST does not have direct information on how these designated refuge areas were selected as “tornado 

safe shelters,” or whether a qualified engineer or architect was engaged in the process. However, given 

the school’s structural system and layout, and the collapses of two major buildings in the complex that did 

not affect any of the designated refuge areas, it is reasonable to conclude that these designated refuge 

areas were appropriately selected and represented the best available refuge areas at the school. There was 

only minor roof envelope damage (roof coverings) in these areas as a result of the Joplin tornado. This is 

likely due to the combination of their tornado–resistant design features (reinforced CMU walls with short 

span roof system) and the less intense wind speeds to which they were exposed. Fortunately the school 

was not occupied at the time of the tornado and there were no reports of fatalities or injuries at the school 

as a result of the Joplin tornado. 

3.3.2.2 Designated Refuge Areas at Joplin High School 

Locations of “storm shelters” (blue shaded areas) and pre–planned evacuation routes (red arrows) on the 

first floor of Joplin High School are shown on Fig. 3–124. Although NIST was able to obtain only a 

partial set of drawings for this facility, information from the available drawings and field damage surveys 

indicated that these designated areas were the best available refuge areas, though not hardened areas or 

shelters designed in accordance with the tornado design criteria identified earlier in this chapter. The 

210 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

Chapter 3 

© 2007 Patterson Latimer 

Jones Brannon Denham 

(P.L.J.B.D.). Used with 

permission. Enhancements 

by NIST. 

Figure 3–123. Locations of Tornado Safe Shelters (color blocks) in Joplin East Middle School and their associated, pre–

planned tornado evacuation routes (arrows of corresponding color). 

NIST NCSTAR 3, Joplin Tornado Investigation 211 
 

 

 

 

 

 

 

Chapter 3 

RC frame building 

(see Figure 3–69) 

RC frame building 

(see Figure 3–70) 

Collapsed 

Gymnasium (see 

Fig. 3–72) 

Collapsed Auditorium 

(see Fig. 3–73) 

Collapsed wall (see 

Figures 3–74 and 

3–75) 

Source: FEMA MAT. Enhancement by NIST. 

Figure 3–124. Locations of “storm shelters” at Joplin High School and pre–planned emergency evacuation routes. 

212 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

”storm shelters” (blue shaded areas in Fig. 3124) at Joplin High School were located throughout the 

school complex, and thus would be easily accessible to the school’s occupants. All were located toward 

the interior of their respective buildings. The largest number of designated refuge areas was concentrated 

in the two RC frame buildings (see description of these buildings in Sec. 3.2.1.5) in the north end of the 

school complex (A and B hallways, rooms 101 to 103, 108, 109, 111, 119, 120). These refuge areas are 

located on the interior, unexposed sides of the building, thus utilizing both the stronger structural system 

(RC frame MWFRS) and protective elements (shielding by RC floors and walls). Other designated 

refuge areas toward the middle and south end of the school complex, where the MWFRS was mostly BTS 

with CMU walls and steel roof diaphragms, were in the interior, away from windows, and in building 

sections with short roof spans. 

While the high school sustained significant damage in the tornado (collapses of the BTS Gymnasium and 

Auditorium buildings at the south end of the school), and significant envelope damage on the wind– 

exposed sides of the RC frame buildings at the north end (see Fig. 3–66 and 3–67), none of the designated 

safe areas sustained any structural damage. The selection of these designated refuge areas appeared to 

have been well thought–out, and based on the aftermath of the May 22, 2011, Joplin tornado, these areas 

represented the best available refuge areas within the school complex. NIST does not have information 

regarding the selection process (whether qualified engineers or architects were engaged, etc.) or the 

school’s occupancy during the tornado. There were no reports of fatalities or injuries at this facility, and 

it was not known if anyone took shelter in any of the designated refuge areas during the storm. 

3.3.3 High–Occupancy Health Care Facilities 

NIST was able to obtain partial design information for the Ozark Center, including information on the 

locations of its designated refuge areas. NIST obtained information regarding emergency protocols used 

at SJRMC through interviews with survivors, and at the Greenbriar Nursing Home through interviews 

with survivors conducted by the CDC EPI–Aid study (see Chapter 4). This information, combined with 

data obtained from NIST’s field damage surveys, is reflected in the following discussion of the 

availability and effectiveness of refuge areas, if any, in these facilities. 

3.3.3.1 Designated Refuge Areas at Ozark Center for Autism 

As discussed in Sec. 3.2.2.1, the RC frame Ozark Center for Autism building sustained significant 

damage to its envelope and interior, but no structural damage to its MWFRS. Design drawings showed 

that the building had two designated “areas of refuge” located in the two stairwells of the building (see 

Fig. 3–125). These two areas were protected on all sides by reinforced CMU wall enclosures. Damage 

survey observations found that, while the building interior sustained significant damage as a result of 

wind and debris infiltration after the failure of the building envelope, the reinforced CMU stairwell 

enclosures were not damaged and thus would have continued providing protection for any refuge 

occupants. 

NIST does not have information regarding occupancy of this building at the time of the May 22, 2011, 

Joplin tornado, including whether any occupants took shelter in the designated areas of refuge. Given the 

building design features and interior layout, as well as the significant damage that occurred to the building 

interior due to wind and debris infiltration (which highlighted the vulnerability of all interior areas of this 

NIST NCSTAR 3, Joplin Tornado Investigation 213 
 

 

 

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© 2007 Elliott Hunter AIA. Used with permission. Enhancements by NIST. 

Figure 3–125. Locations of areas of refuge (AOR, red blocks) on the first floor of the Ozark Center building. 

214 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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building to tornado hazards despite the building’s strong MWFRS), the two designated “areas of refuge” 

appeared to have been appropriately selected. With the protection afforded by the reinforced CMU wall 

enclosures and their easy accessibility for building occupants, these areas represented the best available 

refuge areas compared with all other areas of this building. 

3.3.3.2 Designated Refuge Areas at SJRMC 

In case of emergency, the Condition Gray (see discussion in Chapter 4) emergency protocol in the East 

and West Towers of SJRMC, when executed, called for patients on each floor of the towers to be moved 

from their rooms (along the perimeter of each floor) into the hallway at the center of the floor. Thus, the 

hallway on each floor in SJRMC’s East and West Towers was in effect used as a designated refuge area 

in the May 22, 2011, Joplin tornado. The use of these hallways, instead of more central, protective 

locations, was necessitated by the typically short tornado warning time and the complexity involved in 

quickly evacuating patients from multiple floors to such central locations. 

As discussed in Sec. 3.2.1.1, the East and West Towers sustained minimal damage to their structural 

systems, but severe damage to their vertical envelopes (almost all dual–pane insulated glass windows 

were broken) and interior areas, including the hallways (designated refuge areas), due to wind pressure 

and wind–borne debris (see Fig. 3–126). According to interviews with survivors (see Sec. 4.4.8), 

occupants of the hallways were impacted by all sorts of wind–borne debris (medical equipment, x–rays, 

chairs, broken doors and glass, hailstones, insulation, etc.). Thus, while the hallways may be considered 

the best available refuge areas relative to other areas of each floor (except for the small areas in the three 

stairwells on each floor, which might be too small for the number of patients per floor and for more 

seriously ill patients) as they were furthest away from the windows of the patient rooms (see Fig. 3–127), 

they also were severely affected by the tornado hazards and did not provide adequate protection to 

occupants against wind and debris infiltration. The 14 fatalities that occurred at SJRMC included four 

ICU patients who were on respirators and believed not to have been moved into the hallways, one person 

located on the 3rd floor, and nine other occupants who were injured and subsequently died as a result of 

their injuries. Given the hazardous conditions caused by wind–borne debris described by occupants of the 

hallways (see Sec. 4.4.8), it is not unreasonable to conclude that there were injuries that occurred to 

occupants of the hallways/designated refuge areas in the SJRMC towers. However, NIST was not able to 

confirm the locations of the nine occupants who were injured and subsequently perished due to their 

injuries. 

The damage at SJRMC ultimately led to the total demolition of the hospital and the construction of a new 

Mercy Hospital in Joplin at I–44 and Main Street, about 3 miles south of the old hospital site. According 

to the Sisters of Mercy,108 the new facility, scheduled for completion in early 2015, will feature two 

underground levels and eight levels above ground. The lower floors will serve as shelter in place areas 

for the hospital. The above–ground floors will have safe zones with heavy–duty steel doors and other 

storm–resistant features such as laminated glass throughout the facility, hurricane–rated windows in 

critical areas, a concrete and brick exterior, two independent electrical feeds, two generators housed in a 

storm–resistant building (either generator can power the hospital independently) and windowless 

stairwells equipped with emergency lighting. 

108 www.mercy.net/sites/default/files/files/mercy-joplin-tornado-and-recovery-quick-facts-6324.pdf. 

NIST NCSTAR 3, Joplin Tornado Investigation 215 
 

 

 

 

 

 

 

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© 2011 Curtis Lynn Geise. Used with permission. 

Figure 3–126. View of a typical hallway with damaged interior (ceiling, walls, and debris); 

hallways were used as designated refuge areas in SJRMC’s East and West Towers.

© 2011 Curtis Lynn Geise. Used with permission. 

Figure 3–127. Typical floor plan of SJRMC’s East and West Towers (patient rooms along 

perimeter and hallway toward the center). 

216 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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3.3.3.3 Designated Refuge Areas at the Greenbriar Nursing Home 

NIST conducted a field damage survey of this facility after the May 22, 2011, Joplin tornado but was 

unable to obtain any design information or information regarding any areas within the building that were 

formally designated as refuge areas. The survey found that this unreinforced CMU building with a wood 

truss roof collapsed completely and there were no areas in its interior that were structurally hardened or 

protected with strong interior building elements and thus more suitable than other areas for use as refuges. 

Emergency procedures for tornadoes at this facility, described in Sec. 3.4.2, called for the staff to move 

residents to inner hallways and close all doors to residents’ rooms to avoid flying glass. On May 22, 

2011, the staff reportedly placed as many residents as possible in the central hallway (the hallway of the 

core section). Thus, according to these accounts, the central hallway of the core section, while there was 

no information confirming that it was formally designated as the refuge area, in effect was used as the 

designated refuge area (best available) at the Greenbriar Nursing Home on May 22, 2011. 

This area, as all areas of this facility, sustained total collapse and people located there were exposed to 

impact by fallen construction materials as well as wind–borne debris. The total failure of this area 

illustrates that the effectiveness of the best available refuge area in a facility is constrained by the overall 

capacity of the host building. In buildings with structural systems that are more susceptible to collapse in 

tornadoes, the best available refuge area may not offer any real or increased protection. Occupants of 

older, high–occupancy facilities with residential types of construction (unreinforced CMU walls with 

wood roof systems) like the Greenbriar Nursing Home, were vulnerable during the May 22, 2011, Joplin 

tornado due to the lack of protection afforded by their in–facility refuge areas and the lack of access to 

any public shelters. As reported in Chapter 4, the Greenbriar Nursing Home sustained the highest number 

of fatalities, 19, for a single facility during the May 22, 2011, Joplin tornado. 

3.3.4 In–Home Shelters 

Like many other municipalities in tornado–prone areas, the City of Joplin does not mandate the 

construction of storm shelters or safe rooms in residential buildings (single–family homes or apartment 

buildings) or businesses. And at the time of the May 22, 2011, Joplin tornado, neither the City of Joplin 

nor Jasper County had or operated any public shelters or safe rooms. 

While the potential life–saving benefits of in–home storm shelters/safe rooms in tornadoes are clear, and 

are demonstrated by the examples discussed later in this section, mandating them for residential 

construction, especially for multi–family apartments, would require careful consideration of other 

complex issues beyond the additional cost, including operational, accessibility, and liability issues. These 

complex legal and operational issues often militate against mandating the installation of storm 

shelters/safe rooms. As a result, municipalities in tornado–prone areas, despite knowing the risks and 

benefits, typically choose to encourage, rather than require, residential property owners to install storm 

shelters. 

As indicated in Sec. 3.1, data from the Missouri Housing Development Commission showed that many of 

the areas affected by the May 22, 2011, Joplin tornado had high concentrations of rental properties, and 

thus a significant portion of the 20,820 people living in the affected area were likely renters (about 4,600 

NIST NCSTAR 3, Joplin Tornado Investigation 217 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

rental units were destroyed according to the Joplin Globe109). With the lack of public shelters in Joplin 

and with apartment buildings not required to provide shelters, this portion of the affected population 

would, in general, be expected to be more vulnerable to tornadoes as they depend for their protection on 

properties built and controlled by others. Often, the only options for shelter in multi–family buildings are 

the internal hallways of lower floors or the internal spaces, such as bathrooms or closets, within individual 

apartments. 

In single–family homes, sheltering options beyond internal hallways, bathrooms, and closets may exist if 

an underground space (crawl space or basement) is available. The National Weather Service’s pre– 

tornado warnings state that for people indoors “the safest place to be during a tornado is in a basement...” 

(see Sec. 4.6.2.2). In Joplin, due to geologic conditions, it is uncommon for residential structures to 

include basements (of the single–family homes that were affected in Joplin, only about 17 percent had 

either a full or partial basement according to the Pictometry® database). For residences in Joplin without 

space underground, one option has been to install an in–home storm shelter. 

The design of in–home shelters (storm shelters and safe rooms) varies and encompasses both portable 

(pre–manufactured in factory and installed at job site) and custom–built (constructed at job site) shelters. 

Portable shelters are constructed in factory settings and are typically installed above–grade at the 

residence. Custom–built shelters are custom–built either as part of the design of new homes or as 

additions to existing homes and, if conditions allow, are likely to be located below ground (in a 

basement). The storm shelter industry is not regulated by the states or Federal Government and there are 

no mandated design criteria for in–home shelters in current building codes. Manufacturers and builders 

may follow voluntary guidelines provided by FEMA or ICC 500 in designing and constructing their 

shelters. 

Two types of portable, in–home shelters were found in Joplin: steel shelters and Kevlar® –reinforced 

shelters. Published information provided by manufacturers of these shelters indicated that they were 

designed based on criteria recommended in FEMA–320 and proof–tested against laboratory–simulated 

tornado hazards (wind speeds up to 250 mph and wind–borne debris impacts using 15 lb, 2  4 projectiles 

launched at 100 mph). Portable shelters are typically installed above–grade on concrete floors, often in 

garages, using anchor bolts (conventional steel bolts as well as epoxy anchors). The cost of installing a 

shelter of this type can vary with the size of the shelter (reportedly from around $5,000 to $15,000). For 

custom–built shelters, the primary construction material is typically reinforced concrete, and prescriptive 

guidance for the design and construction of custom–built shelters is also provided in FEMA publications. 

However, laboratory proof testing cannot be performed for custom–built shelters since they are not 

portable. Also, because there are no regulations governing the storm shelter industry, the design and 

construction of custom–built, in–home shelters can vary along with the qualifications and experience of 

their builders. 

As in–home shelters were not mandated at the time of the May 22, 2011, Joplin tornado, there were no 

data on how many of the 7,411 damaged residential structures had in–home shelters. A factsheet110 

issued by the manufacturer of Twister SafeTM steel shelters indicated that there were 8 homes with 

Twister Safe storm shelters in the affected areas in Joplin on May 22, 2011. Several instances of in–home 

109 “Tornado poses questions about putting shelters in apartment buildings,” Wally Kennedy, The Joplin Globe, Joplin, MO, August 

6, 2011. 

110 www.mssu.edu/news/2012/january/Twister-Safe-2012.php. 

218 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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shelters providing protection to residents have been reported since the tornado. In this section, two such 

instances, involving above–ground steel and Kevlar® –reinforced shelters, are described. These shelters 

were in homes located west of SJRMC with different proximities to the center of the tornado damage path 

and different degrees of damage. 

3.3.4.1 In–Home Steel Shelter 

An above–ground portable steel shelter was installed in a home on South Adele Avenue, in close 

proximity to the estimated center of the tornado damage path and directly west of SJRMC. The wood– 

frame home and surrounding similarly constructed homes in this area sustained complete demolition (see 

Fig. 3–128). The home belonged to a family who had experienced a tornado and lost one family member 

as a result 3 years before in Racine, Missouri. This experience factored into the family’s decision to 

install the portable steel shelter, which reportedly cost $4,000, in the new family home on South Adele 

Avenue. As shown in Fig. 3–128, the wood–frame home was completely destroyed during the May 22, 

2011, Joplin tornado, but the steel shelter was not damaged and remained anchored to the concrete garage 

floor. The homeowner and his daughter, who took shelter in this storm room, emerged unscathed. 

3.3.4.2 In–Home Kevlar® –Reinforced Shelter 

An above–ground Kevlar® –reinforced shelter was installed at a wood–frame home located on Alabama 

Avenue, west of SJRMC and in an area that sustained significant damage (see Fig. 3–129). The 4 ft  4 ft 

shelter had Kevlar® lining for its roof and walls, and was anchored onto the concrete garage floor using 

epoxy anchors. The home sustained significant damage, with the roof disconnected and lost and other 

damage to windows and the interior due to wind and debris infiltration. The shelter appeared completely 

intact, however, and the owner who took refuge in the shelter was unscathed (see Fig. 3–129 and 3–130). 

3.3.5 Summary of Performance of Shelters/Designated Refuge Areas 

The following are findings that pertain to the performance of shelters/designated safe areas during the 

May 22, 2011, Joplin tornado: 

	 The City of Joplin, like most other municipalities in tornado high hazard areas, and consistent 

with the adopted model building codes then in effect, did not mandate the construction of storm 

shelters/safe rooms in residential or commercial facilities at the time of the May 22, 2011, Joplin 

tornado. 

	 The lack of community storm shelters and of safe rooms in multi–family residential or 

commercial facilities meant that a large portion of Joplin population in the affected area who 

were living in multi–family residential buildings, or who were residents of nursing homes, did not 

have a protective option during the May 22, 2011, Joplin tornado. 

	 Individuals in Joplin had very few options for underground or tornado–resistant shelters. There 

were no community shelters or safe rooms in the City of Joplin or Jasper County at the time of 

the May 22, 2011, Joplin tornado. Also, 82 % of the homes in Joplin, MO were built without 

NIST NCSTAR 3, Joplin Tornado Investigation 219 
 

 

 

 

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© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 3–128. Wood–frame home completely destroyed except for the steel shelter bolted to the concrete floor in the 

garage. 

220 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

Chapter 3 

Figure 3–129. Above-ground 

Kevlar® storm shelter bolted to 

concrete garage floor in 

residence that was damaged 

during the tornado. 

Source: FEMA MAT. 

Source: FEMA MAT. 

Figure 3–130. Extent of damage (roof system disconnected) at residence with in–home, 

above–ground Kevlar® storm shelter. 

NIST NCSTAR 3, Joplin Tornado Investigation 221 
 

 

 

 

 

 

 

 

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basements. Only a few non–residential buildings were equipped with underground locations (e.g., 

basements), and none identified with tornado–resistant above–ground shelters. 

	 While many of the facilities had designated refuge areas, several of these areas suffered severe 

damage. NIST found no evidence that these areas yielded positive outcomes with respect to loss 

of life. Most high–occupancy commercial and critical facilities surveyed by NIST in the tornado 

affected area (hospital, schools, and big–box stores) had in–facility designated refuge areas for 

tornados. However, the designation of these areas for refuge was not based solely on structural 

considerations. There are currently no design standards, requirements or best practice guidelines 

for designating refuge areas within existing commercial and critical buildings. 

	 Currently, there are optional model code provisions for design of specially purposed storm 

shelters and safe rooms, but such shelters are not required. 

	 Based on a few instances observed in this tornado, in–home shelters did perform well and 

provided life safety protection to the home owners. NIST found no data on how many of the 

approximately 7,411 damaged residential structures had in–home tornado shelters. 

3.4	 PERFORMANCE OF LIFELINES AS RELATED TO BUILDING 

FUNCTIONALITY 

3.4.1	 Overall Tornado Effect on Lifelines in Joplin 

The tornado caused significant damage to electrical power, water, and gas utilities. The damage and 

service disruptions sustained by each of these lifelines are described in this section, using information 

111,112,113 from documents and interviews provided by the utility companies, from the Missouri Public 

114	 115,116 Service Commission, and from the City of Joplin.

3.4.1.1	 Electricity 

The May 22, 2011, Joplin tornado’s effects on the electrical power system and infrastructure in the Joplin 

area caused approximately 20,000 Empire District Electric (EDE) customers to lose power during or 

immediately after the storm. Below is a summary of the overall damage to the local electrical power 

infrastructure: 

	 Transmission System 

	 10 high–voltage transmission lines out of service. 

111 https://www.empiredistrict.com/newsroom/default.aspx. 112 Missouri American Water Joplin Tornado Response (http://tristatewater.org/wp-content/uploads/2011/11/Matt-Barnhardt-MoAmerican-Joplin-Tornado-Response.pdf). 113 https://www.missourigasenergy.com/MGE/companyInfo/news.jsp. 114 The Joplin Experience: Utility and Regulator Lessons from the Past, Present, and the Future (http://psc.mo.gov/CMSInternetData/ 

PSConnection/Publications/PSConnection%2011-11.pdf). 115 www.joplintornadoanniversary.com/resources/city-of-joplin-factsheet5-14-12.pdf. 116 www.joplintornadoanniversary.com/resources/community-press-kit.pdf. 

222 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

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	 135 transmission towers affected. 

	 Substations 

	 Six power substations with step–down transformers initially impacted. Two of these 

(Substations 422 and 430) were damaged but repairable. One was completely destroyed 

(Substation 59, open steel frame, in close proximity to the estimated center of the tornado 

damage path, see Fig. 3–131). 

	 Several transformers at the damaged substations sustained damage and leaked. 

	 Distribution System 

	 Approximately 110 miles of aerial distribution line downed. 

	 Approximately 4,000 distribution poles damaged. 

	 31 of 60 circuits damaged. 

	 Fiber 

	 30 fiber lines cut. 

Following the tornado, and on an initial assessment of the damage, EDE focused first on de–energizing 

the downed power lines to ensure the safety of the public and emergency responders. Restoration of 

power was prioritized for critical facilities, i.e., hospital, other health care, human services, water, and 

communications facilities. Main feeders were restored to the Freeman Health System hospital (one of the 

two hospitals in Joplin, the other being SJRMC) well before dawn on the morning of May 23, 2011. 

Power was also restored to the Missouri American Water intake facilities before dawn on May 23, 2011 

to the water treatment plant within 24 hours after the tornado, and to well facilities within 72 hours after 

the tornado. Power was provided to the temporary St. John’s Mercy Hospital location when it opened 

within 1 week of the storm. Schools were not included in the initial prioritization because the school year 

was already finished and schools were not being used as shelters. 

EDE requested assistance from the Midwest Mutual Assistance Group on the afternoon of May 23, 2011. 

Whatever manpower, materials, and equipment were needed for restoration of power to critical facilities 

were given top priority, and remaining resources were used to begin work on other parts of the system. 

Repairs of transmission lines and work to repair or bypass the damaged substations were conducted 

simultaneously. The main thoroughfare in Joplin (along Range Line Road) was restored within 3 days. 

EDE worked to meet requests to restore power to businesses, while also reconnecting neighborhoods. 

Customers on the outer edges of the impacted area were switched to undamaged circuits that required no 

rewiring. In areas where there was some damage but the system was salvageable, repairs were made, and 

in areas where the system was heavily damaged or destroyed, it was rebuilt, typically from the outer 

edges in. Within the damaged area, electricity was not restored to buildings until after they were “green 

tagged” (i.e., determined to be safe for occupancy) by the city. In the most heavily damaged and 

destroyed areas, the system was completely redesigned and rebuilt, following a 2–month rebuilding 

moratorium issued by the city. 

NIST NCSTAR 3, Joplin Tornado Investigation 223 
 

 

 

 

 

 

 

 

 

 

 

 

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Heavily damaged residential neighborhoods having underground power distribution systems (e.g., west of 

Schifferdecker Avenue between 20th and 32nd Streets) took longer to restore than those with overhead 

systems. The underground service entrance pedestals were commonly damaged and buried under debris. 

EDE had to first verify that the power was out at each pedestal, then clear the debris and make repairs. 

There was often damage to the underground lines between the pedestal and the house, which was not 

always obvious. It was the responsibility of the home owner to have this damage repaired, which further 

delayed the power restoration. 

A timeline for the restoration of power is provided in Table 3–7. Among the 20,000 customers who 

initially lost power, all customers able to receive power had it restored within 10 days to 12 days. Of the 

approximately 8,000 customers not initially able to return to the system, EDE reported that as of March 

2013, 6,600 had returned. As of June 30, 2011, the total cost to rebuild the system, including substations, 

was estimated at $25.7 million. By the one–year anniversary of the May 22, 2011 Joplin tornado (May 

22, 2012), about 95 percent of the damaged primary power lines had been rebuilt. And on October 17, 

2012, about 17 months after the May 22, 2011, Joplin tornado, the reconstruction of the destroyed 

Substation 59 was completed with its return to service. 

3.4.1.2 Water 

The tornado caused significant damage to the water system, which is described below using information 

from Missouri American Water Company (MAW) and the Missouri Public Service Commission:117 

	 There were about 4,000 leaks in residential service lines and 25 torn fire–service lines. Even 

though MAW’s transmission and distribution systems were underground, the multitude of 

above–ground leaks in service lines, primarily the result of uprooted trees and damage to 

homes and businesses (broken pipes), caused the pressure throughout the system to drop to 

well below the normal standard operating level and triggered the issuance of a water boil 

order by MAW and the Missouri Department of Natural Resources. The drop in water 

pressure and the damage to the fire–service lines could have reduced firefighting 

effectiveness in some areas of Joplin had it been needed. 

	 Two elevated water storage tanks lost pressure within 10 minutes, and were empty less than 2 

hours after the May 22, 2011, Joplin tornado struck. 

	 An unreinforced brick storage building (built in 1898) that was part of MAW’s water 

treatment plant collapsed. The plant was otherwise undamaged and remained operational on 

backup power. 

Following the tornado, MAW first worked to shut down the entire system serving the affected area to stop 

the water pressure from continuing to drop. The company then conducted block by block walk–throughs 

of the impacted areas to shut down the 4,000 leaking service lines and 25 torn fire–service lines, while 

opening water mains to ensure that the impacted zone had fire protection. 

117 https://www.empiredistrict.com/newsroom/default.aspx. 

224 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

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Table 3–7. Timeline of electrical power restoration. 

Date Time 

Reported Estimates of 

Number of customers 

without power Comments 

May 22 late afternoon 20,000 estimated total customers lost power 

May 23 11am 18,000 

May 23 4pm 14,000 

May 23 9pm 13,700 

May 24 11am 17,000 Additional numbers due to additional customers reporting loss of service 

May 24 4pm 16,000 FEMA estimated that 10,000 within storm path damaged area 

May 24 9pm 14,000 

May 25 5pm unavailable EDE's Outage Management System (OMS) suffered a direct lightning strike earlier in the day 

May 25 9pm 11,500 

May 26 5pm 11,000 

May 27 5pm 9,500 

May 28 5pm 8,000 

May 29 5pm NR EDE believed a significant number of the customers who are currently without service and can receive it 

will have electricity restored by tomorrow evening. 

May 30 5pm NR EDE and visiting crews made continued progress today restoring service to several hundred facilities. Most 

large groups of customers have been returned to service and work to pick up small groups and individual 

customers is continuing. 

May 31 5pm NR EDE reported it believes service has been restored to nearly all customers who are able to receive service. 

However, in light of the massive restoration effort, it is possible that a few customers may have been 

missed. 

Key: NR, not reported.
 

Source: Empire District Electric press releases (https://www.empiredistrict.com/newsroom/default.aspx) and interview with EDE Director of Engineering and Line Services.
 

NIST NCSTAR 3, Joplin Tornado Investigation 225 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Within 24 hours after the May 22, 2011, Joplin tornado, water pressures had recovered in 60 percent of 

the Joplin system, although there was still a water boil order in place. Within 48 hours, pressures had 

returned to normal across the system except in the impacted area, and system flushing was begun. In the 

impacted area, all of the major leaks had been stopped within 4 days of the tornado, and fire service was 

then fully restored. The water boil order was lifted within 51⁄2 days. 

3.4.1.3 Natural Gas 

The Missouri Public Service Commission118 reported the following damage to Missouri Gas Energy’s 

(MGE) infrastructure, which NIST confirmed in an interview with MGE: 

 Approximately 3,500 gas meters were damaged or destroyed, and a multitude of gas leaks 

were caused by service–line pipes that were broken, when structures were destroyed. 

 Roughly 55,000 ft of gas mains sustained damage. 

Despite significant damage, service generally remained uninterrupted in undamaged areas. In responding 

to the emergency, MGE was able to shut off entire sections of the gas distribution system in some areas— 

shutting off individual gas leaks from damaged residences in the process. However, in areas with gas 

mains that also served critical facilities (like Freeman Health System hospital in Joplin) and needed to 

remain operational, MGE could not shut off the gas mains. Instead, it had to conduct street–by–street 

walking surveys of individual damaged structures ahead of the demolition and debris removal teams to 

shut off those service lines and risers serving structures that were damaged to the point of being 

uninhabitable. It took approximately 2 weeks for MGE to completely shut off all gas leaks. As of May 

22, 2012, a year after the May 22, 2011, Joplin tornado, MGE had replaced roughly 70 percent of the 

damaged mains and restored approximately 20 percent of its service to those affected by the storm. 

3.4.1.4 Communications 

EDE reported that a total of 21 cell towers were nonfunctional following the May 22, 2011, Joplin 

tornado. The wireline network also experienced damage to aerial fiber–optic and copper cables. Voice 

communications in particular were severely degraded, although text messages were often able to get 

through. Mobile cellular towers were deployed by wireless carriers beginning less than 24 hours after the 

May 22, 2011, Joplin tornado. AT&T reported placing and splicing 18,000 ft of fiber and copper cables 

by May 27, 2011.119 Communications remained problematic for several days following the May 22, 

2011, Joplin tornado. 

118 The Joplin Experience: Utility and Regulator Lessons from the Past, Present, and the Future (http://psc.mo.gov/CMSInternetData/ 

PSConnection/Publications/PSConnection%2011-11.pdf). 119 https://www.empiredistrict.com/newsroom/default.aspx. 

226 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

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© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 3–131. Destroyed EDE Power Substation 59. 

NIST NCSTAR 3, Joplin Tornado Investigation 227 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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3.4.2 Effect of Lifeline Disruptions on Building Operations 

To examine the effect that the tornado–induced lifeline disruptions had on the ability of buildings to 

remain operational, it is instructive to compare the performance of the two hospitals in the region, SJRMC 

and Freeman Health System hospital in Joplin. Both facilities were affected, but to different degrees, by 

the May 22, 2011, Joplin tornado. SJRMC’s buildings sustained significant damage to their envelopes 

and interiors (affecting windows, window mullions, roofs and roof coverings, curtain walls, partitions, 

ceilings, electrical fixtures and wiring, HVAC ductwork and equipment, and general building contents), 

with the generator building completely collapsed and the emergency power generator and power 

distribution system subsequently destroyed (see Sec. 3.2.1.1). Freeman Health System hospital in Joplin 

was outside of the damaged area and was only temporarily affected by the region–wide disruption of 

lifeline services, but otherwise was not impacted by the May 22, 2011, Joplin tornado. The extent of 

lifeline disruptions experienced at both facilities is summarized below: 

	 SJRMC: 

	 Loss of main power supply due to overall damage to electrical transmission and 

distribution systems (downed feeder lines from Substation 59, damaged distribution poles 

and transmission towers, and the collapse of Substation 59 itself). 

	 Loss of emergency backup power due to the collapse of the generator building and 

associated damage to, and complete loss of, the emergency power generator and power 

distribution system. 

	 Damaged interior electrical distribution system due to failure of buildings’ envelopes and 

subsequent wind and debris infiltration. 

	 High–pressure natural gas leak due to damage to the reducer gas pipe on the west wall of 

the Chiller Plant building (see Fig. 3–132). 

	 Damaged and leaking liquid oxygen tank on the west side of SJRMC (see Fig. 3–133). 

	 Damaged water and gas service lines. 

	 Damaged interior water and sprinkler systems. 

	 Freeman Health System hospital in Joplin: 

	 Loss of main power supply due to downed main and backup feeder lines to the facility. 

The facility continued to operate using backup power until the main power supply was 

restored. As the hospital was not structurally affected, all lifeline distribution systems 

within the facility remained intact and functional. 

In terms of continuity of operations, the difference between SJRMC and Freeman Health System could 

not be more drastic. SJRMC immediately set up a triage area and, within a week, a 60–bed temporary 

field hospital in the parking lot of the existing hospital complex, but was never able to return its damaged 

facilities to any levels of operation, and ultimately decided to abandon the damaged facility and rebuild at 

228 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

Chapter 3 

Figure 3–132. High–pressure gas reducer valve at SJRMC that was damaged 

and leaked. 

Figure 3–133. Liquid oxygen tank at SJRMC that leaked. 

NIST NCSTAR 3, Joplin Tornado Investigation 229 
 

 

 

 

 

 

 

 

 

 

 

 

Chapter 3 

another location. In contrast, by May 23, 2011, a day after the tornado, Freeman Health System in Joplin 

was connected to an alternate electrical feeder line and full power supply and the hospital’s full 

functionality was restored. The complete loss of building functionality at SJRMC meant that Freeman 

Health System and other regional hospitals had to accommodate a sudden increase in the demand for their 

services from people affected by the tornado. Operating on its backup power supply, Freeman was able 

to provide care for more than 500 wounded survivors in the first hours after the storm, including 22 life– 

saving surgeries in the first 12 hours, and eventually, with its main power supply restored, served more 

than 1,700 victims of the May 22, 2011, Joplin tornado in the days that followed the event. 

The different outcomes between the two hospitals illustrated that, despite the damage sustained by lifeline 

systems and the complexity involved in restoring services due to debris– and safety–related issues, 

regional utilities were able to cope and provide services to those critical facilities that were still able to 

receive them. In other words, the disruption of lifeline services available to SJRMC was not the main 

reason for the facility’s loss of functionality. Rather, it was the devastation to its buildings’ interiors 

caused by the failure of building envelopes that was the primary reason for the complete loss of 

functionality. Even if SJRMC’s emergency backup power supply had not been disrupted, the facility 

would still not have been able to receive restored lifeline services (as did Freeman Health System hospital 

within 1 day) due to the widespread interior damage that destroyed SJRMC’s internal lifeline distribution 

systems. Thus, while backup power is important for enabling the uninterrupted operation of critical 

facilities, as was demonstrated by Freeman Health System hospital, better protection of building 

envelopes is also important for enabling backup and restored lifeline services to be utilized, as well as for 

better protecting building occupants. 

In terms of structural capacity, critical facilities with a robust MWFRS and lateral load system that does 

not rely on the roof diaphragm for stability, like concrete and steel moment frames, demonstrated their 

ability to resist intense tornado hazards (wind speeds well in excess of the design wind speed, plus 

impacts by all manner of wind–borne debris) without structural collapse in the May 22, 2011, Joplin 

tornado. However, with regard to the lifeline services required for continued operation of such facilities, 

the May 22, 2011, Joplin tornado highlighted that these services comprise two separate segments. One 

segment is external to the facilities, controlled by lifeline service providers, and consists of regional 

transmission and distribution systems. Regional utilities demonstrated in the Joplin tornado that lifeline 

services can be quickly and safely restored to critical facilities (including health care providers, fire 

stations, and water supply and treatment facilities) despite the severity of the damage and the complexity 

of restoration. 

The other segment of lifeline services is internal to the facilities, and consists of the backup and 

distribution systems controlled by the facilities. It is this second segment of lifeline systems that, if not 

well protected, can cause prolonged disruptions to facility operations by rendering the facility unable to 

receive restored services from utility providers. This segment, to remain functional, requires that building 

envelopes remain intact. Protected envelopes are also needed to maintain vertical movement (elevators) 

in multistory buildings. Thus, the most important issue that must be addressed to maintain the 

functionality of critical facilities in tornadoes may be requirements for improved performance/protection 

of building envelopes. Losing the envelope also means that, even if utilities are restored after a tornado, 

the building would remain non–functional due to the inability to meet operational requirements of the 

building codes for maintaining temperature control. Improved performance of the building envelope, in 

the case of SJRMC, would have required impact–resistant window glazing and more robust curtain walls 

230 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

Chapter 3 

like those rated for hurricane–prone regions. While this would add cost to the construction of critical 

facilities, this added cost must be weighed against the potential costs associated with the disruption of 

services that are vital to a community, as well as the costs associated with proper clean up, demolition, 

and rebuilding. 

3.4.3 Summary of Performance of Lifelines 

The followings findings are related to performance of lifelines that pertain to the operation of buildings 

during the May 22, 2011, Joplin tornado: 

	 All utilities (water, gas, power) were lost in the areas damaged by the May 22, 2011, Joplin 

tornado. While the utilities restored service to critical buildings (e.g., hospitals, water treatment 

plant) within 24 hours, the damage sustained within these buildings did not allow them to utilize 

the power, water and gas service. 

	 Despite the devastation sustained by lifeline systems and the complexity involved in restoring 

services due to debris– and safety–related issues, regional utilities were able to cope and restore 

services to those critical facilities that were still able to receive them. 

	 Failure of the building envelope of the NIST–surveyed critical facilities, leading to damage to 

internal lifeline distribution systems, was the primary cause of their complete loss of building 

functionality. Losing the envelope also meant that, even if utilities had been restored after the 

May 22, 2011, Joplin tornado, the building remained non–functional, due to the inability to meet 

building code requirements for maintaining temperature control. 

	 The design wind speed for critical buildings built prior to 1998 was higher than that used for 

buildings that housed the backup generators for those critical buildings. 

NIST NCSTAR 3, Joplin Tornado Investigation 231 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.5 

Chapter 3 

REFERENCES 

ACI (American Concrete Institute). 1996. Building Code Requirements for Masonry Structures. ACI 

530/ASCE 5/TMS 402. November. 

ACI (American Concrete Institute) Committee 551. 1997. Tilt–Up Concrete Structures. Reported by 

ACI Committee 551. ACI 551 R–92. Reapproved 1997. American Concrete Institute. Farmington 

Hills, MI. 

ACI (American Concrete Institute) Committee 551. 2003. Tilt–Up Concrete Structures. Reported by 

ACI Committee 551. ACI 551 R–92. Reapproved 2003. American Concrete Institute. Farmington 

Hills, MI. 

ANSI/ANS (American National Standards Institute/American Nuclear Society). 1983. Standard for 

Estimating Tornado and Extreme Wind Characteristics at Nuclear Power Sites. ANSI/ANS–2.3– 

1983. American Nuclear Society. La Grange Park, IL. 

ANSI/ANS (American National Standards Institute/American Nuclear Society). 2011. Estimating 

Tornado, Hurricane, and Extreme Straight Line Wind Characteristics at Nuclear Facility Sites. 

ANSI/ANS–2.3–2011. American Nuclear Society. La Grange Park, IL. 

ASCE (American Society of Civil Engineers). 1995. Minimum Design Loads for Buildings and Other 

Structures. ASCE 7–95. New York, NY. 

ASCE (American Society of Civil Engineers). 1998. Minimum Design Loads for Buildings and Other 

Structures. ASCE 7–98. New York, NY. 

ASCE/SEI (American Society of Civil Engineers/Structural Engineering Institute). 2010. Minimum 

Design Loads for Buildings and Other Structures. ASCE/SEI 7–10. Reston, VA. 

Boissonnade, A. 2000. Development of a Probabilistic Tornado Wind Hazard Model for the Continental 

United States. Vol. 1. Lawrence Livermore National Laboratory. Prepared for the U.S. Department 

of Energy. Washington, DC. 

City of Joplin. 1992. Council Bill 92–218, Ordinance 93–6 Amendments to the BOCA National 

Building Code. 

City of Joplin. 2011. Council Bill 2011–024, Ordinance Amendments to the International Residential 

Code. Ordinance No. 2011–142 (August 2011). 

City of Joplin Code of Ordinances. 2008. Part II–Code of Ordinances, Chapter 26–Buildings and 

Building Regulations, Article XIV–Registration Statement. Ordinance No. 2008–068 (May 2008). 

DOE (U.S. Department of Energy). 2002. Natural Phenomena Hazards Design and Evaluation Criteria 

for Department of Energy Facilities. DOE–STD–1020–2002. Washington, DC, January. 

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Chapter 3 

FEMA (Federal Emergency Management Agency). 2007a. Design Guide for Improving Critical Facility 

Safety from Flooding and High Winds. Risk Management Series. FEMA 543. Washington, DC, 

January. 

FEMA (Federal Emergency Management Agency). 2007b. Design Guide for Improving Hospital Safety 

in Earthquakes, Floods, and High Winds. Risk Management Series. FEMA 577. Washington, DC, 

June. 

FEMA (Federal Emergency Management Agency). 2008a. Taking Shelter from the Storm: Building a 

Safe Room for Your Home or Small Business. FEMA P–320, Third Edition. Washington, DC, 

August. 

FEMA (Federal Emergency Management Agency). 2008b. Design and Construction Guidance for 

Community Safe Rooms. FEMA P–361, Second Edition. Washington, DC, August. 

FEMA (Federal Emergency Management Agency). 2009. Tornado Protection: Selecting Refuge Areas 

in Buildings. FEMA P–431, Second Edition. Washington, DC, October. 

FEMA (Federal Emergency Management Agency). 2010. Design Guide for Improving School Safety in 

Earthquakes, Floods, and High Winds. Risk Management Series. FEMA P–424. Washington, DC, 

December. 

FEMA (Federal Emergency Management Agency). 2012. Spring 2011 Tornadoes: April 25–28 and May 

22, Building Performance Observations, Recommendations, and Technical Guidance. Mitigation 

Assessment Team Report. FEMA P–908. Washington, DC, May. 

FM Global. 2011. Hazard Assessment Mercy St. John’s Regional Medical Center Joplin, Missouri. St. 

Louis, MO, June. 

Fujita, T. T. 1971. Proposed Characterization of Tornadoes and Hurricanes by Area and Intensity. 

SMRP Research Paper No. 91. University of Illinois. Champaign–Urbana, IL. 

ICBO (International Conference of Building Officials). 1988. Uniform Building Code. UBC–1988. 

ICC (International Code Council). 2012a. International Building Code. Falls Church, VA. 

ICC (International Code Council). 2012b. International Residential Code for One– and Two–Family 

Dwellings. Falls Church, VA. 

ICC/NSSA (International Code Council/National Storm Shelter Association). 2008. ICC/NSSA Standard 

for the Design and Construction of Storm Shelters. ICC 500–2008, American National Standard. 

Washington, DC, June. 

LaRue, J. 2011. Joplin Missouri Tornado Damage Assessment, St. John’s Regional Medical Center. 

HKS Inc. June 21. 

NFPA (National Fire Protection Association). 2012. Building Construction and Safety Code. NFPA 

5000. Quincy, MA. 

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Chapter 3 

NIST (National Institute of Standards and Technology). 2006. Performance of Physical Structures in 

Hurricane Katrina and Hurricane Rita: A Reconnaissance Report. NIST Technical Note 1476. 

Gaithersburg, MD, June. 

NIST (National Institute of Standards and Technology), 2013. Preliminary Reconnaissance of the May 

20, 2013, Newcastle-Moore Tornado in Oklahoma. NIST Special Publication 1164. Gaithersburg, 

MD, December. 

NRC (U.S. Nuclear Regulatory Commission). 1974. Design Basis Tornado and Tornado Missiles for 

Nuclear Power Plants. NRC Regulatory Guide (NRC/RG) 1.76. Washington, DC. 

NRC (U.S. Nuclear Regulatory Commission). 2007. Design Basis Tornado and Tornado Missiles for 

Nuclear Power Plants. NRC Regulatory Guide (NRC/RG) 1.76. Washington, DC. 

PCA (Portland Cement Association). 1987. Connections for Tilt–Up Wall Construction. 

PCI (Precast/Prestressed Concrete Institute) Concrete Handbook Committee. 1999. PCI Design 

Handbook: Precast and Prestressed Concrete. Fifth Edition. Precast/Prestressed Concrete Institute. 

Chicago, IL, April. 

Ramsdell, J. V., J. P. Rishel. 2007. Tornado Climatology of the Contiguous United States. 

NUREG/CR–4461, Rev. 2. Pacific Northwest National Laboratory. Prepared for the U.S. Nuclear 

Regulatory Commission. Washington, DC, February. 

SEAKM (Structural Engineers Association of Kansas and Missouri). 2012. Investigations and 

Recommendations based on the May 22, 2011 Joplin, Missouri Tornado. May. Available at 

www.seakm.com/. 

SSE, Inc. 2011. Emergency Rapid Structural Condition Assessment—St. John’s Regional Medical

Center, 2727 McClelland Boulevard, Joplin, MO 64804–1694 and Associated Facilities. SSE Project 

No. 2011054. St. Louis, MO, June 3. 

TCA (Tilt–Up Concrete Association) Natural Disaster Task Force. 2012. Analysis of Damage from 

Historic Tornado in Joplin, Missouri, U.S.A. on May 22, 2011: A Report to the Technical Committee 

of the Tilt–Up Concrete Association. Report 201–12–01. Tilt–Up Concrete Association. Mount 

Vernon, IA, January 12. 

Wind Science and Engineering Center. 2006. A Recommendation for an Enhanced Fujita Scale (EF– 

Scale). Texas Tech University. Lubbock, TX. 

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4.1 

Chapter 4 

EMERGENCY COMMUNICATIONS, PUBLIC RESPONSE, AND TORNADO 

DEATHS AND INJURIES
	

The Missouri State Police Department attributed 161 deaths120 and the City of Joplin attributed more than 

1,000 injuries121 to the tornado that struck Joplin, Missouri, on May 22, 2011. With the tornado hazard 

and the performance of buildings already described, the question remains as to why this tornado produced 

the largest death toll for a single tornado since record keeping began in 1950. The objective of Chapter 4 

is to describe the pattern, locations, and causes of the fatalities and injuries attributed to this tornado, and 

to examine the associated emergency communications and public response. This chapter provides an 

understanding of the reported behavior of individuals exposed to the effects of the May 22, 2011, Joplin 

tornado, and of the factors that influenced survival or death. Survivability is analyzed in the context of 

protective action behavior (whether, and where, people took shelter), the performance of the buildings 

used as shelters, and the environmental conditions to which people were exposed. The purpose of this 

portion of the investigation is to identify recommendations relating to emergency communication, 

building and shelter performance, and public training or education that can improve public safety in future 

tornadoes. 

This chapter will cover a number of topics related to emergency communications, public response, and 

the resulting tornado casualties. These topics include the following: (1) the historical research record on 

public warning response in disasters, (2) an overview of the data collected to investigate the behavior and 

fate of individuals affected by this tornado, (3) a discussion of the conditions of Joplin, MO before the 

tornado hit, including emergency communications, emergency procedures for tornadoes, and previous 

tornado history, (4) a timeline of the tornado that struck Joplin on May 22, 2011, and the public’s 

response to the tornado, (5) a discussion of the casualties that resulted from the tornado, and (6) the 

identification of factors that likely caused the impact–related deaths and severe injuries that resulted from 

the May 22, 2011, Joplin tornado—both outside and inside of structures. 

PUBLIC WARNING RESPONSE IN DISASTERS 

The purpose of this section is to summarize what is known about public response to alerts and warnings 

for imminent disasters based on the historical research record. Before research is presented, the 

difference between an alert and a warning should be made clear. An alert is used to gain people’s 

attention and is often provided separately from the warning message. A warning message is meant to 

provide information to the public on the state of the emergency and what they are supposed to do in 

response to this emergency. 

120 A list of the deceased was sent to NIST on June 20, 2011, which included the name, date of birth, and home address of each 

decedent, as well as where the death occurred, the type of injuries that led to the fatality, and the name of the associated funeral 

home. 121 Community Press Kit issued for the Day of Unity observance, May 22, 2012, http://www.joplintornadoanniversary.com/ 

resources/community–press–kit.pdf. 

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Chapter 4 

Research has shown that the response of an individual during an emergency can be characterized as a 

decision–making process in which people receive information from their environment, interpret that 

information, and respond based upon their interpretations (Lindell and Perry 2004). The process of 

decision–making begins when people are first presented with cues from their environment. In a tornado, 

specifically, these cues can consist of a siren, radio or television broadcasts, calls from loved ones, or 

even the presence of the tornado bearing down upon them. The introduction of these cues initiates a 

series of processes that must occur in order for the individual to respond. A simplified version of this 

process is presented here: 

1.	 Perception: the individual must perceive or receive the cue(s); e.g., a visual signal must be seen or 

an audible signal or warning must be heard. 

2.	 Attention: the individual must pay attention to or take note of the cue(s). 

3.	 Comprehension: the individual must comprehend the cue(s) and/or information that is being 

conveyed. 

4.	 Threat identification/Believing: the individual must believe that the incident suggested by the 

cues and/or information is a credible threat. 

5.	 Threat perception/Personalizing: the individual must personalize the threat (i.e., feel that the 

incident is a threat to him/her) and feel that protective action is required; i.e., something needs to 

be done. 

Once the individual engages in each stage of the process and in turn, personalizes the risk, the individual 

engages in a decision–making process to identify 1) what can be done to achieve protection, and 2) the 

best available method for achieving protection. 

The historical research record supports the provision of information (i.e., providing a warning message 

rather than simply an alert) as a method to enhance public protective action response. When issuing 

emergency messages, there are five key aspects of a successful warning message. These five aspects are 

presented here, with associated references: 

	 The message delivered by a credible source (Drabek and Boggs 1968; Mileti and Beck 1975; 

Mileti and Darlington 1995; Sellnow et al. 2012; Vihalemm, Kiisel and Harro–Loit 2012; 

Stephens, Barrett and Mahometa 2013); 

 Guidance or telling people what to do to protect themselves (Sorensen 1991; Mayhorn and 

McLaughlin 2012); 

 The hazard or explaining why they should act (Mallett, Vaught and Brnich 1993; Neuwirth, 

Dunwood and Griffin 2000; Sellnow et al. 2012); 

 The location, i.e., informing the public about who should act in terms of the physical location at 

risk (Mileti and Fitzpatrick 1991); and, 

 Time or telling the public by when they should have completed taking the protective action 

(Sorensen, Shumpert and Vogt 2004). 

Similarly, there are five key factors, unrelated to alerts and warnings that can enhance public protective 

action response in disasters. The five key factors are listed here, with associated references: 

	 The presence of social and/or physical cues. Physical cues are cues from the physical 

environment that an individual can hear, feel, see, smell or taste (if applicable), and social cues 

236 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

4.2 

Chapter 4 

are those that come from other people whom the individual communicates with or observes 

(Kuligowski and Mileti 2009; Mileti and O’Brien 1993); 

	 Statuses (e.g., the individual’s income, education, occupation, age, race, gender, ethnicity, and 

country of origin). In other words, people with certain types of statuses, for example, older 

individuals rather than younger individuals (Proulx and Pineau 1996), are more likely to take 

protective actions in a disaster (Fothergill 1998; Fahy and Proulx 1997); 

	 Roles or the social position held within a personal or professional environment (e.g., mother, 

manager, fire fighter, etc.). Similarly, people with certain roles, for example, managers (e.g., 

Kuligowski 2013), are more likely to take protective actions in a disaster; 

 Having experience with and/or knowledge/training on response to disasters or situations similar 

to emergency conditions (Gershon et al. 2007; Perry and Lindell 1986); and 

 Having pre–event risk perceptions (i.e., believing in a higher likelihood of a disaster occurring in 

the future) (Lindell and Perry 2004; Slovic et al. 2004). 

The findings specific to tornado research replicate the historical research record of public response to 

alerts and warnings across many different hazards types. For example, tornado research has shown that 

understanding the situation and what to do about it (Liu et al. 1996; Alberta Public Safety Services 1991) 

increases an individual’s personalization, or perception, of risk (i.e., stage five in the decision–making 

model). Also, tornado research has identified factors, unrelated to alerts and warnings, shown to increase 

an individual’s perception of risk, and in turn, the likelihood of his/her response. These are listed here, 

categorized by the factors discussed above: 

	 Physical and social cues: 

o	 Receiving multiple, consistent cues that lead to the conclusion that a tornado is a threat 

(NWS 2009; Hammer and Schmidlin 2002); 

o	 Achieving visual confirmation of the storm (NWS 1993a; NWS 1993b); 

o	 Seeing others taking protective actions (NWS 2009); 

o	 Receiving face–to–face or informal warnings (i.e., from family and friends) (NWS 2009; 

Colorado Department of Public Safety 1991); 

	 Having experience: Personal experience with hazards and disasters (Hodler 1982), including 

experience that is perceived as negative in nature (Kuligowski 2011). 

DATA COLLECTION 

The tornado damaged an area within the City of Joplin having an estimated population of 20,820 (U.S. 

Census Bureau 2011). In order to investigate the behavior and fate of individuals affected by this 

tornado—both those who survived and those who did not—three sets of information were collected. 

First, data were collected on the response of the public before the tornado hit. Here, it was of interest to 

understand how individuals (both those who survived and those who did not) became aware that a tornado 

was imminent and the ways in which they responded to this awareness. Second, information was 

collected on the consequences of the tornado for the people exposed, i.e., the casualties (both injuries and 

fatalities) resulting from the event. These data included, but were not limited to, the locations where 

people were injured (or killed), the causes of the casualties (if known), and the nature of people’s injuries 

(some of which led to death). Finally, data were collected from emergency response personnel to learn 

about the pre–tornado emergency plans of the City of Joplin and Jasper County and how these plans were 

implemented on May 22, 2011. These data allow for observations to be made on whether the tornado 

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Chapter 4 

emergency system (including communications and procedures) operated as intended, and the 

identification of possible improvements that could save lives in future tornadoes. 

4.2.1 Data on Public Response 

Information on the public response before the tornado hit was obtained primarily through qualitative 

interviews. Several factors were taken into account when selecting the best method for collecting data on 

public response. Based on our understanding of how individuals make decisions during disasters, it was 

of interest to identify not only the information received by individuals and their responses to this 

information, but also the meanings that they developed (i.e., their situational awareness) and how these 

meanings influenced decision–making processes during the storm. Therefore, qualitative interviews were 

conducted via telephone or face–to–face meetings with survivors and friends and families of victims who 

experienced the storm. These interviews were conducted to collect detailed descriptions of individuals’ 

experiences with their environment and the meanings that they generated as the tornado event was 

unfolding around them. 

Interviewees were recruited for participation in the NIST investigation by several means. NIST published 

a NIST Tech Beat newsletter article describing the study that was posted on the NIST website and emailed 

to subscribers of NIST email alerts.122 While in Joplin, interviewers posted flyers in and around the 

Joplin area and participated in interviews with Joplin area news outlets, including newspaper, television, 

and radio sources, which resulted in feature stories on the NIST technical investigation. Also, assistance 

in getting the word out was provided by several emergency officials and business or faith–based 

organizations within the Joplin area. In each recruitment strategy, NIST asked survivors and family or 

friends of victims of the May 22, 2011, Joplin tornado to please call, text, or e–mail so that NIST might 

interview them about their tornado–related experiences. NIST interviewers also called and traveled to 

local businesses to ask management about their interest in and availability for interviews. This very 

visible public recruitment enabled NIST to interview willing participants from a variety of geographic 

locations throughout the Joplin area, including some who had been displaced by the storm. Individuals 

interested in telling their stories were pre–interviewed to ensure that they in fact were located (or knew of 

someone who was located) in or near the damage path during the tornado. 

After careful consideration, it was determined that a semi–structured interviewing technique best fit the 

requirements of this investigation. Highly structured (HS) interviews contain a fixed set of questions, 

often with set response options, and are mainly used to collect quantitative data that allow for ease of data 

comparison from one interview to the next. However, a HS instrument was deemed as unfeasible in this 

investigation due to the speed at which the NIST team began instrument development and, at that time, 

the lack of systematic analysis of Joplin survivor accounts (e.g., available in the media) necessary for the 

development of this type of instrument. Unstructured interviews, on the other hand, are conducted more 

like a conversation between the interviewee and interviewer, where very little structure is provided by a 

question set. Unstructured interviews allow for the collection of rich, powerful descriptions of the event; 

however, very little opportunity to compare one interview response to another (which was necessary 

here). The semi–structured interviewing technique allowed for the collection of rich, detailed data on 

tornado experiences (and the ways in which these experiences are interpreted by the interviewee) as well 

122 NIST Tech Beat article: “NIST Seeks Help in Understanding Public Response to Joplin Tornado”
 

(www.nist.gov/el/disasterstudies/joplin–101311.cfm).
 

238 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

as the opportunity to compare similar types of data. Additionally, this interviewing technique allowed for 

the discovery of phenomena and causal patterns that were not originally anticipated, and helped 

interviewees retrieve more comprehensive and accurate memories of incidents. 

This semi–structured approach was conducted in two phases. In the first phase, respondents were asked 

to describe their experiences from the time when they first became aware that something was wrong until 

the moment when they responded to the disaster, such as by evacuating a building or sheltering in place. 

They were asked to speak freely about their experiences (what they saw, what they did, what they were 

thinking). The second phase was more structured, in that the interviewer asked follow–up or clarifying 

questions about important topics from a pre–established list of probing questions. The list of questions 

was developed by collecting and analyzing over 100 media accounts of May 22, 2011, Joplin tornado 

eyewitness survivor stories as well as by conducting some brief, initial interviews (17 in total) with 

survivors 5 days after the storm. The probing questions were used to ask about the following topics: 

awareness of the event, emergency communications received, actions taken, risk perceptions, pre–existing 

or event–driven injuries or impairments, previous experiences with severe storms, and familiarity with 

and perspectives on the emergency communications system in Joplin. 

In total, NIST interviewed 168 survivors of the tornado, through a combination of in–person and 

telephone interviews.123 The respondents ranged in age from 18 to 88, with a mean age of 51. Gender 

was also distributed, with women making up 59 percent of the sample. A geographic analysis of where 

respondents were located during the tornado showed that the sample was well distributed across the 

tornado’s path through Joplin, with a small percentage located outside the area of tornado damage (i.e., 

EF0 to EF4 wind speeds zones). Interviewees were also widely distributed by physical setting during the 

storm: approximately 67 percent were at their or someone else’s home (or apartment), 14 percent were in 

a private business, 7 percent were driving or stopped in a vehicle, 5 percent were in St. John’s Regional 

Medical Center (SJRMC), 5 percent were in Joplin area churches, and the remaining 2 percent of the 

sample were either located outside of buildings or did not specifically state where they were located as the 

storm struck. 

A portion of the survivor interviews (10 percent) was conducted with managers and employees of local 

businesses and institutions, including individuals in positions of authority at SJRMC. Information on 

organization–wide tornado emergency procedures, structural damage to facilities, sheltering options, and 

previous experience with emergencies was obtained from these interviews. Additional information on 

emergency procedures and tornado response was obtained from two interviews with SJRMC 

administrators and one interview with a senior manager of corporate security at the Home Depot. 

However, these three interviews were not counted among the total of 168 Joplin survivor interviews 

because, during the storm, these interviewees were not located within the area in Joplin exposed to the 

tornado. 

A portion of the survivor interviews provided information regarding individuals who died from the storm. 

Seventeen of the 168 survivor interviewees (10 percent) provided information about the circumstances of 

a decedent before the tornado hit. In addition, two individuals not included in the 168 interviewees were 

interviewed by NIST regarding the circumstances of two fatalities of this storm, even though the 

interviewees, themselves, were not directly exposed to the tornado. 

123 The 168 participants also included 11 survivors who e–mailed their stories to NIST. 

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Chapter 4 

Finally, a portion of the 168 interviewees was injured by the storm. A total of 16 of the 168 interviewees 

specifically mentioned suffering a major, longer–term injury from this storm that required hospital 

attention. Other interviewees sustained only minor injuries or no injuries at all. 

Relevant data were also collected by the National Weather Service (NWS), via face–to–face interviews 

selected using a convenience sampling technique, and the interviewers’ written notes were provided to 

NIST in electronic form. No personally identifiable information was provided to NIST from any of the 

NWS interviews. The NWS also conducted interviews with businesses that suffered damage in the storm, 

to inquire about emergency procedures and the steps taken on May 22nd to protect people from harm. 

Most interview information collected by the NWS was verified by NIST via interviews with others in 

similar circumstances before being included in this report. 

The interviews conducted by NIST constituted a “convenience sample,” because they were performed 

with specific persons of interest, persons who volunteered to participate, or interviewees who were 

suggested to NIST by those who volunteered. There are limitations associated with this interview 

sampling strategy. The development of a convenience sample limits the ability of the researcher or 

analyst to generalize the findings to others affected by this tornado (others to whom NIST did not speak) 

as well as to other tornado disasters. These limitations on the ability to generalize were reduced by 

ensuring that certain topics (i.e., experiences with the tornado on May 22, options for protective action, 

and previous experiences with and perspectives on warning systems and tornadoes) were saturated, in that 

similar information was consistently collected as the interviews continued. Additionally, NIST analysts 

ensured that the convenience sample varied by age, geographic location throughout the damage path, and 

physical setting during the event (i.e., home, business, outdoors, or vehicle), further reducing the 

limitations of this dataset. 

Data on decedents’ experiences before and during the tornado were an important aspect of this study. 

Therefore, attempts were made to interview family members and friends of the victims to obtain 

information on their understanding of the event and the decedents’ responses. Additional information on 

public response, especially in relation to the deceased, was obtained from the following sources: 

newspaper articles; books (Kansas City Star 2011; Joplin Globe 2011; Turner and Hacker 2011); social 

media, including Facebook accounts for tornado recovery and decedents’ profile pages; and obituaries. 

This data collection effort is described in further detail in Sec. 4.2.2. 

4.2.2 Data on Consequences of the Tornado—Injuries and Deaths 

Information on casualties was also obtained to identify the pattern, locations, and causes of fatalities and 

injuries (the main objective of this chapter). To understand the circumstances surrounding the deaths, 

NIST collected data and information from its interviews with friends and families of tornado victims 

(described above), the Missouri State Police Department, the American Red Cross (Disaster Health 

Services), Facebook pages of the deceased and pages dedicated to the Joplin recovery, stories recorded in 

three books published on the tragedy (Kansas City Star 2011; Joplin Globe 2011; Turner and Hacker 

2011), a LexisNexis obituary search, and death certificates for all victims of the tornado (provided to 

NIST by the Missouri Department of Health and Senior Services (MDHSS), the Oklahoma State 

Department of Health, and the Kansas Department of Health and Environment’s Office of Vital 

Statistics). The death certificates provided the most information on the deceased, including place of 

240 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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injury, time of injury, description of injury, place of death, time of death, cause of death, gender, 

occupation, education, and marital status. 

To understand the circumstances of the more than 1,000 injuries resulting from this tornado, two datasets 

were obtained. Both datasets were provided to NIST by the MDHSS Division of Community and Public 

Health. The first dataset, entitled ESSENCE, included syndromic surveillance data, or data obtained from 

a systematic process of timely data collection and analysis in order to detect and characterize outbreaks of 

disease in humans. The ESSENCE database on the May 22, 2011, Joplin tornado injuries contains 762 

records from residents of Jasper and Newton Counties and 114 records from persons residing outside of 

these counties. The dataset provides the following data on each injured party: gender, age range, and 

category of the chief complaint (i.e., the reason the injured person went to the hospital). 

The second injury–related dataset used by NIST was collected by the U.S. Centers for Disease Control 

and Prevention (CDC) for the MDHSS to investigate a number of reports of fungal skin infection in 

people who were injured by the May 22, 2011, Joplin tornado (this investigation was referred to as the 

CDC EPI–Aid Study). The CDC dataset included injury and personal data from a total of 87 

individuals124 randomly selected by the CDC from the ESSENCE dataset previously described. The data 

provided to NIST were acquired by the CDC from both medical record chart abstraction and face–to–face 

interviews. The hospital chart abstraction was based upon a list of 62 questions, which addressed the 

following topics: address, date of wound/injury, date/time of receipt of medical attention, hospital 

admission history, initial admit diagnosis, intensive care unit (ICU) admittance (and number of days in 

hospital/ICU), intubation records, evidence (if any) of fungal growth, additional details about the fungal 

growth (not used by NIST), evidence of other types of wounds, total number of wounds, location and 

context of wounds, other injuries noted in addition to wounds, pre–tornado risk factors, treatment 

received, and outcomes (including information on deaths). Experiential data from the tornado event were 

collected by the CDC via face–to–face interviews with the injured (or family/friends of the injured). 

Interviewees were asked to describe what happened from the time the tornado started until the time the 

injured individual sought medical care, and to provide answers to more specific questions about their 

location during the storm, the type of structure in which he or she was located (including its construction 

type and information about the foundation and sheltering options, if in a home), the type of damage that 

occurred to the structure, and the methods the injured individual used to obtain protection from the storm 

(if any). 

There are limitations to the data collected on injuries resulting from the May 22, 2011, Joplin tornado. 

First, the ESSENCE dataset focuses on individuals who visited the emergency room or used the 

emergency department services of a hospital. The ESSENCE dataset contained a total of 876 records, 

whereas other sources have estimated over 1,000 injuries resulting from this tornado125 . Since every 

injury might not have required emergency hospital services, it is likely that injuries occurred that were not 

included in this dataset, and thus, not obtained by NIST. Second, these datasets were not collected by 

NIST and, therefore, did not contain all of the information sought by NIST in its investigation. For 

example, the causes of the injuries listed in the ESSENCE database were very general in nature, making 

124 Data on only 71 injured participants from this dataset were used by NIST because some of those in the original 87 were 

deceased, and thus were included in the fatalities sample, or were provided to NIST with insufficient information for further 

analysis. 125 Community Press Kit issued for the Day of Unity observance, May 22, 2012, http://www.joplintornadoanniversary.com/ 

resources/community–press–kit.pdf. 

NIST NCSTAR 3, Joplin Tornado Investigation 241 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

them difficult to use in this investigation. Also, and more importantly, the ESSENCE database did not 

contain information about where each individual was located when he or she was injured, limiting the 

analysis that NIST could perform with this larger dataset of 876 injured individuals. Therefore, NIST 

primarily used the CDC dataset (i.e., the set of 71 out of the original 87 injured persons). However, there 

were also limitations associated with the CDC dataset, including the fact that the individuals were 

selected from the ESSENCE database, which had not been finalized when the CDC study was performed. 

Due to the limitations of the injury data, NIST used these data only to support the findings presented on 

fatalities, rather than to derive findings about injuries. 

4.2.3 Data on Emergency Response 

In addition to data collection efforts focused on public response and tornado consequences, investigative 

interviews were also held with emergency response personnel. These interviews were conducted as 

unstructured interviews, i.e., without a set of prescribed questions, that focused on a particular topic about 

which the interviewee had expertise. Emergency response personnel were asked about Joplin–Jasper 

County’s tornado emergency communications system at the time of the May 22, 2011, Joplin tornado, its 

method of operation, and emergency plans specifying appropriate public protective actions in tornadoes. 

Also of interest was any information on Joplin’s history with tornadoes and severe storms, including the 

number of times that sirens sounded (in the past) on a yearly basis. Interviews were held with 

representatives from the Joplin–Jasper County Emergency Management office, the City of Joplin Fire 

Department, the City of Joplin Police Department, and Missouri’s State Emergency Management Agency 

(SEMA). In addition to the information obtained in interviews, NIST obtained copies of the City of 

Joplin’s and Jasper County’s local emergency operations plans. 

4.3 JOPLIN, MISSOURI, BEFORE THE TORNADO OF MAY 22, 2011 

Joplin, Missouri, is a relatively small city (approximately 30 square miles) situated within Jasper and 

Newton Counties, which are located in the southwestern part of Missouri. Jasper County is bordered by 

Newton (to the south), Barton (to the north), and Dade and Lawrence Counties (to the east), and by the 

State of Kansas to the west. See Chapter 1, Fig. 1–1 and 1–2 for maps of Joplin and surrounding areas. 

Joplin is the fourth largest metropolitan area in Missouri, with a population of 50,150 (U.S. Census 

Bureau 2010). 

According to the City of Joplin’s and Jasper County’s local emergency operations plans, Joplin and 

Jasper County are exposed to many types of hazards. Possible natural hazards, in addition to tornadoes, 

are flooding, drought, wildfires, and severe winter storms. In any type of emergency, it is the 

responsibility of the local government to provide for public safety in the event of a disaster. If the 

emergency exceeds the local government’s capability to respond, assistance is then requested from the 

State government. The City of Joplin and Jasper County created emergency management organizations 

that are responsible for the preparation and implementation of emergency management functions for their 

jurisdictions.126 

126 Keith Stammer, emergency manager for Joplin/Jasper County, personal communication, 2013. 

242 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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The Joplin–Jasper County Emergency Management office was (and still is) located in the business district 

of Joplin, an area not damaged by the tornado. It was established based upon Missouri Revised Statutes 

Chapter 44, Civil Defense, Sec. 44.080, which states that “All political subdivisions shall establish a local 

emergency management organization.”

127 A political subdivision can be defined as a fire district, village, 

town, city, or county. There are approximately 1,400 political subdivisions within the State of 

Missouri.128 Most political subdivisions appoint their fire chief as emergency manager, and others have 

an emergency manager who serves on a part–time basis. It is the role of the emergency manager of each 

subdivision to make decisions on response plans, recovery procedures, the emergency communication 

system, and when to activate this system in emergencies. 

Even though the emergency manager for the City of Joplin holds the title of “Joplin–Jasper County 

Emergency Manager,” his or her authority on emergency communications and procedures is limited to the 

City of Joplin. (The city provides, under a contract with the county, emergency management services to 

the county at large for those political subdivisions that do not have dedicated emergency management 

officials or those that require guidance.) Therefore, every political subdivision within Jasper County can 

potentially have significantly different emergency communication systems and emergency plans and 

procedures. 

4.3.1 Emergency Communications—Outdoor Siren Systems 

Prior to May 22, 2011, the City of Joplin had developed emergency plans on how to alert and warn 

individuals in the event of a tornado (SEMA et al. 2011). Joplin and the 11 other communities within 

Jasper County had outdoor siren devices. Such devices consist of a network of sirens (also known as civil 

defense or air raid sirens) stationed at multiple points throughout the county, city, or community that 

produce a pattern of sounds to alert individuals of impending hazards. An outdoor siren system can also 

include loudspeakers to broadcast voices, horns, or whistles. Figure 4–1 shows the type of siren used in 

the Joplin area, model #2001–130 from the Federal Signal Company. These sirens were not equipped 

with the capability to disseminate voice announcements to the community, thus the system existed as an 

alerting system only (i.e., without the capability of providing warning information to the public). 

There were 25 sirens in the City of Joplin’s outdoor system; 23 were located within the City of Joplin, 

and one each was located in Duenweg (siren located at 20th and Duquesne) and the Village of Airport 

Drive (note: each of these sirens belongs to the respective city, but they are tied into the Joplin system). If 

a decision were made to sound the sirens for an emergency affecting the Joplin area, all 25 sirens 

connected to Joplin’s system sounded simultaneously. However, there was no interconnection between 

the sirens in Joplin’s system and those located in other parts of Jasper County. Siren locations for the 

City of Joplin are shown in Fig. 4–2. These sirens were spaced at a radius of 1 mile, per guidance 

provided by the Federal Emergency Management Agency (FEMA) guide CPG 1–17, Outdoor Warning 

Systems Guide (1980), and were set at a decibel rating of 130 dB at 100 ft. 

127 Missouri Revised Statutes, Chapter 44, Civil Defense, Section 44.080 (www.moga.mo.gov/statutes/C000–099/ 

0440000080.HTM). 128 Keith Stammer, emergency manager for Joplin/Jasper County, personal communication, 2013. 

NIST NCSTAR 3, Joplin Tornado Investigation 243 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

Figure 4–1. Model #2001–130 

Siren from the Federal Signal 

Company. 

Figure 4–2. Siren locations for 

the City of Joplin. 

During a tornado emergency, the Joplin Communication Center Dispatch, which is located in the Joplin– 

Jasper County Emergency Operations Center (EOC), is responsible for activating the 25 outdoor sirens. 

The sirens can be sounded only after the communications operator has been notified by weather monitor, 

weather pager, teletype, or public safety personnel that a “tornado has been sighted or a tornado warning 

has been issued by the NWS for Jasper, Newton, or Cherokee County. The sirens will also be sounded if 

sustained winds are 75 mph or higher” (SEMA et al. 2011, Annex B). The policy, according to the 

Joplin–Jasper County Emergency Management director, is to sound the sirens as early as possible, and if 

conditions look close to those specified above, he or she will decide to sound them.129 Joplin’s outdoor 

siren system is not sounded for any types of emergencies other than tornadoes or severe windstorms. 

For activating the sirens anywhere within Jasper County, there are two 9–1–1 call centers: one in Joplin 

(located in the Joplin EOC) and one in Carthage (Jasco 911). Political subdivisions within Jasper County 

can either operate their sirens locally or through the Carthage call center. Usually, sirens are activated by 

the authorities in each political subdivision, i.e., the police chief or fire chief physically activates the 

sirens. 

FEMA’s Outdoor Warning Systems Guide was the only guidance that NIST found on the use and testing 

of outdoor warning (or siren) systems. FEMA updated this guide in 2006 (FEMA 1980, 2006). These 

FEMA documents suggest that, for a local incident (e.g., a tornado), an attention or alert warning should 

be given by sounding sirens, horns, or other sound–producing devices continuously for 3 min to 5 min. 

129 Keith Stammer, emergency manager for Joplin/Jasper County, personal communication, 2011. 

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At the time of the May 22, 2011, Joplin tornado, the practice in Joplin was to alert the public of an 

emergency by sounding the outdoor siren system continuously for 3 min and then turning off the sirens. 

The City of Joplin’s system was not designed to issue an “all–clear” message via the sirens or any kind of 

public address announcement. Additionally, the FEMA guidance suggests that the outdoor siren system 

be tested on a monthly basis, and that during the test, the test signal should sound for no more than 1 min 

in the “Attention/Alert” mode (i.e., continuous sounding). This initial test signal should be followed by 1 

min of silence, and then the test should be concluded by sounding the “Attack” warning (i.e., a warbling 

sound) for no more than 1 min. In Joplin, there was no difference in sound or tone for different types of 

wind events (i.e., the sirens were sounded in the same manner for straight–line winds and for tornadic, 

circular winds). In addition, the sirens were tested on a weekly basis in Joplin, weather permitting, at 10 

a.m. on Mondays. During the test, the sirens were activated in tornado/windstorm mode (i.e., sounded 

continuously) for a period of 1 min and then turned off. 

The FEMA documents also provide guidance on the meaning of the attention/alert tone, stating that this 

mode is supposed to signal that all persons in the area should turn on the radio or television and listen for 

essential emergency information. In Joplin, the siren system was not meant to alert people located inside 

of buildings. Rather, the siren system was meant to alert people located outside to take cover, to hide, or 

130, 131 to move into buildings (if possible), preferably sturdy buildings with a secure area. If people 

indoors wished to receive alerts, the Joplin–Jasper County emergency plans suggested the use of a 

weather radio. 

NIST reviewed how use of the outdoor siren system in Joplin compared with use of similar systems in 

other communities in Missouri and across the United States. Information from the emergency 

management websites of more than 75 U.S. counties, cities, and towns equipped with outdoor (siren) 

systems was compared, showing that use of these systems differs in four main ways from Joplin’s 

operations at the time of the May 22, 2011, Joplin tornado: 

	 Joplin’s siren system was primarily used for tornadoes and other windstorm events, while some 

communities throughout the nation use these systems for other types of disasters, including 

national security events, chemical spills, and tsunamis. 

	 Joplin relied primarily on information from the NWS, while some communities rely only on local 

officials and/or trained weather spotters to decide when to activate the siren system. 

	 Differences exist in the sounds disseminated by sirens from community to community. Joplin 

used a continuous tone over a finite, 3 min time period, whereas other communities sound their 

sirens continuously using a repeating time interval (e.g., sound for 3 min, off for 8 min, sound for 

3 min). 

	 Joplin used the same continuous tone for tornadoes and other windstorm events; however, other 

communities alternate different types of tones (continuous versus wavering, for example) and 

tone patterns (see bullet above) for different types of emergencies. 

130 Keith Stammer, emergency manager for Joplin/Jasper County, personal communication, 2011. 

131 Randy Scrivner, emergency manager with the State of Missouri, personal communication, 2011. 

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Chapter 4 

This analysis also revealed that tornado communication systems and their uses often vary within the same 

State, and even among adjacent communities, and that some communities, especially smaller towns and 

rural areas (even within tornado–prone regions), do not have such systems. The variability in the design 

and use of emergency communication systems could make it difficult for citizens to understand, from city 

to city and even across cities within the same area, what type of disaster is imminent and what actions 

should be taken in response. This is especially the case among systems that lack explanatory public 

address announcement capability. Traveling to locations where different emergency communication 

procedures exist can cause confusion and the potential for more severe consequences, like injury and 

death. See Appendix K for more detailed findings from this review. 

One possible reason for the differences in outdoor warning, alert, or siren system use among communities 

is the lack of Federal, State, or industry standards or requirements on system use and subsequent public 

responses. National codes and standards relevant to tornado siren systems mainly provide requirements 

for the construction, installation, and maintenance of these systems. Whereas previous guidance was 

provided in the annex, only the latest edition of the National Fire Protection Association’s (NFPA) 

National Fire Alarm and Signaling Code (2013) provides general requirements on message writing and 

dissemination for emergencies (not specific to tornadoes). See Appendix L for additional details on codes 

and standards for outdoor tornado warning systems. With no Federal, State, or industry requirements and 

very little guidance, outdoor siren policies vary from community to community throughout the United 

States (Coleman et al. 2011). 

4.3.2 Emergency Communications—Other Modes of Communication 

In addition to the outdoor siren system, prior to May 22, 2011, Joplin had access to additional 

communication modes for tornadoes. First, the Joplin Police Department and Jasper County 9–1–1 

centers had “Reverse 9–1–1” capabilities. Reverse 9–1–1 calling was developed to allow emergency 

management agencies (at the local level) to contact individual households via landline phone systems and 

cell phones to warn them of impending disasters. This system uses a database of landline telephone 

numbers, cell phone numbers (only if subscribers provide them), and addresses that are each tied to a 

specific geographic location. Emergency managers use this information to deliver recorded emergency 

notifications to a selected set of telephone service subscribers, based upon the location of the disaster. 

Even though Joplin was equipped with this technology, the emergency manager noted that the local phone 

switches could not always handle the volume of calls necessary in a timely manner and it had taken up to 

3 hours to get emergency calls out in previous uses. Therefore, this technology was not used on May 22, 

2011.132 

All three of the local television stations in the Joplin area had mobile web opt–in accounts that sent out 

emergency information to the communication devices of individual subscribers in the event of an 

emergency. These mobile warning services require that individuals sign up to receive the alerts and 

warnings, which can often be delivered to as many devices as the subscriber chooses, including e–mail– 

or text–enabled devices. 

132 Keith Stammer, emergency manager for Joplin/Jasper County, personal communication, 2011. 

246 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

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Individuals in Joplin (especially those located indoors) could also be alerted to weather information 

through a National Oceanic and Atmospheric Administration (NOAA) weather radio (NWR). The NWR 

All Hazards Network is a network of radio stations that broadcast continuous weather and hazard 

information, including official NWS warnings, watches, and forecasts, on a 24–hour–a–day basis. The 

broadcast information comes directly from the nearest NWS local office in the form of computerized– 

voice weather broadcasts to an NWR receiver, although there are variations of this receiver device for the 

deaf or hard of hearing. It is the responsibility of individual users to voluntarily purchase this device and 

maintain it in working condition. There are no Federal, State, or local requirements for public or private 

buildings or residences to own a functioning NWR receiver. Instead, NWRs are made available for 

purchase in many retail outlets. 

For individuals with access to these media, weather information was also broadcast via radio and 

television. In some cases, meteorologists convey information directly from the NWS or from their own 

weather models, and in other cases, news anchors convey weather information provided to them from 

other sources. It should be noted that television and radio stations in the United States are under no 

obligation to provide severe weather information to the public. While the Federal Communications 

Commission licenses broadcasters to operate in the public’s interest, and most television and radio 

stations do provide severe weather information to varying degrees, there is no Federal or State law 

requiring local broadcasters to provide tornado warnings to the public before or during an emergency. 

In times of emergency, the Joplin–Jasper County Emergency Management office could also take 

advantage of communications via the Emergency Alert System (EAS).133 The EAS is a national public 

warning system requiring broadcasters, cable television systems, wireless cable systems, satellite digital 

audio radio service providers, and direct broadcast satellite providers to allow communication capability 

to the President in national emergencies. State and local authorities can also use the system to deliver 

important weather information targeted to specific areas. 

In either case, for individuals to receive emergency information via television or radio, they must be 

proactive and search for it. Emergency information disseminated via television and radio is accessed only 

when people seek it out or are already tuned into these sources for some other reason and inadvertently 

receive weather information. With that said, in most cases where information is unclear, ambiguous, or 

scarce, the public will take time to seek additional information from a variety of channels. 

Similarly, individuals in the Joplin area could have received weather information through various online 

sources, if they sought it prior to the storm. For example, the NWS provides advisory, watch, and 

warning information via various websites and e–mail and social networking accounts, such as Twitter. 

Many news and weather sites post the most current emergency messages (either directly from the NWS or 

written in their own words) as well as other emergency–related information. 

4.3.3 Sheltering Procedures for Tornadoes 

Prior to May 22, 2011, Joplin had developed guidelines on in–place sheltering for residents in the event of 

tornadoes or other types of technological or natural hazards (SEMA et al. 2011). The guidelines 

acknowledge that tornadoes present situations in which people should shelter in place. The responsibility 

133 Federal Communcations Commission: “Emergency Alert System” (http://transition.fcc.gov/pshs/services/eas/). 

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Chapter 4 

for heeding warnings and taking appropriate actions falls on individual communities and citizens. The 

emergency plans for Joplin state that, although there is no guaranteed safe place during a tornado, “the 

safest place in the home is the interior part of the basement, preferably under something sturdy, like a 

table. If a basement is not available, an inside room on the lowest floor, like a closet or bathroom with no 

windows, should be used” (SEMA et al. 2011, K–8). 

The housing stock in Joplin (especially along the tornado damage path) provided very little in the way of 

underground shelter options. Few houses (17 percent, or 1,237 out of 7,411 damaged homes located 

within the damage path) had basements, partial or full. The many near–surface mine tunnels134 and other 

unfavorable soil conditions (high water table and limestone just below the surface135) made it difficult for 

builders to include basements in many homes throughout the Joplin area. In addition, very few 

individuals invested in in–home shelters. There was, however, a significant number of homes with crawl 

spaces (80 percent, or 5,904 out of 7,411). Crawl spaces are typically located under the first floor of the 

house, sometimes but not always underground, and provide access to pipes, substructures, or other areas 

of the house not easily accessible. The height of crawl spaces can be as small as 1 ft and most crawl 

spaces are typically accessed externally (residents must go outside of the house to enter the space). 

No stand–alone or within–building public shelters were located in Joplin at the time of the tornado. This 

may have been due, at least in part, to the lengthy and complicated steps involved in obtaining a FEMA– 

funded public shelter, including showing FEMA the building schematic, developing operation and 

maintenance procedures, creating plans for notifying the public, and showing that individuals can access 

the area by car in less than 5 min travel time.136 However, there are three FEMA–funded community 

shelters located in Newton County, adjacent to Jasper County, which were built to FEMA standards. 

4.3.4 Tornado History in the Joplin Area 

Prior to 2011, the City of Joplin had experienced one tornado rated EF–2 or higher since the beginning of 

official tornado record keeping in 1950. A recorded F–2 tornado directly affected the City on May 5, 

1971. Information about this tornado was detailed in a book, which is available online (Knapp and Boone 

1971), and a summary description of this event is provided in Chapter 1 of this report. 

Although the City of Joplin had never experienced a tornado causing the levels of death and damage that 

were sustained on May 22, 2011, tornadoes were a familiar sight in the area surrounding Joplin prior to 

2011. Since 1950, 182 tornadoes rated EF–2 or higher had struck within an 80–mile radius of Joplin. 

This included three tornado events rated EF–3 or higher. The first of these occurred on April 3, 1956, 

when an F–4 tornado caused 118 injuries and likely millions of dollars in damage according to the NWS 

Storm Prediction Center (SPC) database. Second, a May 4, 2003, tornado outbreak included two 

tornadoes that were rated F–3 and passed within 25 miles of Joplin, causing 17 fatalities, 116 injuries, and 

over $95 million in damage. Third, a May 10, 2008, event consisted of two EF–4 tornadoes that were 

within the Joplin region, but outside Joplin’s city limits. These tornadoes caused a total of 43 fatalities 

and 710 injuries, and the total damage was estimated at $122 million. 

134 City of Joplin Building Official, personal communication, 2011.
 

135 Reuters, “Without basements, Joplin had scant refuge from tornado” (www.reuters.com/article/2011/05/31/us–tornado–
 

basements–idUSTRE74U6HT20110531). 

136 FEMA, personal communication, 2011. 

248 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Even more familiar than tornado events to residents of the region around Joplin has been the issuance of 

NWS tornado warnings. NWS–issued warning information is primarily disseminated to the Joplin 

population via NWRs, the EAS, television or radio broadcasts (or associated mobile–based opt–in 

services), and Internet sites, including the NWS website for the Springfield (Missouri) Weather Forecast 

Office (WFO). Between July 1, 2005, when storm–based (or polygon) warnings were first being tested in 

Springfield, and May 25, 2011, the NWS issued 18 tornado warnings for all or some part of Joplin. Only 

4 of these 18 NWS tornado warnings (shown as blue polygons in Fig. 4–3) were followed by verified 

tornadoes. This yielded a false–alarm rate for the Joplin area of 0.78, or 78 percent (14 false alarms out 

of 18 warnings). This rate is similar to the long–term average false–alarm rate for the Springfield WFO 

(0.774). For the era of storm-based warning 2007 to 2011, the national average false–alarm rate was 

0.747, or 74.7 percent. 

© OpenStreetMap contributors. 

Enhancements by NIST. 

Joplin 

Figure 4–3. The polygons associated with the 18 tornado warnings issued by the NWS 

between July 1, 2005, and May 25, 2011 (false alarms shown in red, warnings followed by 

verified tornadoes shown in blue). 

During the 5 years preceding May 22, 2011, the NWS issued 12 storm–based tornado warnings for Joplin. 

These warnings were issued on the following nine dates: June 8, 2007; March 31, 2008; May 10, 2008; 

May 24, 2008; June 4, 2008; April 9, 2009; June 9, 2009 (three warnings that day); June 3, 2010; 

September 16, 2010; and May 12, 2011. Of these 12 warnings, only 1 (May 10, 2008) was verified as an 

actual storm event. Therefore, over the most recent 5–year time period, the false–alarm rate for NWS 

warnings for Joplin was 0.917 (about 92 percent of warnings were false alarms). 

It is also important to determine the number of times per year that the sirens sounded in Joplin. Counting 

the weekly tests, except for instances when the weather was already bad, the test sirens sounded 

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Chapter 4 

approximately 52 times per year. Also, according to the Joplin–Jasper County emergency manager, the 

average has been once per year (at most) since 2007.137 In 2007, the sirens sounded once in Joplin for 

severe thunderstorm winds in excess of 70 mph (on January 18, 2007). The next year, the sirens sounded 

for an EF–1 tornado that hit outside the Joplin city limits (on May 10, 2008). Then, in 2009, the sirens 

sounded on May 8 due to winds in excess of 85 mph. The next time the sirens sounded, according to the 

emergency manager, was on May 22, 2011. Therefore, it can be concluded that the emergency manager 

for Joplin was not sounding the sirens for every tornado warning issued by the NWS for all or some part 

of Joplin, but rather was making siren–activation decisions based on other factors as well. Also, the 

emergency manager did sound the sirens for the one warning that was verified in the Joplin area (prior to 

May 22, 2011) since 2007. In the meantime, sirens were tested on a weekly basis, each Monday morning 

at 10 a.m., sounding for 1 min each time. 

An understanding of the false–alarm rate, the history of siren soundings, and the history of tornadoes is 

important because it can provide insight into public behavior in response to tornadoes. Because sirens 

and tornado warnings often do not convey the severity of the storm, large numbers of false alarms (even 

for weak storms) can lead to public complacency (Wang and Kapucu 2008). Residents and visitors in the 

Joplin area who received NWS–issued tornado warnings were exposed to false alarms 92 percent of the 

time, based on the most recent 5 year period. Additionally, although tornadoes had occurred in and 

around the Joplin area, the City of Joplin had only experienced the strength of EF–2 (or F–2) or lesser 

storms before May 22, 2011. 

4.4 JOPLIN, MISSOURI, ON MAY 22, 2011—THE TORNADO HITS 

This section of the report tells the story of the public response to and the consequences resulting from the 

deadly tornado that hit Joplin, Missouri, on Sunday, May 22, 2011. Even though the NWS SPC in 

Norman, Oklahoma, began forecasting storms for the area up to 3 days prior, this account begins that 

Sunday morning and ends when the tornado left the Joplin city limits at approximately 5:50 p.m. that 

evening. In this section, we look to the survivors of the May 22, 2011, Joplin tornado, since they either 

experienced the event firsthand or have knowledge of the experiences of family members or friends who 

experienced this tragedy. 

The weather that Sunday morning was described as beautiful. As people woke up and began their day, 

the sky was blue, the sun was shining, and there were only a few clouds in the sky. It was, however, 

unusually hot and humid for May, described by one interviewee as a “summer day” in the spring (NIST 

Interview 102138). 

Joplin was bustling with residents and visitors attending to their Sunday activities at home or elsewhere. 

Places of worship were open, with some, like the Full Gospel Church and Harmony Heights Baptist 

Church, holding both morning and evening services. Local retailers open that Sunday included Dillon’s 

grocery, Home Depot, and both local Walmarts, among others. Restaurants and specialty food shops 

opened for the breakfast and lunch crowds, and expected greater–than–usual patronage in the afternoon 

following the Joplin High School graduation ceremony to be held at Missouri Southern State University 

137 Keith Stammer, emergency manager for Joplin/Jasper County, personal communication, 2013. 

138 See Section 4.2.1 of this report on information pertaining to NIST interview data and data collection methods. 

250 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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(MSSU). Hospital staff tended to patients at SJRMC, located in the southwestern part of Joplin (inside 

the path that the tornado would later take through the city), and at Freeman Hospital, located to the south 

of SJRMC (outside the path of the tornado).The emergency communications timeline (displayed in 

Chapter 2 as Fig. 2–6) shows that Joplin’s first official tornado–related emergency message on May 22, 

2011 was delivered at 1:30 p.m. However, people had been made aware of the possibility of storms on 

Sunday, via weather reports, as early as Friday, May 20, 2011. On Sunday afternoon, at 1:30 p.m., the 

SPC issued a tornado watch for a large area of northwest Arkansas, southeast Kansas, eastern Oklahoma, 

and southwest and central Missouri, which included Jasper County. Once a severe thunderstorm watch or 

warning or tornado watch or warning was issued for the Joplin area, EOC dispatchers notified all police 

officers on duty, the fire department, and emergency management officials. However, since an incident 

in 2008 when a volunteer spotter was killed in Newton County, the City of Joplin has not assigned spotter 

locations to police officers or other officials (and did not do so on May 22, 2011).139 Any police officers 

who provided information on the May 22, 2011, Joplin tornado were already on duty in certain areas 

inside and outside of the city. 

The SPC issued a “moderate” risk of severe storms for the area described above at 3 p.m. However, the 

weather in Joplin still did not provide much evidence of the possibility of afternoon storms. Some people 

noted the presence of clouds, even with the sun shining, but the only indication of something brewing that 

afternoon was the existence of slightly darker clouds in the sky to the west of Joplin. 

Residents at home spent the afternoon watching television programs or movies, eating or preparing 

dinner, doing chores, getting ready to leave (for work or church, for example), or sleeping. Some were 

monitoring the weather at this time, checking the radar via the Internet or switching back and forth 

between the Weather Channel and local weather or news sources. 

Other people were out and about throughout Joplin, pursuing their Sunday engagements. Some were 

working the afternoon or evening shifts at local Joplin restaurants, businesses, and hospitals. Others were 

completing their Sunday errands at local Joplin businesses or attending local religious services or study 

sessions. Additionally, the high school graduation ceremony was being held at MSSU, located in the 

northwestern part of Joplin. 

By 5 p.m., the weather had begun to change in Joplin. The sky became overcast and cloudy, and some of 

the people later interviewed by NIST (especially those who had been located farther to the west) 

described the conditions as stormy or rainy. One interviewee, who was outside at the time, noticed that 

conditions to the west “looked very strange—like sort of a yellowish–greenish color, which isn’t 

typical...” (NIST Interview 129). At 5:09 p.m., the NWS’s Springfield WFO issued a tornado warning 

(see Tornado Warning Polygon 30 in Chapter 2, Fig. 2–5) that focused on a storm cell affecting northeast 

Joplin, from which a tornado never resulted. The text of this warning message can be found in Appendix 

M. 

Individuals receiving this tornado warning were also made aware of the possibility of storms to the 

northwest of Joplin, specifically identified as heading toward Carl Junction, Missouri. The EAS was 

initiated with this tornado warning. Two minutes later, at 5:11 p.m., the 25–siren alert system was 

activated throughout the City of Joplin. As mentioned earlier, the sirens sounded for 3 min with a 

139 Keith Stammer, emergency manager for Joplin/Jasper County, personal communication, 2013. 

NIST NCSTAR 3, Joplin Tornado Investigation 251 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

continuous tone, and then stopped. The decision to activate the siren alert system was made based on 

conversations between emergency management officials of Cherokee County and Joplin–Jasper County, 

information from the NWS that they were going to issue a tornado warning for Jasper County (the 

warning that was disseminated at 5:09 p.m. for Tornado Warning Polygon 30, affecting northeast Joplin), 

the direction of travel of that tornado, and anecdotal information from a local emergency official (outside 

of Joplin) regarding the destruction being caused by that particular storm.140 

The NWS’s Springfield WFO issued another tornado warning at 5:17 p.m. This warning was issued for 

Tornado Warning Polygon 31 (see Chapter 2, Fig. 2–5), which included southwest Jasper County and the 

entire City of Joplin (the text of this message can also be found in Appendix M). The EAS was also 

initiated with this second NWS warning. Approximately 21 min later, and as the tornado entered the 

Joplin city limits (at 5:38 p.m.), Joplin’s 25–siren system was sounded a second time. Even though the 

Joplin–Jasper County emergency procedures did not specify the use of a second tone, the decision to 

sound the sirens a second time was made based upon discussions between Joplin–Jasper County 

Emergency Management (EM) and the Joplin Fire Department regarding an NWS statement on the size 

and intensity of the tornado in Tornado Warning Polygon 31.141 Shortly after the second siren sounding 

was initiated, KOKC radio (a local radio station in the Joplin area) called Joplin–Jasper County EM. As 

the EM office was answering the station’s question as to why the sirens were going off a second time, the 

telephone call cut out and the EM representative was unable to complete his explanation. It is suspected 

that the tornado had eliminated telephone communications. According to Joplin–Jasper County EM, this 

was the only time that they had direct communication with any media outlet before the tornado tore 

through Joplin. After the tornado hit, Joplin’s public information officer was stationed at the EOC for 

approximately 4 weeks, answering requests from media outlets and getting information out to the public. 

The 5:09 p.m. tornado warning for northeast Joplin, the 5:11 p.m. siren alert, and the subsequent 

emergency information delivered via these and other communication channels (including the tornado 

warning issued at 5:17 p.m. and the second siren alert activated at 5:38 p.m.) began a series of response 

behaviors in the Joplin area. The receipt of certain types of emergency information related to the tornado 

varied depending upon where individuals were located within the Joplin area, which in turn, influenced 

their perspectives on the storm and resulting response behaviors. Therefore, it is important to correlate 

the narratives of survival obtained by NIST with the narrators’ physical locations throughout the Joplin 

area between the times of 5:09 p.m., when the first set of emergency communications was delivered, and 

5:50 p.m., when the tornado left Joplin. 

The Missouri State Police Department provided to NIST a list of names and locations of the 161 

individuals who lost their lives due to the May 22, 2011, Joplin tornado.142 Table 4–1 provides 

information about where these victims were located during the tornado. 

The locations that are featured in the following sections are those where all but 3 of the 161 tornado– 

related fatalities143 occurred: the Elks Lodge where 4 people died, SJRMC where injuries sustained that 

day led to a total of 14 fatalities, the Stained Glass Theater where 3 perished, the Greenbriar Nursing 

140 Keith Stammer, emergency manager for Joplin/Jasper County, personal communication, 2011 and 2013. 141 Keith Stammer, emergency manager for Joplin/Jasper County, personal communication, 2013. 

142 Originally, 162 names were provided to NIST by the Missouri State Police; however, months after the tornado occurred, one of 

the names was removed for not being associated with the Joplin tornado. 

252 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Table 4–1. Distribution of fatalities based upon location of 

injury/deatha from the May 22, 2011, Joplin tornado listed in 

alphabetical order by location name. 

Locations of Injury/Deatha Number of Victims Percentage of Victims 

AT&T store 1 0.6 % 

Elks Lodge 4 2.5 % 

Full Gospel Church 4 2.5 % 

Golden Corral 1 0.6 % 

Greenbriar Nursing Home 19 11.8 % 

Harmony Heights Baptist Church 3 1.9 % 

Home Depot 8 5.0 % 

Meadows Healthcare facility 2 1.2 % 

Outside (12 in vehicles) 20 12.4 % 

Pizza Hut 5 3.1 % 

Residences: apartments 12 7.5 % 

Residences: homes (detached) 62 38.5 % 

Stained Glass Theater 3 1.9 % 

St. John’s Regional Medical Center 14 8.7 % 

Walmart 3 1.9 % 

Total 161 100.0 % 

a. Location where the victim was killed or sustained the injury that led to his or her death. 

Home where injuries led to a total of 19 deaths, places of worship (the Full Gospel Church and Harmony 

Heights Baptist Church) where a total of 7 died, the AT&T store where 1 life was lost, the Home Depot 

where 8 deaths occurred, the Pizza Hut that was the site of 5 deaths, Walmart store #59 where 3 lives 

were lost, private homes and apartments where 74 perished, and in vehicles and outside of structures 

where a total of 20 people died (see Fig. 4–4). The circumstances encountered at these locations by 

survivors and decedents are chronicled, and supplemented by stories from people who survived in other 

Joplin locations under similar circumstances. Quotes taken directly from survivors’ detailed accounts are 

used as support for findings and to provide additional detail where necessary. 

These narratives are also supported by the data collected on injuries. Table 4–2 identifies the location 

when injured of the 71 individuals from the CDC dataset whose data were used by NIST in relation to 

where the deaths occurred in Joplin, as well as the severity of their injuries. NIST considered that the 

143 The circumstances surrounding the remaining three deaths are discussed in Sec. 4.4.12, below. 

NIST NCSTAR 3, Joplin Tornado Investigation 253 
 

 

 

 

 

Chapter 4 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 4–4. Locations of the 161 fatalities resulting from the May 22, 2011, Joplin tornado.
 

Tornado estimated center track plotted in red.
 

254 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

Chapter 4 

Table 4–2. Distribution of injured persons based upon where injury 

was sustained, using CDC Epi-Aid Study data. 

Number of Injured Number of Severely Injured 

Location (from sample) (from sample) 

Locations Where Fatalities Occurred 

AT&T store 1 1 unknownb 

Elks Lodge – – 

Full Gospel Church 1 1 

Golden Corral – – 

Greenbriar Nursing Home 5 5 

Harmony Heights Baptist Church – – 

Home Depot – – 

Meadows Healthcare facility – – 

Vehicles (only) 18 8 

Pizza Hut – – 

Residences: apartments 3 1 

Residences: homes (detached) 32 18; 5 unknownb 

Stained Glass Theater 1 1 

St. John’s Regional Medical Center 5 1 unknownb 

Walmart 1 1 

Locations Where There Were Injuries but No Fatalities 

Payless Shoesource store 2 – 

7th Street Walmart 1 – 

Dillon’s Grocery store 1 – 

Total 71 35 (known) 

a. The injury data from the CDC Epi-Aid Study, described in Section 4.2.2, represents only a sample of 

the over 1,000 injuries resulting from this tornado. 

b. In a few locations, it was not possible from the available data to identify the severity of one or 

more injuries. 

NIST NCSTAR 3, Joplin Tornado Investigation 255 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

severely injured could have endured similar circumstances as those who died from injuries sustained in 

the tornado. With that in mind, a “severe” injury was categorized as one for which the person was 

hospitalized for eight or more days or admitted to a hospital ICU for any length of time.147 Additionally, 

to distinguish among the individuals categorized with “severe” injuries, the number of days that they 

spent in the ICU was also recorded. From the sample of 71 injuries, 49 percent were categorized as 

“severe,” 41 percent were categorized as “non–severe,” and 10 percent were of unknown severity. As 

stated earlier, NIST used these data only to support the findings presented on fatalities, rather than to 

derive any additional findings about injuries. 

4.4.1 Elks Lodge 

Located relatively close to the beginning of the tornado path in Joplin, at 1802 West 26th Street, Joplin 

Elks Lodge #501 contained a lounge where drinks were served, a restaurant, a billiard room, and a larger 

room where bingo was often held on Sunday afternoons.148 Five people were in the wood–frame building 

when the storm hit, and four of the five perished in the tornado (Stefanoni 2011). The building, which 

was subjected to an estimated maximum wind speed of approximately 170 mph, was destroyed by the 

tornado (Fig. 4–5).149 No interviews were collected by NIST or the CDC from the only survivor located 

in this building; however, NIST gathered media reports on the circumstances inside the lodge as well as 

information from an interviewee who was friends with one of the persons killed in the lodge. 

According to this interviewee (NIST Interview 82), and as corroborated by data from Red Cross 

interviews, one of the deceased walked into the Elks Lodge, yelling about the tornado as it was 

approaching the lodge. At that point, all five individuals inside the building started to run for the cooler; 

however, none of them made it inside the cooler in time. Four of the five died from impact–related 

injuries caused by multiple blunt–force trauma to their bodies, according to the death certificates. Reports 

on the casualties at the lodge note that the roof collapsed on top of the occupants (Kansas City Star 2011). 

One of the decedents worked at the lodge as a bartender. The one individual who survived was sheltered 

by her husband, who laid his body over hers when the storm hit the building. She sustained serious 

injuries. 

4.4.2 St. John’s Regional Medical Center 

SJRMC was also located toward the beginning of the tornado’s path through the city. The facility 

consisted of two complexes with eight different buildings (see Chapter 3, Fig. 3–6). The north complex 

comprised five buildings: the West Tower (building #1 on Fig. 3–6); the East (Patient) Tower (building 

#2); the Emergency Generator building (building #3); the Chiller Plant (building #4); and the Oncology 

Clinic building (building #5). The south complex included three buildings: Medical Office Building 

(MOB) 1 (building #6 on Fig. 3–6); MOB 2 (building #7); and the Physicians Office Building (building 

#8). See Chapter 3 for information on the design and construction of these facilities. The focus of this 

section is the behavior of the building occupants in both patient towers—the West Tower (seven–story 

building) and the East Tower (nine–story building)—before and during the May 22, 2011, Joplin tornado. 

147 David Sugerman, Medical Officer in the Division of Injury Response of the CDC, personal communication, 2012.
 

148 Elks USA, “Local Lodges Online” (www.elks.org/lodges/lodgefacilities.cfm?LodgeNumber=0501).
 149 Unless noted otherwise, the average maximum wind speeds cited in this chapter were estimated by NIST based upon the wind
 

field model described in Chapter 2. 

256 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

In the event of severe weather, hospital emergency procedures in the East and West Towers called for a 

two–phase approach (NIST Interview 7). The first phase, called “Prepare for Condition Gray,” was 

activated when there were storms in the area or there was the potential for storms. “Prepare for Condition 

Gray” was intended to prompt hospital staff to perform preparatory actions, such as closing the drapes 

and blinds to protect people from glass breakage, and informing patients and visitors that they should stay 

away from windows and other glass around the hospital. The second phase of the emergency procedures 

was referred to as “Execute Condition Gray.” Activation of this phase meant that there was severe 

© 2011 Courtney Flatt/KBIA. Used with Permission. 

Figure 4–5. Joplin Elks Lodge #501 destroyed by the May 22, 2011, Joplin tornado. 

weather in the area and there was the potential for a storm to hit the hospital. In this stage, patients were 

moved from their rooms into the hallways. If they were ambulatory and able, they moved to chairs 

already placed in the hallways. If they were unable to move themselves, their bed was moved to the 

hallway, with the head of the bed raised (and the back of the raised portion of the bed facing the 

windows) to provide additional protection from flying debris. Pillows and blankets were also used for 

protection. 

NIST collected narratives from medical staff, patients, or visitors on all floors of the hospital, except the 

fourth floor (i.e., a total of 10 individuals who had been on either the east or west side of each floor). In 

addition, information was collected from the hospital’s risk manager and the head nurse on duty 

responsible for the activation of the hospital’s emergency procedures. According to the risk manager, 

hospital “staff had kind of been on the alert all afternoon that there certainly was potential for severe 

weather” (NIST Interview 7). However, instead of being notified of the tornado warning from the 

hospital switchboard, which was the procedure in place, the head nurse received information about the 

tornado warning by hearing the outdoor sirens from her office inside the hospital. What she heard was 

likely the second round of sirens, activated at 5:38 p.m., since she only remembered hearing sirens one 

time and noted having only 5 min to 7 min between the time she heard the sirens and the time when the 

NIST NCSTAR 3, Joplin Tornado Investigation 257 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

tornado hit the hospital (NWS User/Business Interview 8150). When she heard the sirens, she told hospital 

security to Execute Condition Gray, which was announced over the hospital’s public address system. 

No other narratives collected by NIST, including those obtained from hospital staff, patients, and visitors, 

mentioned hearing the sirens from inside the buildings. Interviewees did, however, mention hearing and 

responding to the Execute Condition Gray announcement. Doctors, nurses, and staff began protecting 

patients and themselves by moving individuals from their rooms into the internal hallways on each floor 

(CDC Injury Interview 13A151). A patient located on the east side of the hospital on the sixth floor, for 

example, had just received word from her doctor that she was being released: 

The alarm went off. And she just stopped, and I said, “What are they 

telling us?” Cause it was a different sound than I had heard. She said 

they’re telling us that there’s a tornado. She said, “We aren’t going 

anywhere . . .,” so when they rolled me out into the hall and parked me 

there. (NIST Interview 53) 

But not everyone inside the hospital recalls hearing the Execute Condition Gray message. A couple had 

been waiting in the first–floor Emergency Room waiting area for 4 hours, when they recall that the 

hospital staff “finally got us down into an examining room” (NIST Interview 2). The couple was aware 

of the fact that Joplin was experiencing some bad weather, mainly rain and winds, but had no idea that a 

tornado was heading their way. Shortly after they were placed in the examination room, the husband felt 

his ears pop, which prompted him to shelter his wife underneath the examination room sink/cabinet 

fixture. Then, they heard a sound like a freight train (NIST Interview 2). 

When the tornado hit the towers, the buildings were exposed to approximate maximum wind speeds of 

170 mph. On the third floor (east), a visitor, her brother, and her father were located in the interior 

hallway when she heard the sound of the hallway door blowing open as the tornado hit. She looked down 

the hallway, witnessing everything from the west end of the hospital flying into the east end, where they 

were taking refuge: 

There were medical equipment, x–rays, chairs, etc., flying towards us. 

All we thought about was covering dad and protecting him. My brother 

put himself in front and over dad, I was over his back side and a nurse 

was covering the side of him. The wind was tremendous at that point. 

The next thing I remember is trying to not fly out of the window and 

thinking this can’t last much longer, they always say it is over in j ust a 

few minutes. Then a door from the room hit me in the back and made 

me fall to the ground. (NIST Interview 105) 

A woman in the hallway on the sixth floor (east) recalls being “pelted ferociously in the head with 

baseball size hailstones, broken glass, insulation, and tons of debris.” She and her husband, a patient in 

the hospital, protected themselves, as much as possible, with ceiling tiles and other flying debris that they 

could hold over their heads until the storm was over (NIST Interview 106). 

150 See Section 4.2.1 of this report on information pertaining to NWS interview data and data collection methods. 

151 See Section 4.2.2 of this report on information pertaining to CDC data and data collection methods. 

258 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

© 2011 Curtis Lynn Geise. Used with Permission. 

Chapter 4 

After the tornado passed and the winds subsided, the conditions inside the hospital made it obvious that 

evacuation was necessary (NIST Interview 6). Many of the patients had been hurt badly (NIST Interview 

106). The floors had been so damaged, and individuals so injured, that hospital staff realized they needed 

to find other locations in which to provide medical care (NIST Interview 7). A doctor described the 

conditions on the sixth floor of the West Tower in the following way: 

Walls in, doors in, door frames in, debris everywhere. You can’t 

imagine the shattering that goes on when you have materials exposed to 

that kind of wind. Plus just the wires that were down from the ceiling, 

all the equipment that’s inside a room, debris a foot, two feet deep some 

places that you had to move before you could get somebody out . . . but 

instantly without any thought you knew you were leaving this place 

because it was just absolutely wrecked. (NIST Interview 6) 

When the couple in the first–floor Emergency Room made it out of their examination room, they noticed 

the rain just pouring in from where the ceiling used to be. With water at their ankles, and live wires 

sparking around them, they were concerned about being electrocuted if they remained in the building for 

much longer (NIST Interview 2). See Fig. 4–6 for an example of damage done to the interior of the 

SJRMC. 

Figure 4–6. Damage to the 

interior of SJRMC. 

Prior to May 22, 2011, when an evacuation was considered necessary, the administrative supervisor 

normally would have made the decision and announced it using the overhead building–wide public 

address system (NIST Interview 7). However, this system was not available for use due to a full loss of 

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Chapter 4 

power throughout the hospital (see Chapter 3 for information on this loss of power). Additionally, debris 

and other building damage made it difficult to move through the buildings and verbally announce 

decisions to evacuate (or not). Therefore, it is speculated that many of the hospital staff quickly realized 

that the towers could no longer provide proper medical care for the patients, and thus, would have to be 

evacuated (NIST Interview 7). At this point, the only option available for evacuation was vertical 

evacuation via the towers’ four stairwells, since the elevators were non–operational (NIST Interview 7). 

A doctor on the sixth floor noted that he and his staff decided on their own to evacuate their floor, while 

another hospital staff member on the second floor noted that she and her colleagues were told by a 

firefighter walking through the building to evacuate their floor (NIST Interview 18). 

Some staff members had more difficulty than others evacuating their floors. The psychiatric ward, for 

example, had mainly ambulatory patients who could evacuate easily. The cardiac and neurological floor, 

on the other hand, had patients who could not walk, so it was difficult for them to evacuate (NIST 

Interview 6). The operating room, located on the second floor, took 3 hours to 5 hours to evacuate 

because many of the patients were not ambulatory (NIST Interview 18). Staff first helped those who 

could walk down the stairs and out of the building. The occupants used flashlights, cell phones, and 

lighters while going down the stairwells because they were very dark and full of debris. All staff 

members are supposed to carry flashlights; however, not everyone had one at the time of the tornado. On 

the neurological floor (sixth floor of the East Tower), they used the medical tool that is normally used to 

check patients’ pupils to provide light for navigating down the stairs. 

Also on the neurological floor, for the first 30 min after the tornado, the staff tried to get people out from 

under the rubble (NIST Interview 6). Patients stuck under water pipes were rescued first to prevent the 

possibility of hypothermia. After 45 min, a firefighter and other people from the community came to the 

floor to help evacuate the injured. This floor was the last to evacuate because a majority of the patients 

were mobility impaired and could not walk. 

Hospital staff used whatever they could find to carry the injured patients down the stairs and out of the 

hospital. The neurological floor used wheelchairs to bring the patients down the stairs. Four uninjured 

staff or members of the community would carry the injured person in the wheelchair down the stairs. 

There were a few patients on the sixth floor who weighed over 300 pounds. It was very difficult for the 

four people to carry and maneuver those patients down in the wheelchairs. Emergency medical 

technicians also brought in backboards with plastic handles to carry people out. However, one doctor 

mentioned his dislike for these boards because they were very flexible and hurt his hands when carrying 

patients down the stairs. Some patients were carried down on doors that had blown off of hinges. Med 

Sleds® were also used to transport patients down stairways, although not in the way they were intended 

to be used (NIST Interview 7). Med Sleds® are designed to allow two people to easily slide a patient 

down stairs. Once the patient is safely out of the building, the sled can be slid back up the stairs. 

However, the staircase must be clear. Because there was debris all over the stairs and it was also so dark, 

it was difficult to steer the sleds down the stairs and four people had to carry the patient on these devices 

during the SJRMC evacuation. 

After evacuating the hospital, patients were taken by bus, pick–up truck, or other types of vehicles to local 

hospitals. When the hospitals within and around Joplin became full, patients were taken to other hospitals 

located throughout Missouri, as well as Kansas and Oklahoma. 

260 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

A total of 14 deaths was attributed to SJRMC as a result of the May 22, 2011 Joplin tornado. Five 

individuals died on May 22, 2011, due to impact–related causes, i.e., multiple blunt–force trauma to the 

body, according to the death certificates. Of these five, all of whom were patients, four were located in 

critical care (or intensive care) units on the third or seventh floors of the hospital, and the other was 

located on the third floor, but not in intensive care (NIST Interview 7). In a media interview of a nurse 

working on the seventh floor of the hospital during the storm, she recalled seeing hospital staff standing 

over patients who were originally on mechanical ventilators and bagging them (manually ventilating 

them) after the storm had hit the hospital.152 Seven of the deaths attributed to SJRMC were of people 

injured at the hospital due to multiple blunt–force trauma to the body and who died days, weeks, or 

months later in other hospitals, according to the death certificates. Finally, two individuals suffered heart 

attacks in the storm at SJRMC and died either days or weeks later in other hospitals. It has been 

confirmed that at least one of these two individuals was a patient at the hospital before the storm hit. 

4.4.3 Stained Glass Theater 

The Stained Glass Theater was a playhouse located in Joplin at 1318 West 26th Street, very close to 

SJRMC. Late in the afternoon of May 22, 2011, the cast and crew had just finished a performance of “I 

Remember Mama.” As the cast was taking a curtain call, around 5:11 p.m., the first set of outdoor sirens 

sounded. These could be heard from inside of the theater. There were 56 people in the building when the 

tornado hit. NIST spoke with five individuals who were there, and one family member of a person who 

died at the theater that day. 

At curtain call, the theater’s director walked on stage to let the audience, cast, and crew know that there 

were sirens sounding in the City of Joplin. In an interview, an audience member tried to recall the 

director’s statement in the director’s own words: 

“The tornado is northwest of us and looks like it’s heading northeast.” 

Then she went on to say, “Now, the sirens are going on,” and at that 

point, yeah, we could hear the sirens. That was—again, as far as I know 

that was the first siren. The—she said that, “We have a strong building 

here and anyone who wants to stay is welcome to do so. We can all go 

down in the basement.” (NIST Interview 121) 

According to another interviewee, most of the patrons decided to leave (NIST Interview 120). One 

couple in particular thought about it for a short while, and then based upon the information the director 

provided as to the direction of the storm and the location of their house, they calculated that the tornado 

would likely miss the theater and their house, and they would much rather be home than anywhere else 

(NIST Interview 121). 

Since this had been the final performance of this play, many of the cast and crew decided to stay and help 

take apart the set (NIST Interview 120). One couple who worked concessions that day was among those 

who stayed (NIST Interview 115). They rationalized this decision with the knowledge that the tornado 

was located to the north of them (and they were located in the southern part of Joplin), and the fact that 

they were located in a sturdy building. They mentioned that the average tornado that they had witnessed 

152 YouTube video, “Nurse kept patients safe during tornado” (www.youtube.com/watch?v=74YFLjcVfxk&feature=relmfu). 

NIST NCSTAR 3, Joplin Tornado Investigation 261 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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prior to May 22, 2011, would never have damaged the theater building. Instead, they were used to a 

tornado hitting “a building or two . . . three or four or something, but no major damage like this one” 

(NIST Interview 115). An actor in the play also admitted that “I didn’t put much stock in that siren, 

because I’d heard them before, and 9 times out of 10, you hear the sirens but nothing really happens” 

(NIST Interview 120). 

Approximately 25 min after the first announcement, the theater director delivered a second message to 

those remaining in the theater. She announced that there was bad weather and “we want you to get to the 

basement right now” (NIST Interview 115). The basement stairs were approximately one–person wide, 

and not everyone made it down the stairs before the theater was hit by the tornado:153 

They weren't rushing and pushing to get down those stairs. People were 

very nice, just getting over there in line and going down the stairs as 

quickly as they could. But there just wasn't time to get that amount of 

people down. (NIST Interview 115) 

A couple who did not make it to the basement in time, and thus suffered injuries from the storm, threw 

themselves on the floor of the theater, in between theater row seats, which were bolted to the floor. Their 

recollection of the seats was that they “just bent over enough that it—I think it kind of sheltered us 

from—we got the wind and everything, but I think it sheltered us from being taken out” (NIST Interview 

115). The couple mentioned getting pummeled by debris over and over again: “just going across my head 

and back and everything from razor blades just cutting me. You know? And just felt awful, and I just 

didn't like—I didn't think anyone could make it through this” (NIST Interview 115). Eventually, 

something hit her husband in the head, rendering him unconscious for a while. Another interviewee 

survived in the lobby bathroom of the building (NIST Interview 120), located in the northeast corner of 

the theater building (the corner opposite from where the storm hit). He survived the storm “huddled up in 

a fetal position on the floor in the restroom,” mentioning that the storm never lifted him up into the air, 

but instead pushed him down into the ground as it passed overhead. 

The theater, an unreinforced masonry building with brick facade, was exposed to maximum wind speeds 

of approximately 170 mph from the tornado. Three theater occupants lost their lives due to injuries 

sustained from the tornado. The director, who was standing at the top of the basement stairs when the 

building was hit, was fatally injured that day (NIST Interview 115). According to the death certificate, 

the director died one week later in the hospital. The other two deaths occurred during the storm, caused 

by multiple blunt–force trauma to the body, according to the death certificates. According to 

interviewees, neither of these victims made it to the basement before the tornado hit (NIST Interview 

115). Six others were seriously injured at the theater; however, it is not known where they were located 

within the building when they were injured. 

There were no NWRs or televisions inside the theater building. It is unclear whether the theater had a 

radio, nor is it clear how the director and others were obtaining information about what was going on with 

the weather. One interviewee mentioned checking the weather on his iPhone before the performance 

153 In NIST Interview 115, it was reported that approximately 15 people made it into the basement before the building was hit. NIST 

was unable to obtain information about how many people were located in the building when the tornado hit; but it should be noted 

that there were individuals who, while they did not make it into the basement, survived inside the building. 

262 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

began, but did not mention using this to obtain information after the sirens sounded (NIST Interview 

120). 

The Stained Glass Theater was not the only building in Joplin that had access to an underground 

basement area. The Macadoodles wine shop, located at 3105 East 17th Street, contained an underground 

wine cellar that patrons and staff used to shelter from the May 22, 2011, Joplin tornado. Two 

Macadoodles staff members were interviewed by NIST and provided the following information about 

how they received word of the storm and where they took shelter (NIST Interviews 17, 131). 

Prior to May 22, Macadoodles management had decided that the wine cellar would be the safest place to 

go in the event of a tornado. Six customers (including a baby) and six managers and employees were in 

the store at the time of the May 22, 2011, Joplin tornado. Five minutes after the tornado sirens sounded 

for the second time, the lights started flickering and the occupants were discussing how the wind was 

picking up and it was getting dark outside. Someone from outside of the store entered and told the 

occupants that “the other side of town had been hit and it was heading straight toward us” (NIST 

Interview 17). Additionally, the manager of the store, looking out the front windows, could no longer see 

the cars parked in front, since it was raining so hard. It was at that moment that the manager, with help 

from other employees, led the six customers downstairs and into the wine cellar. As soon as everyone got 

downstairs, the power went out completely, and a flashlight was used to move everyone underneath the 

basement staircase: 

We were all hunkered together down. And one of the guys had a little 

boy who was going to be like a year old the following week, so he was 

down on the floor with the baby and we were all around him. You know, 

I mean we had kind of our arms around each other like that. You know, 

part of it was because we didn’t know how bad it was going to be and we 

just wanted to make sure we were holding together to protect that baby. 

(NIST Interview 17) 

No injuries or fatalities occurred in the Macadoodles that day, even though the wood–frame building, 

with wood roof trusses, was demolished by the storm. The building was exposed to maximum wind 

speeds of approximately 150 mph. 

The wine cellar was a big, 1,000 ft2 basement–like structure, encased in concrete, approximately 20 ft 

deep (NIST Interview 131). It was accessed via a large oak stairway. The cellar was open during 

business hours so that customers could shop for the high–priced wines kept at cooler, cellar–level 

temperatures. It was an open area, in that customers could see into the wine cellar from the first floor. 

Macadoodles did have a television in the store, which was tuned into the weather reports that afternoon, 

as well as a radio playing overhead, from which one of the interviewees recalled hearing EAS tones two 

different times. 

4.4.4 Greenbriar Nursing Home 

The Greenbriar Nursing Home was located only a few blocks east of the Stained Glass Theater, at 2502 

South Moffet Avenue in Joplin. The Greenbriar, an unreinforced masonry building with wood roof 

trusses, was one of six nursing facilities within the City of Joplin. The nursing home suffered a direct hit 

NIST NCSTAR 3, Joplin Tornado Investigation 263 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Chapter 4 

from the tornado on May 22, 2011 (Tetz 2011), and was exposed to an estimated maximum wind speed of 

approximately 170 mph. NIST attempted to interview individuals who had been located in the nursing 

home before and during the storm, including management personnel, but was unable to do so. The 

information discussed in this section was obtained from media accounts and from CDC interviews of five 

individuals who were injured in the facility during the storm, conducted by the CDC as part of its EPI– 

Aid study (see Sec. 4.2.2 for more about the CDC study and dataset). 

A total of 19 fatalities from the May 22, 2011, Joplin tornado are attributed to the Greenbriar Nursing 

Home, which was completely demolished by the tornado (see Fig. 4–7). All deaths were due to impact– 

related causes, except for one individual whose cause of death was pneumonia (and whose death occurred 

one month after the tornado hit), according to the death certificates. Five of the 19 fatalities were 

individuals who were injured at Greenbriar Nursing Home and later transported to hospitals where they 

died from their tornado injuries, according to the death certificates. No information was found on the 

exact cause of death for these five fatalities; only the cause of the injury that contributed to their death 

which was recorded on the death certificate. There was a media report that the cause of at least one of 

these five deaths was mucormycosis, a fungal infection that attacks the body after injury (Younker 

2011a); however, NIST was not able to independently confirm that report. 

Figure 4–7. The small brick wall in the foreground (to the left of the van) is one of the few 

portions of the Greenbriar Nursing Home left standing following the May 22, 2011, Joplin 

tornado. (The building standing in the background was not part of the Greenbriar.) 

According to media accounts (Tetz 2011), 85 residents were located in the nursing home when the 

tornado hit, assisted by 10 nursing home staff members. The facility’s emergency procedures for 

tornadoes called for the staff to move residents to inner hallways and to close all doors to residents’ rooms 

to block out flying glass (Younker 2011a). 

It is not known how the residents and staff received word about the tornado, or whether everyone took 

refuge inside the building. One of the reported refuge locations was the nursing home’s central hallway. 

CDC interviews indicated that the staff placed as many residents as possible in the central hallway. 

According to media reports and CDC interviews, people located in this hallway became buried in rubble 

when the tornado hit. The ceiling, including pipes, plaster, wood, and whatever else was located above, 

264 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

came crashing down upon them. Additionally, where sections of the roof were blown off by the tornado, 

people were lifted out of the building and sent flying by the storm’s strong winds (Younker 2011a). It is 

unclear whether people were lifted from the central hallway or from other locations throughout the 

nursing home. Another location in which people reportedly took refuge was a small closet inside the 

nursing home (Younker 2011a). 

4.4.5 Places of Worship 

Although several places of worship were located within the tornado’s damage path, there were two such 

places where fatalities occurred: Harmony Heights Baptist Church, located at 2025 Indiana Avenue in 

Joplin, and the Full Gospel Church, located at 1828 Michigan Avenue (also in Joplin, one block northeast 

of Harmony Heights Baptist Church) (see Fig. 4–8). 

0 0.5 1 1.5 2

Miles

Full Gospel 

Church

Harmony Heights 

Baptist Church Joplin Heights 

Baptist Church

Joplin Missouri 

Stake Center

Spirit of 

Christ MCC

0 0.5 1 1.5 2

Miles

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 4–8. Locations of places of worship, denoted by black plus signs (+) where 

people died and yellow circles where there were no fatalities, along the tornado damage 

path (red line marks the estimated center line of the path). 

NIST spoke with two individuals who attended evening services at Harmony Heights Baptist Church on 

May 22, 2011, and collected additional data from media accounts and Red Cross interviews. The evening 

service had begun at 5 p.m. and the pastor was getting ready to preach when the congregation154 heard the 

sirens sound outside. Although the first set of sirens prompted some discussion among attendees as to 

what was going on and what to do, the second set coincided with talk about tornadoes heard on the fire– 

department radios of off–duty firefighters who were attending the service (NIST Interview 22). The 

pastor then prompted people to go to a safe place, because the radio discussions had sounded serious 

(NIST Interview 22). Some attendees took shelter in the church library, while others went to the church 

nursery. Individuals in the library laid down on the floor and waited for the tornado to pass. 

The Harmony Heights church building, which was a combination concrete masonry unit and wood–frame 

structure with wood roof trusses, was exposed to maximum wind speeds of approximately 160 mph. 

154 The number of people present at Harmony Heights Baptist Church on May 22, 2011 (before the tornado hit) has not been 

confirmed by NIST, although a media account cites 53 people (Word&Way 2012). 

NIST NCSTAR 3, Joplin Tornado Investigation 265 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Three women died in this building during the May 22, 2011, Joplin tornado, all from impact–related 

injuries. One woman was crushed to death in the children’s nursery area, laying over her son (who 

survived). Another woman was killed as she stood in the doorway of the nursery. An interviewee noted 

that the woman killed in the doorway was unable to shelter on the floor due to knee injuries. Another 

woman was pelted by debris and fatally injured as she laid on the floor of the church library (NIST 

Interview 22; Word&Way 2012). 

The Full Gospel Church lost four of its parishioners in the tornado. This church, which occupied a wood– 

frame building, was exposed to an estimated maximum wind speed of 150 mph. Information on the 

circumstances at the church during the storm was obtained from media accounts, Red Cross interviews, 

and CDC interviews. No survivors from the Full Gospel Church were interviewed by NIST, and 

therefore, no information was gathered by NIST on how parishioners were made aware of the impending 

tornado. Information was acquired only on where the deceased were located at the time of death and the 

circumstances of their deaths. 

As the storm approached the church, the 30–member congregation huddled and sang together in the 

church nursery (Babb 2011). When the tornado struck, the roof of the church flew away (Babb 2011), 

causing the walls of the structure to collapse onto the occupants. Four parishioners died that evening 

inside the nursery; two survivors specifically noted that the cause of these deaths was collapsing walls.155 

However, not all of the occupants took refuge in the nursery. One individual interviewed as part of the 

CDC EPI–Aid Study noted that he or she heard the sirens before walking into the church, got scared and 

immediately took refuge in the church bathroom.156 As the tornado hit, this person was thrown from the 

bathroom along with a toilet stall, and he or she was subsequently hospitalized for more than 2 weeks due 

to blunt–force trauma and lacerations. 

All deaths at Harmony Heights Baptist Church and Full Gospel Church were due to impact–related 

injuries (i.e., multiple blunt–force trauma to the body), according to the death certificates. Additionally, 

all of these individuals died on May 22, 2011. 

NIST interviewed individuals who had been in other places of worship located throughout the tornado 

damage path. Patrons of the Joplin Heights Baptist Church, located at 2107 Willard Avenue in Joplin 

(almost completely outside of the tornado’s damage path), took refuge in the interior hallway. An 

interviewee was prompted to look outside by the first round of sirens, which he dismissed, since there was 

“nothing odd about the sky yet” (NIST Interview 37). Walking around outside to study the clouds a bit 

later, he heard the sound of a freight train and immediately knew that a tornado was coming. He did not 

hear the second set of sirens, nor did he have a cell phone with him to check for information about the 

weather. At this point, approximately 15 individuals got into the hallway of the church building. The 

building (construction type unknown) sustained no damage after being exposed to maximum wind speeds 

of approximately 80 mph. There were no fatalities attributed to the storm at Joplin Heights Baptist 

Church, and the interviewee suffered no injuries as a result of the tornado. According to the interviewee, 

the church building was composed of concrete block, and suffered very little damage from the storm 

(NIST Interview 37). 

155 This information was gathered via Red Cross interviews documented on American Red Cross Disaster Health Services Mortality 

Report Forms. 156 The location of the bathroom inside the Full Gospel Church is unknown. 

266 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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The Joplin Missouri Stake Center, located one block south of Harmony Heights Baptist Church on the 

tornado’s estimated center line/track (at 2100 Indiana Avenue in Joplin), suffered a much higher level of 

damage (NIST Interview 73). This church, a wood–frame building with concrete masonry unit exterior 

walls, was hosting a meeting for single adults at the time of the tornado. When the sirens sounded (which 

the authors speculate had to be the second set of sirens), an interviewee looked to a weather application 

on his mobile device that showed a storm directly over the top of Joplin. He went to find the seven others 

in the building, and they all took refuge in the small women’s restroom, “just off the baptismal font, 

which had no windows and four solid walls” (NIST Interview 73). He stated that, “having lived in 

Missouri for almost 30 years, I had experienced this routine before and was thoroughly expecting the 

storm to be another one that did no damage, and just passed us by, so I did not panic” (NIST Interview 

73). As soon as everyone took refuge, he could hear the roar of the tornado as it approached. All eight 

laid down on the floor of the bathroom, when they 

felt the roof lift off over our heads and forces lifting us skyward. 

Everyone’s hair began standing on end and my suit coat jacket began 

billowing upward and is seemed that a giant vacuum cleaner had its 

sights set on lifting us out into the stormy sky. Someone reached out and 

grabbed my tie to keep me from being sucked out. After a few seconds, 

the vicious sucking was not as severe, but the winds continued with fury 

. . . flying cinder blocks flew into the opening and smashed the porcelain 

sink and toilet just beyond where we lay on the floor. Miraculously most 

of the flying debris missed us completely except for a cinder block that 

struck a blow to the top of my head and a piece of flying metal cutting 

[another person]. The air was filled with insulation, shingles, dirt, sand, 

and wood splinters. (NIST Interview 73) 

Except for a few scrapes and bruises, there were no injuries among the eight people located in that 

bathroom during the storm. Most of the building around them had been destroyed, after being exposed to 

maximum wind speeds of approximately 170 mph. 

Parishioners participating in Bible study at the Spirit of Christ MCC, located at 2904 East 20th Street in 

Joplin (two blocks from the Macadoodles shop), had access to a basement for shelter during the storm 

(NIST Interview 63). The 10 attendees had just completed a study session when the sirens first sounded. 

They proceeded to check their mobile devices for weather information, and went outside to look for any 

environmental clues. They found nothing out of the ordinary. The weather information predicted some 

heavy thunderstorms but they saw nothing to worry about “except for a few clouds in the west.” So they 

went back inside to finish their studies (NIST Interview 63). The interviewee also noted that “the sirens 

stopped going off, which typically if something is going on, they just stay on” (NIST Interview 63). It 

was not until the sky looked as if it was turning green, the wind had picked up, and the sirens sounded a 

second time, that the pastor decided that they needed to get everyone to the basement. At that moment, 

the windows began “popping out” (NIST Interview 63). 

Only 8 of the 10 occupants made it into the basement before the storm hit; the other 2 suffered injuries. 

Both of the injured persons “dove into the floor in the bookstore where there was a couch. When [one] 

woke back up with the rain hitting his face, the couch was on the edge of the foundation with him hanging 

onto it. So they’d been pulled about 20 feet and yet, everything else [from the building] was gone” (NIST 

Interview 63). Both injured men had been hit in the head, and one of the two was knocked unconscious 

for some time before being woken up by the rain (NIST Interview 63). The Spirit of Christ MCC, a 

NIST NCSTAR 3, Joplin Tornado Investigation 267 
 

 

 

 

 

 

 

 

 

Chapter 4 

wood–frame structure, was exposed to an estimated maximum wind speed of approximately 170 mph. 

No one was killed in this building from tornado–related injuries. 

4.4.6 AT&T Store 

One individual died the evening of May 22, 2011 at the AT&T store, a building constructed of metal– 

frame walls with brick facades, located at 1702 South Range Line Road in Joplin. NIST sought 

information from media accounts on the events that occurred inside the store. NIST’s attempts to contact 

the AT&T company were unsuccessful. 

Media reports stated that five employees were inside the AT&T store on the afternoon of Sunday, May 

22, 2011, and that they were closing the store before the tornado hit (CWA 2011). According to these 

reports, the employees could hear tornado sirens from inside the store, and the first set of sirens prompted 

them to lock the store doors (Skinner 2011). The doors had been locked for 15 min when a family of six 

pulled up to the store. At that point, one of the employees noted that there was debris in the air. 

Employees unlocked the store doors and allowed the family (two adults and four children) inside. 

Everyone (five employees and the family of six) rushed into the men’s bathroom located at the back of 

the store (Skinner 2011; CWA 2011). One of the employees tried to lock the bathroom door, but was 

unable to do so (Skinner 2011), and the tornado hit. They could hear glass breaking, likely from the 

storefront (Skinner 2011). As they huddled together, they began to hear what sounded like walls crashing 

down (see Fig. 4–9). 

© 2011 David Campbell. Used with Permission. 

Figure 4–9. The AT&T store following the May 22, 2011, Joplin tornado. 

268 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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The store was exposed to an estimated maximum wind speed of approximately 160 mph during the storm. 

One employee remembered the bathroom door coming off the hinges, slamming him in the back, and 

sending him flying into a brick wall (CWA 2011). Another employee recalled feeling for a moment like 

he was flying and then the sensation of being crushed, before he was knocked unconscious. When the 

storm was over, building materials and other debris had pinned some of the employees, so much so that 

they were unable to move. Those who could free themselves went for help, and those who remained 

realized that there was one death among them (i.e., an employee). One employee stated that the deceased 

was pinned down by a metal door (Skinner 2011). The severity of injuries to survivors at the AT&T store 

is unknown. 

The AT&T store was not the only commercial structure in which patrons and employees took refuge in 

locations toward the back of the store. Two blocks south of the AT&T store, patrons and employees took 

refuge in the back of a yogurt shop called Cherry Berry (located at 1900 Range Line Road in Joplin), 

which was a wood–frame building. An employee was interviewed about her experiences inside the store 

before and during the May 22, 2011, Joplin tornado. She and the other occupants were first made aware 

of the weather by the sound of the tornado sirens. After thinking about what the sirens meant to her, she 

provided the following explanation: 

We’re in kind of a valley, and most tornadoes will hit surrounding areas 

but it’s a rare occurrence where one will ever hit Joplin. And they sound 

the tornado sirens all the time. Every spring we hear ‘em go off at some 

storm, and people around this area go on their front porch and sit there 

and wait for something to come. I mean nobody really takes shelter. 

And so the tornado sirens didn’t faze anybody. Nobody in the building 

was worried. (NIST Interview 123) 

It was not until another employee received a phone call informing him or her that a tornado was located at 

17th Street and Michigan Avenue in Joplin that people started to take notice. At this point, the manager 

at Cherry Berry decided to get everyone into the bathrooms located in the back of the yogurt shop. They 

placed as many people in the bathrooms as possible, and others (three employees) were sent to the back 

offices. Before she took refuge in the offices, the employee who spoke to NIST recalled moving to the 

front of the store to get a view of the weather. She recalled “seeing debris flying all around us and I 

remember the windows shaking, and then I saw a car go flying in the air” (NIST Interview 123), and that 

prompted all three employees to run to the back offices. The three employees and one patron rode out the 

storm in a back office. 

They knew that the tornado was upon them when they felt their ears popping. The interviewee recalled 

the destruction created by the tornado: 

We were on the north wall, and I was sitting against the door which was 

on the east wall. So I’m sitting northeast in there trying to hold the door 

shut, and then all of a sudden the whole building starts vibrating in that 

door. And we have that 2,000–pound—we have eight, 2,000–pound 

yogurt mixers in there, and so all of a sudden the door is just bashing me 

and him up against that wall, ‘cause I can’t keep it shut all by myself. 

And [fellow employee] finally scoots over towards me and he puts—he 

shields his—he shields me with his body, basically. He tucked my head 

underneath his armpit, kind of had me in a choke hold, and he said for 

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Chapter 4 

me to hold on as tight as I can. And then the south wall ended up getting 

sucked out, and so there was a pretty good chunk of the south wall that 

went missing, and so I don’t remember as much as the sound as I do that 

door banging the most and then when the eye of it came I thought it was 

done. And I don’t remember dialing my phone, but apparently I tried to 

call like 10 people in the eye of it and I ended up connecting to my mom, 

and I told her the wall’s been sucked out, we’re buried under rubble, I 

think it’s done, and then I remember saying it’s not done, it’s coming 

again. And I remember her saying on the phone oh my God I’m coming 

to get you. And I remember me yelling, do not come up here, you will 

get killed, do not come up here. And then I hung up the phone and we 

braced for the end of it. We braced for the other part of the tornado to 

come through and about at that time we could feel the suction of the 

tornado, ‘cause we were missing a pretty good chunk of the wall and all 

of a sudden the ceiling came down on us. A huge chunk of ceiling, 

heavy, and it landed right on top of our heads, and that’s probably the 

only thing that kept us from getting completely sucked out. And then 

finally after it stopped for the most part, we sat there for a second just to 

make sure. (NIST Interview 123) 

She recalled having concrete embedded in her shirt and that her scalp was bloodied due to the debris that 

had pummeled their bodies. There were no deaths inside the Cherry Berry, which was exposed to an 

estimated maximum wind speed of approximately 170 mph. The employee whom NIST interviewed did 

not have to seek medical attention, but recalled scrapes and bruises, and being completely covered in 

fiberglass that was painful to scrub away. 

4.4.7 Home Depot 

The Home Depot store located at 3110 East 20th Street in Joplin was another location within the 

tornado’s damage path where people lost their lives on May 22, 2011 (see Fig. 4–10). It was a one–story, 

box–type system building, and further information on its construction can be found in Chapter 3. 

Information from death certificates, corroborated by information from other sources (see Sec. 4.2), 

indicated that eight individuals died at this Home Depot during the storm. However, a NIST interview 

with one of the store managers located in the store that evening found that seven individuals, including 

one Home Depot associate, died inside the store that evening. NIST received information from Home 

Depot’s corporate offices about the store’s tornado emergency procedures. The CDC EPI–Aid Study did 

not include any individuals injured inside the Home Depot by the tornado. All information reflected here 

on the circumstances encountered inside the Home Depot before the tornado hit was obtained from media 

accounts (Younker 2011b) and NIST interviews. 

Prior to May 22, 2011, the Home Depot had standard operating procedures for tornado emergencies 

(NIST Interview 149). The procedures stated that once managers became aware of an imminent tornado 

emergency, they were to monitor broadcasts for information about the developing storm. If an official 

warning was issued for an area in which a Home Depot store was located, management would notify 

customers and associates via the building–wide public address system to remain calm and move into a 

nearby aisle. Associates would then direct customers to the appropriate refuge areas in the store. 

Depending upon the particular Home Depot location, refuge locations could include any of the following: 

the restrooms, break room, training room, or office areas located in the rear of the store. These locations 

270 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

were chosen as refuge areas because they were separated from the selling floor; i.e., these areas contained 

no products or windows, and thus were not subject to threats from projectiles, and were located near an 

emergency exit. Once inside the refuge area(s), people were to be told to cover their heads and crouch 

down until the storm threat ended. 

Figure 4–10. A view of the Home Depot building that collapsed in the May 22, 2011,
 

Joplin tornado.
 

Interviews with the acting store manager on duty during the May 22, 2011, Joplin tornado provided 

information on how individuals in this Home Depot received word of the storm (NIST Interview 152). 

The managers had been monitoring the weather since earlier in the day via the Internet (i.e., the 

computers at the service desk), weather applications on smart phones, regular radios inside the store, and 

the store’s NWR. When the first sirens sounded, which the store manager could hear from inside the 

store, department managers made announcements to customers via the public address system. These 

announcements were to the effect that store occupants should be aware that bad weather was approaching, 

store management was not yet sure how serious the situation was, but to remain alert for further 

information. From this point, the store manager continually monitored all of the previously identified 

channels of information. Additionally, he called family and other managers and assistant managers 

(outside the store) to see if anyone had access to a live television feed on the weather. The store manager 

also monitored the weather by watching the sky outside of the Home Depot. When he saw power lines 

flashing off toward the west side of town, he decided that it was time to warn customers and staff to take 

shelter. This was because, to him, the power flashes (i.e., seeing blue and green flashes in the sky, rather 

than the yellow or white flashes typically made by lighting) meant that there were power lines going 

down and damage was occurring somewhere. At that point, the store manager made a store–wide public 

address announcement stating that store associates should direct all customers to the training room 

immediately and that this was not a drill. Shortly after that, according to the manager, the second sirens 

sounded. Approximately 30 people had gathered in the training room for only a short time (no specific 

amount of time was reported) when the tornado struck the building (NIST Interview 149). 

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Chapter 4 

The Home Depot was exposed to an estimated maximum wind speed of approximately 170 mph. The 

concrete wall at the back of the store collapsed outward (i.e., away from the people located in the training 

room) under the force of the tornado’s winds (see Chapter 3 for additional information about the damage 

to the building). The steel stud and plywood wall of the training room, which separated the room from 

the rest of the store, toppled over into the training room and rested on top of one of the tables inside the 

room, leaving a 3 ft “crawl space” available to the occupants. People who had taken refuge inside the 

training room were able to crawl out of the wreckage nearly unharmed (NIST Interview 152). 

Seven or eight individuals (depending upon the source) located inside the store that evening did not 

survive the storm. According to the store manager’s interview with NIST, these individuals had entered 

the store through the lumber entrance minutes to seconds before the storm hit the Home Depot. After 

entering, these individuals turned left and were walking parallel to the store’s front wall, when a section 

of the wall slab fell inward (into the store) and landed on top of them (NIST Interview 152). One of the 

individuals who died in the Home Depot that evening was a Home Depot associate (Turner Report blog 

2011) who had gone to the lumber entrance to unlock the door and let in two groups of people as the 

storm was approaching. The death certificates of the eight individuals attributed (by death certificates) to 

the Home Depot noted that they died the night of May 22, 2011, from blunt–force trauma to the body. 

4.4.8 Pizza Hut 

People were dining and working in the Pizza Hut located at 1901 South Range Line Road in Joplin during 

the afternoon of May 22, 2011. NIST conducted two interviews with employees of the Pizza Hut who 

were there during the storm and obtained additional information from an NWS interview with one of the 

two restaurant shift leaders on duty that day (NWS User/Business Interview 7) and media accounts 

(KSHB 2011; NBCActionNews 2011; Younker 2011c). Around 5 p.m., the shift leader noticed that the 

sky was getting dark and felt that something was different with the weather. Knowing that there were 

thunderstorm warnings out for the area, but unaware of the tornado watch, he called home only to find out 

that there was a tornado around the Galena area (approximately 7 miles west of Joplin, city center to city 

center). This information and the fact that delivery drivers were calling in regarding reports of hail storms 

in the area, persuaded the shift leader to wait inside the restaurant until the weather improved (note: his 

shift ended at 5 p.m.). 

Around 5:11 p.m., he heard the sirens first sound. At that point, he and other staff instructed customers to 

leave the store or take shelter inside the building, which he was required to secure (according to store 

policy). Three customers left the restaurant and approximately 14 customers remained (NIST Interview 

150). He also instructed staff to turn on the radio, which prompted others to check weather radar via their 

smart phones. According to interviewees, the store protocol advises patrons of the Pizza Hut to take 

shelter inside the cooler, which was insulated in foam and surrounded in sheet metal (NIST Interviews 

150, 151; NWS User/Business Interview 7). 

Around 5:38 p.m., the occupants heard the sirens sound a second time. Some of the patrons and 

employees discussed whether this was meant to signify an “all–clear message.” The interviewed shift 

leader did not believe the second sirens signified an all–clear message because the radio had not indicated 

that the weather had cleared. Therefore, he advised them to remain sheltered in the building. Shortly 

after, one of his staff noted that a tornado was located on Main Street, based upon radar information that 

he or she had accessed via a smart phone (NWS User/Business Interview 7). 

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Chapter 4 

After the second sounding of the sirens, management advised staff and patrons to take shelter or remain 

sheltered inside the cooler. Some individuals waited until they saw the storm approaching before entering 

the cooler. An employee grabbed the bungee cord that is normally used to pull the cooler door shut from 

the inside when employees enter or exit the cooler, wrapped it around his wrist, and tied it to a rack (NIST 

Interviews 150, 151). As the tornado ripped through the wood–frame restaurant, with an estimated 

maximum wind speed of approximately 170 mph, the cooler door slipped open. The scene was described 

by people inside the cooler in the following way: “And then when everything blew away, he was gone, 

the door was gone, everything” (KSHB 2011). 

The tornado killed five people at the Pizza Hut, including two employees, one of whom had tried to hold 

the cooler door closed with the bungee cord. The two employees were thrown from the cooler by the 

storm, one as far as 400 ft away to a nearby Aldi’s store, and the other into the Sonic store next door. The 

other six employees survived, but sustained injuries from being thrown as well. There were three 

confirmed fatalities among the customers. All five of the decedents died from multiple blunt–force 

trauma to the body inflicted by the tornado, according to the death certificates. 

A cooler was also used as a refuge from the tornado at the Dillon’s grocery store located at 1402 East 

20th Street in Joplin, which was in the center of the tornado’s path and one block east of Harmony 

Heights Baptist Church. NIST obtained information from store management and from two patrons 

present during the storm (NIST Interviews 132, 147). A manager at the Dillon’s store had been 

monitoring the weather conditions ever since the sirens first sounded. Equipped with information from 

radar (via the Weather Underground website) and his NWR, the manager made the final decision to 

shelter his employees and customers when the sirens sounded a second time and the weather radio noted a 

tornado warning. Additional confirmation was made when he noticed how windy it had become outside. 

He told everyone in the store, via intercom, that “we were under a tornado warning. And that if 

everybody would please go to my produce cooler” (NIST Interview 132). The cooler was made of foam 

walls with aluminum sheathing over the side. As the front windows of his store blew out, he was still 

shoving people back into the cooler, which eventually housed close to 35 people. He described what 

happened next: 

I pulled the two doors shut which were, they were just flimsy little bi– 

fold aluminum doors. The wind hit, and just literally ripped the doors 

out of my hands. And that’s when it really got nasty. I’m trying to hold 

the doors shut. It literally picked me up. It was pulling me out of the 

cooler. When two of the girls inside of the cooler grabbed hold of me 

and held onto me. And then it probably wasn’t, I’m guessing, 30 

seconds, maybe a minute, that it took for everything to [pause]—for the 

tornado to be over. It seemed like an hour, you know, because I sat there 

and I watched my store just literally disintegrate. We’re inside this little 

bitty cooler that’s probably 12–, maybe 15–feet wide, by 30–feet long. 

People are screaming. People are praying. Then it was over, you know. 

(NIST Interview 132) 

The Dillon’s store was a box–type construction made of CMU perimeter walls and open–joist steel roof 

trusses. The store was exposed to an estimated maximum wind speed of approximately 170 mph. See 

Fig. 4–11 for damage to the Dillon’s grocery inflicted by the May 22, 2011, Joplin tornado. The tornado 

caused injuries among building occupants, including cuts, bruises, and scratches; however, none of these 

injuries was life–threatening. 

NIST NCSTAR 3, Joplin Tornado Investigation 273 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

© 2011 Ellen Desmond. Used with Permission. 

Figure 4–11. Damage to Dillon’s grocery inflicted by the May 22, 2011, Joplin tornado. 

The cooler was located in a corner of the store, against the exterior wall on the western side of the 

building. After the tornado blew through the building, the cooler remained nominally intact. The cooler 

doors had popped off and a steel beam had fallen on top of the cooler, which crushed into the back part of 

it. However, when the tornado was over, the cooler remained standing. 

4.4.9 Walmart Store #59 

Walmart Store #59, located at 1501 South Range Line Road in Joplin, was another place within the 

tornado’s damage path where people lost their lives on May 22, 2011. Similar to the Home Depot, this 

Walmart store was a one–story, box–type system building; however, differences in the two buildings’ 

construction are noted in Chapter 3. NIST obtained narratives from three survivors who were in the 

Walmart store at the time of the storm, in addition to information from Walmart’s Emergency Operations 

Center (EOC) in Bentonville, Arkansas, regarding tornado procedures for the stores (NWS 2011). 

According to the Walmart EOC, when a tornado warning is issued for an area in which a Walmart store is 

located, a communications company contracted by Walmart (named Everbridge) calls and sends e–mail 

messages to the store’s managers to provide them with this warning information. The company bases its 

information on polygon warnings from the NWS. The store protocol for a tornado warning is known as 

Code Black, which is announced via the store public address system. When Code Black is activated, all 

customers and associates should proceed to the back of the building, in order to get everyone away from 

the front windows and doors as well as away from the over 200 skylights that are part of most Walmart 

buildings. Information provided by the Walmart EOC also states that the back of the store has more “real 

walls and restrooms.” It is up to the store manager’s discretion as to when (and whether) to cease store 

operations and instruct customers and associates to take shelter (NWS 2011). 

274 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

The manager at Store #59 had reviewed Walmart’s weather emergency procedures following the tornado 

outbreak that occurred in the Southeast United States in April, 2011. Also, on March 1 of every year, the 

Walmart EOC sends out preparedness information to all stores. 

On May 22, 2011, a telephone call and e–mail were received by the manager at Store #59 within 60 

seconds after the NWS issued the tornado warning (however, it is not clear whether this was the warning 

related to Tornado Warning Polygon 30 or 31). At the time, there were approximately 200 customers and 

associates inside the store (NWS 2011). An associate recalled that, shortly after the sirens sounded in 

Joplin (the first time), her manager walked around the store telling her and other associates that 

“everybody needs to leave and go back to Site to Store” (NIST Interview 99). Site to Store was an area in 

the back of the store where customers picked up merchandise ordered online. People slowly began 

moving to the back of the store as the managers continued to tell everyone, with urgency, to keep going to 

the Site–to–Store area at the back of the store (NIST Interview 99). Employees who had already gone to 

the Site–to–Store area were then told that if they left the area, they would be fired. Management said, 

according to an associate, “‘Do not leave this area. If you leave this area, you’re no longer Walmart’s 

responsibility.’ And so basically they were letting people know, ‘You must stay here. This is the safest 

area. You’ve got to stay here’” (NIST Interview 99). 

As this associate huddled with approximately 50 to 60 other people in the Site–to–Store area, she heard 

glass windows breaking and saw the two doors (fire escape doors) located nearby suddenly blow straight 

open. At that moment, the ceiling tiles lifted and the lights went out 

and we all jumped off the counter, landing all over each other . . . And 

we were just kinda this mass of arms and legs and bodies, and at that 

point, it was—you know, people were screaming and crying and cursing 

and praying, and I was praying . . . The girders broke all around us; they 

were like crashing down. Nobody really knew what was happening. It 

was just this horrible roar. I really didn’t know how long it lasted . . . 

And when it was over, there was a girder on my back, but it was 

resting—when I say “on my back,” it was touching my back, but it 

wasn’t laying on me. The girder had actually landed on one of the older 

men that could not get off the counter in time up above me, and it was at 

about a, oh, I wanna say a 45–degree angle. It was resting on the 

cabinet, and then it went down to a point inside the cabinets. It actually 

broke—well, the cabinets were pretty much destroyed on that end, but 

the weight of the girder, it crashed down. But that cabinet where that 

man was saved all of our lives in there, because it made like this—most 

of the girders, most of the ceiling girders, when they landed, they just 

made a cap and landed, mainly right across the cabinets. It made a little 

pocket inside of those cabinets; a little D–shaped pocket, where we had 

probably 50, maybe 60 people inside of there. (NIST Interview 99) 

Some injuries, although no exact number could be determined, did occur inside that “refuge” location. 

However, the associate was not aware of any fatalities that occurred within this Site–to–Store area of the 

store. 

A father and daughter took refuge in another location inside the Walmart. They were told by a manager 

to go to the back of the store. When people only leisurely took heed, the manager tried again, in a “pretty 

NIST NCSTAR 3, Joplin Tornado Investigation 275 
 

 

 

 

 

 

 

 

 

 

Chapter 4 

high tone of voice or something, by saying, ‘People, this is for your safety. Please move to the back of 

the store.’ And then I guess it dawned on people—they started moving a little faster. And then he said, 

‘Calm down. Take your time, just be safe—get back there’” (NIST Interview 81). The father and 

daughter made it as far back as the Electronics section of the store (directly in front of the Site–to–Store 

area) and waited there, when all of a sudden the lights flickered. The father remembers the ceiling tiles 

bouncing up and down, and when he heard the sound of the tornado, which sounded to them like a loud 

train, he told his daughter to get down. They both got down on their hands and knees and waited for the 

tornado to pass. When it was clear enough for them to raise their heads, the father saw what was an 

internal building column before the storm, now laying beside them. He also recalled that two people, 

located right beside his daughter and him, lost their lives that evening (NIST Interview 81). 

As discussed in Chapter 3, the uncollapsed north half of the building experienced a lower estimated 

maximum wind speed of 120 mph (EF–2 speeds, from a northerly direction) and the collapsed south half 

experienced a higher estimated maximum wind speed of 165 mph (EF–3 to EF–4 speeds, from a westnortherly wind direction) (see Fig. 4–12). A total of three people lost their lives that day in the Walmart. 

It is uncertain exactly where, inside the store, the fatally injured were located. However, information 

from the Walmart EOC notes that the fatalities were reportedly the persons closest to the center of the 

store. All three decedents died due to blunt–force trauma to the body, according to the death certificates. 

No information could be found on how many did not take shelter in the Site–to–Store refuge area or on 

the number of people injured at the store. 

N 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 4–12. Aerial photo of the tornado–damaged Walmart Store #59, showing the 

collapsed south half and uncollapsed north half of the building. 

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Chapter 4 

4.4.10 Single–Family Homes and Apartment Complexes 

The May 22, 2011, Joplin tornado damaged 7,411 residential buildings, including single–family homes157 

and at least five apartment complexes, along its path through the city. The five apartment complexes 

identified as having been within the damage path were the following: Connecticut Point apartments (2034 

Connecticut Avenue), Hampshire Terrace apartments (2020 Hampshire Terrace), Somerset apartments 

(2001 Connecticut Avenue), Dock apartments (2123 Rhode Island Avenue), and Plaza apartments (1715 

South Rex Avenue). 

Around 5 p.m. on Sunday, May 22, 2011, there were many people in the Joplin area who were located at 

home or at someone else’s home. NIST spoke to 109 individuals located at home when the storm hit, 99 

of whom were already located at home when they received warnings (or emergency information) after 

5:09 p.m., and 10 of whom were located elsewhere and then returned home after receiving emergency 

information. Figure 4–13 shows the locations of 104 of the 109 at–home survivors with whom NIST 

spoke directly. Each of these 104 locations (marking either a single–family home or an apartment) is 

indicated by a blue dot in Fig. 4–13. (Five of the 109 interviewees were not located on the map because 

their exact addresses were not provided to NIST.) Figure 4–13 also shows the distribution of the 

interviewees relative to the tornado’s estimated center track. It can be seen that some interviewees were 

located outside the damage path; they were interviewed in order to provide a more comprehensive story 

of public response to the emergency communication system (some of these individuals are also not 

plotted on Fig. 4–13). NIST also collected information on 34 individuals who were injured at home 

(using the CDC dataset) as well as on the 74 individuals who died in single–family homes or multi– 

family apartment buildings in Joplin. 

0 0.5 1 1.5 2

Miles

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 4–13. Geographic locations of 104 of the 109 NIST interviewees who were
 

located at home when the tornado hit Joplin. The red line indicates the estimated center
 

track of the tornado.
 

Very little information could be gleaned about how the deceased received information prior to the storm, 

except where NIST was able to speak with survivors who either spoke with these individuals or were 

located within the same home as they (the latter occurred in two single–family homes in this sample). 

157 The term single–family home is meant to identify all types of detached residential structures, which are distinguished here from 

multi–family apartment complexes or nursing homes. Single–family homes in this sample can include semi–detached homes in 

which two single–family homes share one “party” wall.

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Chapter 4 

CDC’s dataset of the injured did not contain information on tornado awareness. Therefore, general 

information on pre–tornado emergency communication within individual homes and apartments was 

gathered from the survivors who spoke directly with NIST, as well as from media accounts. Information 

on refuge locations (within homes) has been obtained for survivors (both NIST interviewees and injured 

persons from the CDC sample) and for those killed in homes and apartments (unless the deceased 

individual was home alone at the time of the tornado strike, making it almost impossible to obtain 

information on their refuge location). 

As mentioned earlier, the majority of the interviewees (99 of 109) were located at home at approximately 

5 p.m., when emergency information was provided to them regarding the storm, and they remained at 

home throughout the duration of the tornado event. However, it should be noted that only two of the 

interviewees mentioned that they were at home that Sunday specifically because they were fearful about 

the possibility of inclement weather. One of these two individuals, who was supposed to attend Joplin 

High School’s graduation ceremony at MSSU, relayed her reasons for remaining at home all day on 

Sunday: 

And I actually knew on Friday that we were supposed to have severe 

weather on Sunday. And I was actually supposed to go to the high 

school graduation that afternoon. My daughter’s oldest stepson was 

graduating, and I had a ticket to go . . . and I said if anyone wants my 

ticket, they can have it, because there’s supposed to be severe weather on 

Sunday and I’m not going anywhere. I was at home and it was a 

beautiful morning, but I just kept watching the weather because—I 

watched it on Saturday also, and they just kept talking about we were 

supposed to have severe weather on Sunday, with the possibility of 

tornadoes. And so I was just on top of it. (NIST Interview 110) 

All others were at home because that was their normal Sunday routine or what they had decided to do that 

Sunday, regardless of the weather. That is not to say, however, that these individuals did not monitor the 

weather while they were at home. While some were sleeping, getting ready to go somewhere, or 

watching movies, for example, and not monitoring the weather, others had turned to televisions, radios, or 

the Internet for weather updates, and even had these playing in the background while they engaged in 

other activities. 

Those interviewees already tuned in to news or weather stations received word of the tornado warning 

issued at 5:09 p.m. for Tornado Warning Polygon 30, the storm cell affecting northeast Joplin. 

Additionally, they and almost all others located at home heard the 5:11 p.m. outdoor sirens, even from 

inside their homes. An interviewee who lived in a heavily wooded area in Joplin, and an interviewee who 

was deaf, did not hear the sirens sounding. The same was true for the three interviewees who were 

sleeping when the sirens sounded and the warnings were issued. These individuals relied on telephone 

calls or text messages from other individuals to alert them of the warnings and impending storm. Only 

one interviewee was notified of the impending storm via a weather radio, even though many more 

mentioned having an NWR in the house. These latter interviewees admitted that their weather radio 

device was either not turned on, did not receive the signal, or did not go off (even though it should have) 

when storm warnings were assigned to their area. None of the interviewees mentioned receiving initial 

weather information via automated text alerts. 

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Chapter 4 

One response, implemented by only a few of those receiving this initial warning information, was to take 

refuge inside the home immediately. Only 8 of the 99 individuals who were already at home sought 

shelter immediately within their homes. Within this group, there were three individuals (3 of 99) who had 

already been highly concerned about the possibility of tornadoes on May 22, 2011 and had been 

monitoring weather information for most of the afternoon via television or weather–related websites (e.g., 

Intellicast or SkyWatch (local news)). They had begun and continued their search for information prior to 

the sirens sounding. The other five interviewees who took refuge immediately (5 of 99) after hearing the 

sirens explained that they always take such precautions: “I'm not somebody who stands on the porch to 

wait and see if I can see it when it comes. No, that's not me.” According to this interviewee, the sound of 

a siren means that a tornado is possible, and it could happen anywhere, any minute (NIST Interview 62). 

An action that was more commonly taken after hearing the outdoor sirens was to search for additional 

information to confirm the existence of a serious weather event. One option taken was to look at the 

conditions outside for confirmation. An interviewee who was watching a previously recorded television 

show noted that he 

used to live in Oklahoma, Oklahoma City specifically, so a lot of times 

when the sirens go off, my first thing is to look out the closest window 

that has the shades up. If I don’t see stuff flying in the air I know I’m not 

right in it. (NIST Interview 30) 

Another interviewee noted that “most of the time, you may glance outside and you may just wait for them 

[the sirens] to stop” (NIST Interview 85). For others, answers were sought by tuning into televisions or 

radios, especially to stations that regularly provide weather information. A response that was even more 

common than that was soliciting information and advice from family and friends about what was going 

on and what they should do about it. 

Unfortunately, very little information or cues were available at 5:11 p.m. for interviewees to use to 

confirm a threat. Interviewees noted that the weather looked “fine” outside (NIST Interview 92), looked 

like a storm was going to pass to the north (NIST Interview 11), or did not look threatening—just some 

light rain, thunder, and lightning (NIST Interview 31). A Joplin native who was expecting to see a 

tornado recalled that 

the neighbors were all out, looking around at the weather when this first 

siren went off, and they were just like me, wondering what's going on. 

Why is the siren going off when there's really nothing in the sky that 

looks like a tornado? (NIST Interview 42) 

Individuals who tuned into weather reports received news about a storm traveling to the north of Joplin, 

heading to Webb City, Missouri, or Carl Junction, Missouri (NIST Interview 43). A Joplin native 

remembered that 

the announcer and the weatherman that came on the TV seemed to say 

the track was, you know, mainly north of town. It wasn't going to be a 

bother for where I was at towards the south part of town. So, I continued 

to sit there on the front porch and enjoy the cool air that was, you know, 

for the day. (NIST Interview 58) 

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Chapter 4 

According to another interviewee, the storm “looked like it was even way up north, like Pittsburg. I said, 

‘That’s not gonna come down and get us.’ So I just kind of ate my food there and was watching that” 

(NIST Interview 94). The storm that weather forecasters were tracking at that point in time was a storm 

to the north of Joplin (Tornado Warning Polygon 30). After hearing this information and based upon the 

perceived tendency for storms to track to the northeast only, interviewees concluded that they were not at 

risk at the time of the initial siren/warnings. 

Conditions appeared similar to the 10 individuals NIST interviewed who were not at home when the 

initial warning and information about tornadoes were provided, but reached home before the tornado hit. 

These individuals were leaving Joplin High School’s graduation ceremonies, eating an early dinner at 

local restaurants, running errands at Joplin businesses, or attending worship services at around 5 p.m. that 

evening. Outdoor sirens were the primary way that these individuals were made aware of impending 

storms, after which they either looked to the sky, to televisions (i.e., in restaurants or shops), or to radios 

(in vehicles) for further information. None was afraid that an imminent tornado would hit them (or their 

house); they continued toward home because they were ready to get home anyway (regardless of the 

storm) or because they wanted to protect something (i.e., pets or their car) or someone (their children) in 

case a storm did occur. For example, a couple was located at a Joplin restaurant when they heard the 

sirens sounding: 

They had a TV monitor and a radio in the restaurant, and so we listened 

to that for a little bit. And at that particular time, they were talking about 

everything going to the north of us. So we went ahead and paid and 

decided to drive on home. (NIST Interview 44) 

Another couple was at the Joplin High School graduation when the sirens sounded. The husband 

recalled: “Look at the clouds. Look the sirens are going off. I said, ‘You know what? They do that a 

lot,’” and the couple continued home (NIST Interview 22b). Only one interviewee, who was heading in a 

northerly direction, driving to church, was concerned that he was actually driving into the storm. 

Therefore, he turned his car around and went back home (NIST Interview 101). Overall, individuals 

believed that it was safe to drive at that time, even after the sirens had sounded, since they did not see 

anything too threatening in the sky and/or they were aware that a storm was passing to the north, and they 

were traveling to the south of it. 

However, as those in vehicles continued home and others at home continued to monitor the weather, not 

much in the way of additional information was provided (either that the danger had passed (to the north) 

or that there was new and imminent danger from the west) before the second siren sounding. One 

interviewee decided to drive home from church with his children when the sirens sounded again because 

he was concerned about the level of safety provided by a “pre–fab building” (NIST Interview 54). He 

continued to monitor the storm via his vehicle’s radio: “I was listening to KZRG at the time. They said 

they didn’t indicate anything was on the ground at the time, but they issued this warning in advance 

because there was an area of circulation right about central—right about the State line—close between the 

State line and Central City Road. And so I thought, ‘Okay, I got time.’” (NIST Interview 54). Others at 

home recalled television statements about radar indicating that the storm was still to the north (NIST 

Interviews 11, 33, 102), that it looked like the storm was going to miss us since it was going around 

Galena (NIST Interview 23), that the storm had turned (NIST Interview 36), that the tornado hit a town in 

Kansas (NIST Interview 58), that there was a tornado on the ground in Galena (NIST Interview 85), and 

280 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

that there were severe thunderstorms to the west (NIST Interview 84). A few mentioned not seeing any 

warnings on television at all (e.g., NIST Interviews 118, 133). 

Even as late as 5:36 p.m., 2 min before the tornado entered Joplin city limits, television and radio stations 

were not confirming the presence of a large–scale tornado heading for Joplin. For example, KOAM–TV 

(Channel 7) and KFJX–TV (Fox 14) broadcast the following weather information between 5:36:48 p.m. 

and 5:38:19 p.m.158 : 

We are looking . . . oh . . . very close to downtown in Joplin, we have 

had confirmed funnels from westward from Galena to Riverton as it 

passes off towards the east at about 20, so it’s really working right 

through downtown and also the western side, so right in the heart of 

Joplin is where we are seeing the rotation and the confirmed reports of at 

least funnel clouds that can drop a tornado at any time and it’s going to 

continue to work off toward the east so eventually the east side of Joplin, 

you need to definitely watch this cell very closely, Dusquesne will be 

right in the track of this cell and continuing eventually to the 249 loop 

and then out near I–44. I think the heart or at least the rotation part of the 

cell will stay south of Carthage but the hail core’s going to really affect 

areas from Webb City to Oronogo, where you can pick up anywhere 

from golf–ball– upwards to baseball–sized hail. So again, right now we 

are watching this tornado warning, which is right through the Joplin 

metro, the heart, right around downtown moving east, and there’s 

numerous little areas of rotation, so I’m gonna go ahead and say from 

Duenweg back to the western side, you could see funnel clouds or drop a 

tornado so this whole area needs to take shelter as this could obviously 

be a very dangerous situation. Plus, on top of that the very gusty winds 

and the large hail. Of course, keep it here, I’m going to keep you 

updated . . . for now, back to programming. 

What prompted a majority of individuals located in single–family homes and apartments to take internal 

shelter from the storm, if they took shelter at all, was actually seeing, hearing, and feeling the effects of 

the tornado itself. One of the few interviewees tuned into an NWR recalled listening to the warning for 

Tornado Polygon 31 that put Joplin directly in the path of a tornado (NIST Interview 31). After receiving 

that information 

we didn’t stray too far from the front porch, and when we initially got to 

the front porch the second time the sun was out, although you could see 

off to the west and slightly to the north of where we lived that it was 

pretty dark and it was thundering and lightning pretty good; and then we 

had a little bit of hail. We did not seek shelter in the basement of our 

home until the trees in our neighbor’s yard came down, and we heard the 

sound, which I’ll never forget the sound—never, never, never—you 

never forget the sound. (NIST Interview 31) 

158 This text is a transcription from the television broadcast disseminated by KOAM–TV (Channel 7) and KFJX–TV (Fox 14) 

between 5:36:48 p.m. and 5:38:19 p.m on May 22, 2011. The video was provided to NIST by KOAM–TV. 

NIST NCSTAR 3, Joplin Tornado Investigation 281 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Some also credited the sound of the second sirens as a prompting mechanism for them, but for most 

interviewees, the second round of sirens sounded at the same time that they witnessed the tornado 

approaching. Interviewees painted a picture of the danger they saw, felt, and heard between 5:38 p.m., 

when the tornado entered Joplin, and 5:50 p.m. (approximately), when the tornado left the city. A young 

couple and their kids were playing in the house that day, when the father saw what could only be 

described as a black, thick wall of debris: 

We heard the tornado siren come on. So [my child] had kinda gotten 

away from my wife and was running around, kind of—he was trying to 

remain just being a kid. Then it was there. It was boom! You could 

hear it. It was now—the grinding noise in the background was front and 

center. You couldn't hear anything else. The sirens were almost 

drowned out, and it was coming upon us. I was able to look out our 

door, and I was able to see. It was just—it was moving fast . . . a wall of 

debris and I saw pieces of houses 100 foot off the ground. (NIST 

Interview 5) 

Another Joplin resident described it as a huge dark cloud, and “it was an animal like coming toward me, 

toward my door” (NIST Interview 14). People mentioned that the trees were swirling, swaying, and even 

laying down in a manner that they had never seen before (NIST Interview 111), and cars were lifted off of 

the ground (NIST Interview 22b). The visual cues were accompanied by the sound of the tornado, 

described most often as like that of a freight train or continual thunder. Also, interviewees mentioned 

feeling their ears popping as the tornado grew near. 

Interviewees also recalled multiple television channels that were broadcasting a visual shot of the tornado 

via their camera (i.e., Nexstar Broadcasting (parent company for KSNF–TV (NBC Channel 16) and 

KODE–TV (ABC Channel 12), KOAM–TV (Channel 7), and KFJX–TV (Fox 14)), allowing viewers to 

see firsthand the damage left in its path. A woman at home at the time heard the second siren and thought 

that it was odd to hear a second one sound: 

So I clicked on and I was watching a local TV station that has a tower 

cam that was facing the west. And they were watching some big black 

cloud that looked like it was coming across the State line. And they said 

they couldn’t tell if it was just the thunderstorm moving in or if there was 

something else. And then they started seeing—it wasn’t lightning. They 

were hitting transformers and it was like power lights, you know, like an 

explosion. I guess when it hit this transformer. (NIST Interview 133) 

Interviewees remembered the newscasters’ voices on a Nexstar channel sounding more alarmed than 

usual (NIST Interview 129). It was at this time that a female anchor decided to give instructions to the 

listening audience. Some interviewees even credited her specifically for their decision to take cover, 

mainly due to the things she said and how she said them: 

She was like, “Oh, my God.” She said, “Everybody, take cover. Take 

cover now.” She said, “It's coming right at us.” She said, “I mean now” 

in a very hysterical voice, and my husband and I looked at the TV at the 

same time, and we could see on the weather cam the wedge tornado, and 

she was just yelling, you know, “It's coming right at us.” (NIST 

Interview 84) 

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Chapter 4 

Even when the picture cut out, she pleaded with her listening audience, “If you can still hear my voice 

you need to take cover now.” And, at that moment, the power went off (NIST Interview 129). 

Interviewees began realizing that there was something really wrong, and that they needed to find shelter 

from the storm, if possible. The options available in single–family homes throughout the Joplin area were 

primarily internal (centrally located) bathrooms, closets, laundry rooms, or hallways. Basements were 

scarce, due to the consistency of the soil and the difficulty this soil posed for constructing basements in 

the Joplin area (as noted in Sec. 4.3.3), and there were only a few known locations where individuals had 

in–home storm or tornado shelters. Interviewees in apartment buildings took refuge in internal areas of 

their first–, second–, or third–floor apartments, or on the ground floors of their complexes (and in one 

known case, under a public staircase (NIST Interview 41)). 

Inside their shelters, individuals used pillows, couch cushions, blankets, and in a few cases,159 mattresses 

to keep debris from injuring themselves and their loved ones. Inside bathrooms, as many family members 

as possible took refuge in the tub, throwing pillows and blankets over the top for protection (NIST 

Interviews 23, 41, 114). Men sheltered women, couples held each other, parents covered and protected 

their children, whatever it took to keep their families and friends safe from the storm (NIST Interviews 

27, 40, 102). 

Interviewees in single–family homes rarely took refuge in their crawl spaces. Only one interviewee noted 

using his or her space for protection before the storm hit.160 Overwhelmingly, interviewees did not feel 

like they had enough time to access the crawl space. Additionally, interviewees admitted that the spaces 

were difficult to get into, and since many decided to take protection as the tornado was bearing down 

upon them, they considered the crawl space impractical (for example, Interviews 5, 29, 88, 90, 114). A 

Joplin native described this predicament in the following way: 

By the time I get to the other end of the house, go outside, pull off the 

roof, get underneath the house, go back inside, grab two dogs, take them 

back out there, put them under the house, go back inside and grab the last 

dog, I’m dead. We’re all going to die. (NIST Interview 88) 

Others were concerned that the crawl space was not large enough to provide access to them, their family 

members, and/or their pets (NIST Interview 101) or would prove difficult to get out of (due to pre– 

existing injuries) once the storm was over (NIST Interview 36). Finally, the conditions in crawl spaces 

were not always attractive, even in the face of an impending storm (NIST Interviews 32, 85). A woman 

reflected on the crawl space option, saying 

we did have a crawl space, but we didn't have—we thought about going 

under there. One, my daughter didn't wanna go under the house. She 

159 In one case, three men died and one man was severely injured after they took refuge under a mattress in the utility room of a 

single–family home. In two cases, survivors took mattresses into internal refuge areas within the home (NIST Interviews 52, 67). 

In one case, a family took refuge under a mattress in their bedroom, with the husband laying on top of the mattress (NIST 

Interview 77); and in another case, a survivor got in between his mattress and box spring to take shelter from the storm (NIST 

Interview 58). 160 This statistic does not include the one family that had access to a crawl space and did not use it because they had access to a 

storm shelter. The statistic does encompass eight couples, each located in a separate home, in which neither spouse chose to 

access the crawl space. It is not clear if these were joint or individual choices. 

NIST NCSTAR 3, Joplin Tornado Investigation 283 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

thought it would be too muggy and too scary under there. (NIST 

Interview 84) 

NIST spoke with a few individuals who did not take protective action or shelter before the storm hit (or 

knew of someone inside their home who did not take shelter). At one home, an elderly husband and wife 

who were both hard of hearing were unaware that a tornado was heading right for them. Just as the 

woman walked up to light a few candles near a window 

the glass window—doors—blew in and knocked me 18 foot across the 

room and into the hall. As I went through the hall door, the door frame 

and door fell down. All of a sudden, I realized—I quit flying, and I was 

laying in a puddle of water and glass. My husband started yelling, come 

help me. He had—the recliner he was sitting in had turned over, so he 

was pinned under the recliner and wood and sheetrock debris. (NIST 

Interview 118) 

In another instance, a husband decided against taking refuge with his wife and son (who protected 

themselves in the interior hallway), and instead, remained in his bedroom while the tornado ripped apart 

his home (NIST Interview 40). The husband died, while his wife and son survived, albeit with injuries. 

Some people were thrown from their houses, others lifted up in place, desperately holding on to pipes, 

appliances, and each other. A couple who was visiting family was sheltering in a bathroom with four 

other adults, when the tornado grabbed hold of the wife: 

And it just felt like somebody took and grabbed me by my waist and just 

jerked me back as hard as they could. And it just felt like we were 

flying, but actually we were going down to the ground, but it didn’t 

really have that sensation. It just felt like we were flying. And so, we 

kind of stopped. And then—and my husband—when my nephew threw 

the mattress in, he grabbed a hold of it and he was holding it in front of 

me and he was partially underneath it or behind it but not totally. So, 

whenever we stopped, walls started falling on us. And then we went 

again. It pulled us even more. And, again, it just felt like, you know, we 

were not really landing on the ground, but going backwards. (NIST 

Interview 52) 

The walls and roof that eventually caved in upon them were stopped by the hot water tank, which the 

couple credits for saving their lives. 

Other individuals were actually taken up into the air by the storm. A man who was sitting inside his 

bathroom, on top of the toilet, heard his house ripping apart around him. He recalled: “The next thing I 

knew I was jerked rather violently airborne. Swung out the house, or swung out into space somewhere. I 

remember a 360 in the air, next thing I was skidding across the yard and came to a stop” (NIST Interview 

11). Another interviewee also sheltering in his bathroom had hunkered down in the bathtub as the storm 

hit his house. He remembered the following: 

When I was sitting there in the bathtub the roof got ripped out that 

portion of the house, and I could feel my feet were getting pulled up in 

the air, and I was actually holding on to the bathtub faucet. My feet—I 

284 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

was kind of—pretty much—well I was at a 45–degree angle in the air for 

probably a good few seconds, and then some debris from I think my 

neighbor’s—pretty sure my neighbor’s house ended up falling on me and 

holding me back down. That’s probably the only point that I really—it 

really kind of made me feel that I was really in danger. (NIST Interview 

30) 

Interviewees suffered anywhere from no damage to their house to the entire house being scraped off of 

the foundation, with nothing left. Fig. 4–14 shows a foundation and ground floor, all that was left of a 

house located within the damage path, along with the occupant’s vehicle, which before the storm was in 

the garage. The winds even ripped some of the tiles and carpeting from the floor of this house. The 

occupant was sent flying into the storm as his house was ripped apart; however he did not suffer any life– 

threatening injuries. 

Figure 4–14. Demolished home located within the tornado 

damage path in Joplin. 

A total of 74 people died at home due to injuries sustained from the tornado; 62 individuals in single– 

family homes and 12 in multi–family apartment complexes. The locations of these deaths are displayed 

in Fig. 4–15. The 62 deaths in single–family homes included two individuals who suffered stress– 

induced heart attacks at home, and later died in a hospital. The homes of these two individuals were not 

damaged. The 62 deaths also included one individual whose final cause of death was pneumonia, from 

which he or she died 2 months after the storm hit. The death certificate for this person cited congestive 

heart failure and dementia as secondary causes of death. It is unclear whether stress or taking refuge from 

the tornado was the cause of this person’s fatal injury, since no damage occurred to the home. Finally, 14 

of the 62 deaths involved people who were injured in their homes due to impact–related causes, and then 

died later in hospitals (days, weeks, or months after May 22, 2011), according to their death certificates. 

NIST NCSTAR 3, Joplin Tornado Investigation 285 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

All 12 deaths that occurred in multi–family apartment complexes were caused by impact–related injuries 

and all but one of these deaths occurred during the storm, according to their death certificates. 

0 0.5 1 1.5 2

Miles

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 4–15. The geographic locations of deaths in homes and apartments in Joplin. 

Detached homes are designated by pentagon shapes and apartments by square shapes, 

with the red line indicating the estimated center track of the tornado. 

NIST focused a significant amount of effort to ascertain whether the fatally injured took refuge inside 

their homes, and if so, where they were sheltering when the storm hit. Twenty of the 62 persons who died 

from injuries sustained in single–family homes on May 22, 2011 had taken internal shelter (note: three 

sets of 2 people each and one set of 3 people were together in the same houses), 9 did not take shelter, and 

the sheltering actions of the 33 remaining decedents are unknown (note: three sets of 2 people each were 

together in the same homes). Many of these 33 are thought to have been alone or with someone else who 

died in the storm, making it difficult to find accurate information on their refuge locations when the storm 

hit their houses. Of the 12 people who died from injuries sustained in apartment buildings, 2 had taken 

shelter within their apartment (they were located together in a bathroom), 1 did not take shelter (he was 

sleeping in his room when the storm hit), and the refuge locations of the remaining 9 fatalities are 

unknown. 

Only 3 of the 62 persons fatally injured in single–family homes had access to a basement. These three 

individuals had access to partial basements, some portions of which were underground. Further research 

revealed that two of the three individuals did not go to their basements before the storm hit, and instead 

remained above ground (i.e., one was sleeping and the other remained sitting in his or her chair as the 

storm hit) (CBSNews 2011a, 2011b; NIST Interview 13; American Red Cross Disaster Health Services 

Mortality Report Form). As for the third fatally injured individual who had access to a basement, no 

information was found on whether he or she took refuge in the basement or remained above ground as the 

storm hit. 

NIST was also interested in the locations of injured individuals throughout the Joplin area. However, due 

to the sheer number of injuries, NIST was unable to obtain information on the location of each injury that 

occurred in single–family or multi–family homes. A total of 34 individuals were interviewed as part of 

the CDC EPI–Aid Study, all of whom spent some time in the hospital for their injuries. Looking only at 

286 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

the severely injured individuals within this sample, none of these 19 severely injured individuals had 

access to a full or partial basement within their homes or complexes.161 

4.4.11 In Vehicles or Outdoors 

Twenty fatalities occurred outside of structures on May 22, 2011. These were among individuals who 

were in transit, stopped in vehicles, or caught outdoors when the tornado struck. NIST spoke with 13 

survivors who were located inside their vehicles and 2 individuals who were located outdoors when the 

tornado struck. Fig. 4–16 shows the locations of these 15 survivors whom NIST interviewed. NIST also 

collected information on 18 individuals who were injured in vehicles (from the CDC dataset) as well as 

on the 20 individuals who died outside of structures (12 were located in vehicles and 8 were located 

outdoors). 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

0 0.5 1 1.5 2

Miles

Figure 4–16. Geographic locations of NIST interviewees located outside of structures 

when the storm hit (13 individuals were in vehicles and 2 were outdoors). The red
 

line represents the estimated center track of the tornado. Note: Two interviewees were 

located slightly beyond the boundaries of the aerial photograph; their locations are
 

shown to scale.
 

Very little information could be gleaned about those who were injured or killed in vehicles or outdoors 

related to how they received information prior to the storm, as NIST was not able to speak with any 

survivors who were with these persons before the storm hit. CDC’s dataset of the injured did not include 

information on tornado awareness. Information about the receipt of warning information by people who 

were in vehicles or outdoors during the storm was obtained from the 15 survivors who spoke directly with 

NIST, as well as from media accounts. Information on refuge locations within vehicles or outdoors was 

obtained for survivors (both NIST interviewees and the injured from the CDC sample) and fatalities. 

Persons who were already in their cars or who were located outdoors received initial alert/warning 

information via the 5:11 p.m. sirens and/or car radio–disseminated weather reports about the 5:09 p.m. 

161 Five of the 34 injured individuals had injuries the severity of which is unknown because not enough information was available on 

the injury. 

NIST NCSTAR 3, Joplin Tornado Investigation 287 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

tornado warning for the northeastern storm. Additionally, loved ones called to let individuals know that 

the tornado sirens were sounding or that the NWS had warned that a tornado was possible in northeastern 

areas of Joplin. There were also a few among this group who were initially located indoors (i.e., in public 

businesses throughout Joplin) and were made aware of the event by business staff. 

Similar to those in homes, no matter how these individuals received initial alert or warning information, 

very little information was available to confirm the existence of a threat for those located in what soon 

became the tornado’s damage path. People tuned into their car radios to hear that the storm was to the 

north, called or received calls from others and discussed the northern storm, or looked to the environment, 

which showed little of the tornado–related cues needed to prompt people to act. Additionally, the actions 

of others in the City of Joplin provided little in the way of threat confirmation. At 5:11 p.m., when sirens 

were heard at the Joplin High School graduation ceremony, for example, an interviewee noted that “the 

attitude of people that were outside was still very much in the festive, you know graduation day–type 

mode, taking pictures and hugs and you know that kind of thing. Didn’t see a lot of people like running 

for their cars or heading for shelter” (NIST Interview 15). 

Therefore, the individuals in vehicles or outdoors generally proceeded with their activities. These 

included continuing Sunday errands, traveling to work, or traveling to family dinners, especially to 

celebrate high school graduations. Some decided to travel to their next destination, as long as it was not 

located to the north (i.e., where storms were possible). Others decided that they wanted to go home, for 

example, to be with their spouse or to take care of their dogs; however, these decisions were based on a 

belief that they were not in any immediate danger and could safely continue driving around Joplin. 

As they continued on in their cars, many monitored the conditions and potential impending storm via their 

vehicle’s radio. However, depending upon the radio station that they listened to, they received different 

information about the weather. Interviewees recalled the following examples of information provided to 

them during this time period: 

	 There was a tornado in Carthage, Missouri (but nothing was said about a tornado on the ground in 

Joplin) (NIST Interview 26). 

	 There was bad weather in Kansas, and it was heading east (however, no specific locations were 

provided) (NIST Interview 28). 

	 There was a tornado warning (but with no specific information about any tornadoes on the 

ground) (NIST Interview 46). 

	 There was a tornado between Carl Junction, Missouri, and Webb City, Missouri (NIST Interview 

60). 

	 A tornado was spotted in Joplin at 7th Street and Schifferdecker Avenue, and then later, a tornado 

was spotted at the interviewee’s location (however, he did not experience the effects of a tornado 

at that particular location) (NIST Interview 66). 

	 The storm was moving to the northeast (NIST Interview 71). 

	 A tornado was hitting Carl Junction, Missouri (located northwest of Joplin) (NIST Interview 130). 

288 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

In some of these cases, interviewees were looking for specific information that a tornado had actually 

touched down before they were willing to take safety precautions, including stopping their cars. 

The two interviewees who were located outside when the storm hit were attempting to gain access to 

structures. One of them, who was caught outside of his home without his keys, was attempting to gain 

entry as the storm hit. He described the tornado approaching as he attempted to open the front door: 

I grabbed the storm door and opened it up, and I kicked the front door 

about half a dozen times like you see on the police shows. It didn’t 

budge. Didn’t move an inch. And so turned around and our neighbors 

had been out—the neighbors to the south of us had been out when we got 

home looking at the sky like everybody does around here. And I 

thought, well, we can run over there. Well, by the time I turned around 

and [headed] back to the edge of the porch, it was raining so hard you 

couldn’t see their house 20 feet away. So I ran back to the front door and 

about that time, over [girlfriend’s] shoulder—she had turned around and 

over her shoulder out in our front yard, a couple 8–foot lengths of 2 by 4 

landed in our front yard. And I—that kind of startled us and about that 

time the corner post that holds up the roof—the whole roof line goes 

down over the porch, too. And the corner post that holds it up over the 

edge of the porch just crumbled, just fell to pieces. The roof started 

coming down on us. (NIST Interview 28) 

The other outdoor interviewee was attempting to access a local grocery store when the tornado hit. Since 

the store had already locked its doors, the interviewee and her husband took refuge in the store’s alcove 

(i.e., right outside the front doors). Luckily, this store was not hit as hard as others, and remained intact 

throughout the storm. 

Of the 13 interviewees caught inside their vehicles as the storm moved through Joplin, 10 directly felt the 

effects of the tornado in some manner while in their vehicles. As the tornado moved closer and the debris 

wall grew thicker, these drivers were unable to see the road ahead of them, so they pulled their cars over, 

stopped, and hunkered down, hoping for the best. One mentioned that she had “seen a car a little bit in 

front of me blowing across the street” (NIST Interview 26). Another interviewee mentioned seeing the 

following conditions: 

Wind picking up and things flying through the air—small things—

nothing major. And then in between 17th and Range Line and 20th and 

Range Line is whenever I could see from the west it was very dark, and 

it’s like a wall of dirt, basically, and I guess it’s the outside stuff in the 

air finally got to the street or the road or whatever you want to call it. 

And that’s whenever—and it basically kind of just made it disappear, 

’cause it was so thick. And that’s whenever things started getting more 

serious, like in your head you’re running through your mind, “Okay, I 

probably don’t need to be here.” (NIST Interview 66) 

An analysis of the interviewees who were driving when the storm hit showed that all but one of them 

drove directly into the most dangerous parts of the tornado. (The remaining driver, who was sitting in her 

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Chapter 4 

car in a parking lot throughout the storm, was also located within the strongest portion of the tornado.) 

The rain–wrapped nature of the tornado (see Chapter 2), compounded by the presence of a significant 

number of structures, trees, and hills between the drivers and the tornado, and the large volume of dirt and 

debris surrounding the storm, were likely contributors to this behavior. A couple near 20th Street and 

Delaware Avenue recalled that “the sky had just went all black. You couldn’t see anything, and it was 

raining really hard” (NIST Interview 26). The notion of the tornado, from the driver’s perspective, not 

being “seen” clearly or at all was confirmed in a number of interviews, and corroborated through 

surveillance videos. An individual driving near West 32nd Street and Westberry Lane mentioned that he 

“could see a wall of water that was about 200 yards ahead of me and I just assumed that was the straight– 

line winds” (NIST Interview 15). Another interviewee at 20th Street and Rhode Island Avenue described 

the tornado as “a wall of clouds moving at me. It was still grey, but it was getting darker, and darker” 

(NIST Interview 60). After the clouds, he just started seeing a lot of debris. For these individuals, 

visibility was limited, probably to only 10 ft to 15 ft, causing many to pull over and wait out the storm 

that they were not certain was a tornado (NIST Interview 66). 

While interviewees who were located in vehicles recalled getting pummeled by debris (through broken 

windows), some even suffering severe injuries as a result, a van was picked up by the storm on Rhode 

Island Avenue, off of 20th Street in Joplin. An interviewee had turned onto Rhode Island Avenue, 

desperately trying to find someone, anyone, with whom he could take shelter. When he did not see 

anyone, he noted that he never felt more alone and empty, “because I just knew something bad was about 

to happen . . .” 

at that moment the windows exploded. I thought the windshield went 

out first, but actually seeing the photographs, it didn’t go anywhere. But 

everything else. The back window—side panel windows. They all just 

exploded. And that part I saw in slow motion. I saw the windows—

because see, a lot of people talked about feeling pressure and their ears 

pop. I didn’t feel that. My ears didn’t pop. My first indication was 

when the windows exploded—debris came flying through. I’m laying 

over in the seat. And was laying—I know I was laying there for, you 

know, a few seconds. I was laying there for ten, fifteen seconds. It’s 

always hard to gauge. But stuff’s flying over the top of me. 

Then it was like a giant hand picked me up. Didn’t pick me up. But it 

pulled me straight back to about where these red cars were, and 

everything and that. And I don’t know if I hit them. Because it felt like I 

bumped into something. But the minute I bumped into something, I went 

straight up. And I went. And I don’t really have a gauge how high I 

went up, except that I felt like I really lifted and went straight up. But 

now the thing is spinning the whole time. I’m spinning counterclockwise 

the whole time this is going on. Seconds. It was only seconds. But I 

saw debris flying around me. And I saw these things breaking apart. 

And about 30 or 40 seconds later, you couldn’t see. You couldn’t 

breathe. (NIST Interview 60) 

A total of 12 individuals located in 11 different vehicles died due to injuries sustained from the tornado. 

All 12 of these deaths were caused by impact–related injuries and occurred on May 22, 2011, according 

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Chapter 4 

to the death certificates. Due to the sheer number of injuries to individuals located in vehicles or 

outdoors, however, NIST was unable to collect or analyze information on each such injured individual. 

Among persons located outdoors during the storm, eight fatalities were attributed to the tornado. These 

fatalities included a police officer killed in the line of duty on Monday, May 23, due to a lightning strike. 

Also included in the eight deaths were the following: one individual located outside of SJRMC, who had 

been dropping someone off at the Emergency Room entrance; one individual located outside of the 

Greenbriar Nursing Home when the tornado hit; and three individuals who worked for Jasper Food 

Products and took refuge in a ditch.162 With the exception of the police officer, all fatalities that occurred 

outdoors were caused by impact–related injuries and happened on May 22, 2011, according to the death 

certificates. The locations of deaths in vehicles (indicated by red and blue highway signs) and outdoors 

(indicated by black diamonds) are shown in Fig. 4–17, in relation to the estimated center track of the 

tornado. 

0 0.5 1 1.5 2

Miles

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 4–17. The geographic locations of deaths that occurred in vehicles (indicated
 

by the red and blue highway signs) and outdoors (black diamonds) when the storm hit.
 

The red line is the estimated center track of the tornado. Note: Multiple deaths occurring
 

at the same location are represented by only one symbol.
 

It should be noted that a small subset of NIST interviewees were “in flux” during the storm; that is, they 

were in a vehicle at some point between their initial awareness of a possible tornado and the time when 

the tornado hit. Since they were not located at one of the places where deaths occurred, and they were not 

located inside a vehicle when the tornado hit, they were not included in the preceding portions of this 

chapter. These individuals began the event in one building, decided that it was safe enough to drive (or 

relocate) at some point before the storm hit, and ended the event (when the tornado hit) in another 

building. 

NIST spoke with two “in flux” interviewees who were located at home when the initial alert and warning 

information was provided, but then relocated to another building they perceived as safer in case a tornado 

hit. One individual took refuge nearby at the SJRMC (NIST Interview 80) and another sought protection 

in a convenience store located across the street from his or her apartment complex (NIST Interview 136). 

162 The cause of death listed on the death certificate for the three who took refuge in a ditch was not drowning, but rather blunt–force 

trauma to the body. 

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These responses constituted a small minority of the storm responses among NIST interviewees, who were 

more likely to stay at home (or return home) after receiving alert or warning information, rather than 

travel to another building. There were additional “in flux” individuals who received alert or warning 

information in one building (not their home) and then traveled to another building (continuing on with 

their errands). These individuals did not feel at risk during their travel, deciding that the storm was to 

their north and that as long as they kept to the south, they would be fine. The final group of individuals 

“in flux” during the storm included those who stopped to take refuge in a location to which they were not 

originally traveling. A woman in this group recalls her “close call” on 20th Street that evening: 

We was on 20th Street before we even knew there was gonna be a 

tornado. And so the wind and everything started picking up, we looked 

up in the sky, and there was the funnel. So when we got to 20th and 

Main, it just whipped our truck all over the place, and we had a hard time 

getting it to stop, and we was in the truck. And the windows and 

everything started breaking out, so we decided to go over to the store 

there on 20th and Main to try to go in for shelter. (NIST Interview 125) 

4.4.12 Additional Locations of Fatalities in Joplin 

An additional three fatalities, which were not discussed in the preceding sections, were attributed to the 

Meadows Healthcare facility (two deaths) and the Golden Corral restaurant. Meadows Healthcare was a 

nursing home located at 1805 West 32nd Street in Joplin. NIST did not speak with any individuals who 

had been inside this structure when the tornado hit. Additionally, the damage to this facility and the 

response of its residents and staff received very little media coverage. Two deaths occurred at this 

nursing home, and although both were caused by blunt–force trauma to the body, the death certificates 

also noted that at least one of these patients was suffering from cancer. Both deaths attributed to 

Meadows Healthcare occurred 2 days after May 22, 2011. 

One death was attributed to the Golden Corral restaurant, according to the death certificate. However, 

this attribution was likely made because the restaurant was the last place that anyone saw or heard from 

this individual. The conditions inside the Golden Corral are not analyzed in this report, since it is likely 

that this individual died in another location. 

4.5 CASUALTIES FROM THE MAY 22, 2011, JOPLIN TORNADO 

The May 22, 2011, Joplin tornado caused devastation throughout the city and beyond—destroying homes, 

businesses, churches, apartments, and other facilities, and leaving many injuries and deaths in its wake. 

This chapter has so far explored two main topics related to this devastation. Sec. 4.3 described conditions 

that existed in Joplin prior to the tornado and were relevant to how people responded to the storm on May 

22, 2011. These conditions included the emergency communications infrastructure, sheltering options, 

and prior exposure to tornadoes among the populace. Sec. 4.4 described how people responded to the 

impending threat of storms and to the tornado itself on May 22. This encompassed how people became 

aware of possible weather threats and of the tornado; where people were before and during the tornado, 

and why they were there; how these locations influenced people’s response options; whether, when, and 

how people sought to protect themselves and others; and the outcomes associated with these various 

locations, options, and behaviors. The present section focuses on the casualties (deaths and injuries) 

caused by the tornado, to provide insight into additional factors (beyond pre–existing community 

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Chapter 4 

conditions and individuals’ circumstances and behaviors on May 22) that may relate to how people were 

impacted by this storm. These factors include where and how people were killed and injured, when 

victims died, and the basic demographics (i.e., gender and age) of those killed or injured. 

The May 22, 2011, Joplin tornado produced the largest death toll for a single U.S. tornado since record– 

keeping began in 1950, taking the lives of 161 people at various locations throughout the city. In addition 

to the fatalities, there were many survivors who were injured in the storm. The City of Joplin attributed 

more than 1,000 injuries to the May 22, 2011, Joplin tornado.163 As indicated in Sec. 4.2, NIST was 

unable to obtain detailed information on each of the injuries attributed to the tornado, and consequently 

focused its analyses on the fatalities. However, some helpful information on injuries was gleaned and is 

presented here from both the larger ESSENCE dataset (of 876 individuals who visited emergency rooms 

in Missouri due to injuries from the tornado) and the smaller sample of 71 injured persons who were 

randomly selected from the ESSENCE dataset and studied by the CDC. These injury data provide 

examples that support the information presented here on fatalities. 

4.5.1 Settings in Which Fatalities Occurred 

Over half (57 percent) of the 161 deaths occurred in residential structures, which included apartment 

buildings, single–family residences, and the Greenbriar Nursing Home. Approximately 13 percent of the 

fatalities occurred in Joplin businesses, including retail stores and restaurants as well as the Elks Lodge 

(this statistic does not include the fatality attributed to the Golden Corral). Twelve percent of the fatalities 

happened outside of buildings, either in vehicles or outdoors (outside of any protective enclosure). Of 

those that occurred outside, one death involved a police officer killed in the line of duty on Monday, May 

23, 2011. Two others involved a person who was located outside of SJRMC dropping someone off at the 

Emergency Room (a death that other analyses may attribute to SJRMC) and an individual who was 

outside of the Greenbriar Nursing Home (a death that may arguably be attributed to the Greenbriar 

Nursing Home) when the tornado hit. Eight deaths occurred in places of worship, and three deaths took 

place in Joplin’s Stained Glass Theater. Finally, 16 deaths occurred in hospital facilities, including the 

Meadows Healthcare facility and SJRMC. 

4.5.2 Basic Causes of Deaths and Injuries 

Nearly all of the deaths (96 percent or 155 out of 161) were caused by impact–related injuries, according 

to information contained in death certificates. An impact–related cause of death means that the death 

certificate cited “multiple blunt force trauma to body” as the immediate cause of death. In speaking 

directly with the medical examiner in Joplin, NIST found that the policy in the Joplin coroner’s office was 

that autopsies were not performed unless a death was suspicious in nature. For the fatalities from the May 

22, 2011, Joplin tornado, the coroner performed visual and dental assessments and took X–rays to obtain 

the cause of death. In most cases, deaths from the tornado were labeled as “blunt force trauma.” In 

instances where the death certificate also described how the injury occurred, impact–related deaths were 

almost always listed as “struck by debris from tornado.” 

163 Community Press Kit issued for the Day of Unity observance, May 22, 2012, http://www.joplintornadoanniversary.com/ 

resources/community–press–kit.pdf. 

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Other deaths occurred due to non–impact–related factors. Three non–impact deaths occurred in single– 

family homes where two individuals died of heart attacks due to stress brought on by the storm, and one 

individual died of pneumonia.164 In all three of these cases, the storm did not damage the victim’s home, 

but the death was attributed to the storm due to the stress it caused to the individual. Heart attacks that led 

to deaths were also determined to be the cause of two of the fatalities that occurred at SJRMC. The sixth 

and last non–impact–related death was of the police officer who was killed by lightning in the line of duty 

on Monday, May 23. All of the non–impact–related deaths occurred after May 22. 

In the 71–person CDC injury sample, the extent of injuries varied significantly. Thirteen of the injured 

suffered from fungal infections (which were likely consequences of their impact–related injuries). All but 

one of these 13 individuals were either admitted to an ICU and/or spent 8 or more days in the hospital, 

thus meeting this study’s criteria for a severe injury. Explanations for injuries included the following: 

multiple abrasions, lacerations, and/or fractures from being struck or hit with flying debris. Additionally, 

the more severely injured individuals also suffered from blunt trauma, penetrating trauma, and brain 

injuries, sometimes having been knocked unconscious for some period of time. The circumstances 

leading to these injuries, both severe and non–severe, were often that individuals were thrown from their 

location (or out of the structure in which they were located) by the tornado, crushed by the structure or 

surrounding debris, or struck by flying debris of different types and sizes and with varying force. 

4.5.3 Date of Death 

Most of the people killed by the tornado (77 percent) died on the day that it occurred, May 22, 2011. This 

group included all of the fatalities that occurred at the AT&T store, Elks Lodge, Full Gospel Church, 

Golden Corral,165 Harmony Heights Baptist Church, Home Depot, Pizza Hut (the one located at 1901 

South Range Line Road), and Walmart (Store #59). Additionally, all deaths attributed to an outside 

location or to a vehicle also happened on May 22. 

In some cases, however, deaths were attributed to the location where the individual was injured, while the 

person actually died later elsewhere. Six of the 19 deaths attributed to the Greenbriar Nursing Home, for 

example, were of persons injured at the nursing home who were later transported to a hospital where they 

subsequently died from their tornado–related injuries. One of these six deaths occurred 4 days after the 

tornado, four occurred in June 2011, and one occurred in September 2011. The two individuals who were 

fatally injured at the Meadows Healthcare facility both died 2 days after the storm hit. Seventy–nine 

percent of the people who were fatally injured at home (in both single–family homes and apartment 

buildings) died on the day of the storm, while 21 percent died later in other locations (these percentages 

do not include the two individuals who suffered stress–induced heart attacks at home due to the tornado, 

and later died in a hospital). At SJRMC, five patients died on May 22, 2011 during or after the tornado. 

The nine other deaths attributed to SJRMC involved individuals who were injured at the hospital during 

the storm, including two patients who suffered stress–induced heart attacks, but died in other hospitals or 

locations days, weeks, or months later. 

164 It is unclear whether stress or taking refuge from the tornado was the cause of this person’s storm–related injury, since no 

damage occurred to the home of this fatally injured individual. 165 A death certificate indicates that one individual died at the Golden Corral, not necessarily because he or she died on the 

premises, but mainly because this was the last place where anyone saw or heard from this individual. 

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4.5.4 Demographics 

The demographic information that could be obtained for the deaths and the majority of the injuries was 

gender and age. Gender is discussed first, then the age distribution of deaths, followed by the age 

distribution of those injured by the tornado. The age analyses for deaths and injuries are presented 

separately because the age data for these two populations were provided to NIST in different ways. 

4.5.4.1 Gender 

Gender distributions were calculated for the fatalities and the sample of injured persons. Gender 

information for the fatalities was provided by the death certificates (total = 161), and the gender 

distribution for this group was as follows: 54 percent female (total = 87 dead) and 46 percent male (total = 

74 dead). Information on the gender of injured persons was provided by the ESSENCE injury dataset 

(total = 876). The gender distribution for the injured persons who were residents of either Jasper or 

Newton Counties was as follows: 52 percent female (total = 398 injured) and 48 percent male (total = 364 

injured) (total of 762). Additionally, the gender distribution for the injured who were residents of places 

outside of Jasper and Newton Counties was as follows: 48 percent female (total = 55 injured) and 52 

percent male (total = 59 injured) (total of 114). Residents of other counties (outside of Jasper and Newton 

Counties) may have been visiting Joplin at the time of the storm or staying in one of the health care 

facilities in Joplin. Overall, there was nominally an equal distribution of men and women among the 

tornado fatalities as well as in both groups of injured persons. 

4.5.4.2 Age—Deaths 

The average age of the persons killed by the May 22, 2011, Joplin tornado was 55 years old, ± 23 years 

(one standard deviation from the mean), with the median age of fatalities being 58 years old. Fig. 4–18 

illustrates the frequency distribution of the 161 fatalities attributed to the May 22, 2011, Joplin tornado, 

by age group, and compares this to a similar frequency distribution for U.S. tornado fatalities (from 

tornadoes that occurred between the years of 1996 and 2007 [Simmons and Sutter 2011]). From the May 

22, 2011, Joplin tornado, approximately 46 percent of the fatalities were aged 60 years or older, and 

further analysis revealed that approximately 38 percent of the fatalities were 65 years old or older. While 

some studies of U.S. tornadoes have found older populations (above 65 years of age) to be more 

vulnerable to casualty than other age groups (Moore 1958; CDC 1985; Sanderson 1989; Carter, Millson, 

and Allen 1989; Lillibridge 1997; Fernandez et al. 2002), Fig. 4–18 shows that the two distributions are 

different and that older people made up more of the Joplin deaths than would be expected from the U.S. 

data. Additionally, a chi-square goodness-of-fit test of the null hypothesis (i.e., that the Joplin frequency 

table is the same as the U.S. tornado table) rejects the null hypothesis with chi-square = 16.86 (df=8) at 

the 0.03 level. . 

However, it is possible that the tornado struck an area of Jasper County with a higher number of older 

individuals (aged 60 years and above). Therefore, it was important to compare the ages of Joplin 

fatalities with the distribution of ages in Joplin, as well as with the distribution of ages within the area 

most affected by the tornado. This information is presented in Fig. 4–19. 

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Chapter 4 

0 

5 

10 

15 

20 

25 

0 to 9 10 to 19 20 to 29 30 to 39 40 to 49 50 to 59 60 to 69 70 to 79 80+ 

Percentage 

Age Range 

Tornado Fatality Trends by 10–Year Age Range 

Fatalities in Joplin 

U.S. tornado fatalities, 1996-2007 

Figure 4–18. Comparison, by age, of the 161 fatalities from the May 22, 2011, Joplin 

tornado with U.S. tornado fatalities from 1996 through 2007 (Simmons and Sutter 2011). 

Figure 4–19 displays fatality rates per age group for all 161 fatalities. The graph shows fatality rates for 

two different populations: the population of the Joplin area (U.S. Census Bureau 2010) and the population 

of the six census tracts within Joplin (104, 105, 106, 107, 108, and 109) that encompassed the tornado’s 

damage path.166 A map of these census tracts is provided in Fig. 4–20. 

Because the damage path included only two blocks within census tract 109, NIST also determined the age 

distribution of the population within those two blocks plus tracts 104 through 108. No difference in age 

distribution was found between the area that included all of tract 109 versus the area that included only 

the two affected blocks of tract 109. The population of the former area totaled 29,908 people and of the 

latter area totaled 26,864 people.167 

When comparing fatality rates among each 10–year age range, Fig. 4–19 clearly shows that there was a 

disproportionate number of fatalities among those ages 40 and above. The disproportion was even more 

exaggerated for those 60 years old and above. For example, in the area that encompassed the tornado’s 

damage path, 18 people per thousand died within the age range of 80 years old and above, compared with 

rates of approximately 2 people per thousand for those aged 29 and below. 

166 Source: City of Joplin Building Division.
 167 Note: The numbers calculated from the Census tracts reasonably approximate the population estimates made by the U.S.
 

Census Bureau for the Joplin tornado damage path (about 20,820 people, U.S. Census Bureau 2012); 

www.census.gov/newsroom/emergencies/2011_tornadoes.html. 

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Chapter 4 

Tornado Fatality Rates by 10-Year Age Range
 

20 

Fatalities per Thousand People (within the

Population) 

18 

16 

14 

12 

10 

8 

6 

4 

2 

0 

Tornado Fatality Rates (Joplin Population) 

Tornado Fatality rates (Census Tract population) 

0 to 9 10 to 19 20 to 29 30 to 39 40 to 49 50 to 59 60 to 69 70 to 79 80+ 

Age Range 

Figure 4–19. Comparison of fatality rates per thousand people within two populations: 

Population 1 – the entire population of Joplin and Population 2 – the population of the 

areas within Joplin most affected by the tornado (U.S. Census Bureau 2010). 

Source: http://www2.census.gov/geo/maps/dc10map/tract/st29_mo/c29097_jasper/DC10CT_C29097_001.pdf. 

Figure 4–20. Census tracts in Joplin that were affected by tornado damage. 

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Chapter 4 

4.5.4.3 Age—Injuries 

A similar trend was found among the May 22, 2011, Joplin tornado’s injured population. From the 

ESSENCE dataset of 876 people, age range data were provided for 856 people (20 people were labeled as 

age = “unknown”). Overall, ages were provided for the 752 injured people from Jasper and Newton 

Counties and 104 injured people from areas outside of these counties (their locations were not specified 

by the data collectors). Figure 4–21 shows the injury rates for the 752 people from Jasper and Newton 

Counties, since their county location is known, and thus overall population numbers in the two counties 

could be obtained for rate calculations. Similar to the fatalities analysis, the injury rate for persons who 

were aged 65 or above was larger than (approximately double) the rates of injured persons who were less 

than 65 years old (using population statistics from the 2010 U.S. Census). 

Tornado Injury Rate for Jasper/Newton Counties by 10–Year
 

Age Range
 

0 

2 

4 

6 

8 

10 

12 

14 

16 

18 

20 

Fatalities per Thousand People (within the 

two counties' population) 

0 to 4 yrs 5 to 17 yrs 18 to 44 yrs 45 to 64 yrs 65 yrs + 

Age Range (years) 

Figure 4–21. Tornado–related injury rates by 10–year age range for residents of Jasper 

and Newton Counties (U.S. Census Bureau 2010). 

4.5.5 Summary Questions and Findings Related to Casualties 

As mentioned earlier in this section, most (96 percent, 155/161) of the 161 deaths attributed to the May 

22, 2011, Joplin tornado were caused by impact–related injuries. In these instances, the death certificate 

cited the cause of death as “multiple blunt force trauma to body.” 

Additionally, it was determined that 12 percent of the overall fatalities occurred in locations outside of 

structures, either outdoors or in vehicles. Whereas it is conceivable that individuals located outdoors 

during a severe tornado could suffer grave consequences, what protection, if any, did vehicles provide? 

Also, what wind speeds were correlated with fatal (or severe) injuries among individuals located outside 

or in vehicles during the tornado? The answers suggested by NIST’s analysis of the May 22, 2011, Joplin 

tornado will be provided in the following section (Sec. 4.6). 

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Chapter 4 

It was also determined that 87 percent of the overall fatalities occurred inside structures.168 These 

structures included both non–residential and residential structures. This finding prompts the following 

questions: What level of protection was offered by the buildings in which individuals died or were 

severely injured as a result of the May 22, 2011, Joplin tornado? Did the individuals who were fatally or 

severely injured have access to basement areas, and if so, did they take advantage of these underground 

areas? Why did 135 individuals die from impact–related or blunt–force trauma wounds to the body when 

they were located inside structures throughout Joplin? These questions will also be addressed in the 

following section. 

Finally, an analysis of the ages of those killed and injured in the tornado indicated that the age of 

individuals may have influenced their likelihood of being killed or injured. Overall, a disproportionate 

number of people aged 60 years and older died or were injured as a result of this tornado. 

4.6 THE INFLUENCE OF ENVIRONMENTAL CONDITIONS ON CASUALTIES 

The purpose of this section is to identify the factors related to the impact–related deaths and severe 

injuries that resulted from the May 22, 2011, Joplin tornado—both outside and inside of structures. This 

analysis focused primarily on the deaths that occurred as a direct result of the May 22, 2011, Joplin 

tornado, i.e., impact–related causes, rather than those caused by stress or stress–related factors. People 

who survive the physical impacts of any type of disaster experience stress, and this event–induced stress 

can and does kill a small number of survivors after the event is over, for example, by increasing the rates 

of acute myocardial infarction, other forms of ischemic heart disease, suicide rates, and more. 

Highlighting impact–related deaths that can be specifically attributed to the tornado, rather than any type 

of emergency event, will help to more clearly identify the tornado–related causal factors of death and 

injury, which can lead to improvements in life–safety systems for tornado–prone areas. Table 4–3 

provides a tally, by location, of the 154 impact–related fatalities169 used in this analysis to better 

understand the causes and patterns of deaths directly resulting from the tornado. 

Seven of the 161 deaths attributed to the May 22, 2011, Joplin tornado have been omitted from this 

analysis and were not included in Table 4–3. These seven omissions include six non–impact–related 

deaths plus the fatality attributed to the Golden Corral restaurant, which was omitted because the final 

location of injury (and death) for this individual remains uncertain. The six non–impact–related deaths, 

which were described in Sec. 4.5.2, were not included in this analysis because the causes of injury (and 

ultimately, death) in these cases were factors not specific to tornadoes. 

Some of the 154 deaths included in this analysis were of people who died days, weeks, or even months 

after the tornado hit Joplin, sometimes from illness (e.g., pneumonia) rather than solely from the injuries 

they sustained in the tornado. They were included because their death certificates specifically stated that 

they were injured by debris from the tornado. 

168 This statistic does not include the fatality attributed to the Golden Corral restaurant.
 169 As mentioned in Section 4.5.2, 96 percent (or 155 out of 161) of the deaths from the May 22, 2011, Joplin tornado were caused
 

by impact–related injuries. However, this analysis includes 154 deaths since the final location of injury (and death) for the fatality 

attributed to the Golden Corral restaurant remains uncertain. 

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Chapter 4 

Table 4–3. Number of Impact–Related Fatalities By Location (Of Death or Injury
 

That Led To Death) Resulting From The May 22, 2011, Joplin Tornado.
 

Locations of Injury/Death Number of Victims Percentage of Victims 

AT&T store 1 0.6 % 

Elks Lodge 4 2.6 % 

Full Gospel Church 4 2.6 % 

Greenbriar Nursing Home 19a 12.3 % 

Harmony Heights Baptist Church 3 2.0 % 

Home Depot 8 5.2 % 

Meadows Healthcare facility 2

b 1.3 % 

Outside (12 in vehicles) 19 12.3 % 

Pizza Hut 5 3.2 % 

Residences: apartments 12c 7.8 % 

Residences: homes (detached) 59d 38.3 % 

Stained Glass Theater 3e 2.0 % 

St. John’s Regional Medical Center 12f 7.8 % 

Walmart 3 2.0 % 

Total 154g 100.0 % 

a. Includes one individual whose final cause of death was pneumonia (died June 2011), and
 

five individuals who were injured at Greenbriar Nursing Home, were later transported to
 

a hospital, and subsequently died from tornado injuries.
 

b. Both persons died at other locations after May 22; one was already weakened by cancer. 

c. Includes one person who was injured in an apartment complex and later died in a 

hospital.
 

d. Includes 14 individuals who were injured at home and then died later in a hospital. 

e. One of these persons was injured at the theater and later died in a hospital. 

f.	 Includes seven victims who were injured at SJRMC, were later transported to another 

hospital, and subsequently died from tornado injuries.
 

g. Seven of the 161 deaths attributed to the May 22, 2011, Joplin tornado have been
 

omitted from this analysis for two reasons: 1) the cause of death was by something
 

other than an impact–related factor, and 2) the location of death was unknown.
 

All 154 deaths in this analysis can thus be traced to impact–related injuries, or more specifically, to being 

struck by debris during the storm. The immediate causes of death (as documented on the death 

certificate) ranged from multiple blunt–force trauma to the body (142 deaths) to the following more 

specific causes: multi–organ failure due to multiple blunt–force trauma to the body (1), fungal infection 

due to multiple blunt–force trauma to the body (3), internal bleeding due to blunt–force trauma (1), heart 

failure (and pre–existing heart conditions) and internal bleeding due to being thrown from the hospital 

bed and hit by debris from the tornado (1), heart attack (and pre–existing conditions) due to being struck 

by debris from the tornado (3), chronic obstructive pulmonary disease due to blunt–force trauma to the 

300 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

body (1), pneumonia due to being struck by debris from the storm (1), and end–stage renal disease (and 

pre–existing conditions) due to blunt–force trauma to the body (1). 

To support these data on the 154 fatalities, additional information was obtained from the 71–person 

sample collected by the CDC as part of its EPI–Aid Study of the May 22, 2011, Joplin tornado.170 The 

CDC data related to only a sample of the injured persons included in the original ESSENCE database (see 

Sec. 4.2 for further explanation). The focus here was on a subset of the injured persons in the CDC 

sample, namely those who had severe injuries, since it was assumed that these individuals could have died 

from their injuries without medical care. Thirty–five individuals categorized as severely injured were 

selected from the CDC sample for use in this analysis of May 22, 2011, Joplin tornado casualties. 

Persons in the sample whose injury severity was unknown were not selected. The locations where these 

35 individuals were severely injured are provided in Table 4–4. 

Table 4–4. Distribution of 35 severely injured persons (from 

the CDC sample) based upon the locations where they were 

injured in the May 22, 2011, Joplin tornado. 

Number of Severely 

Locations of Injury/Death Injured in CDC Sample 

AT&T store – 

Elks Lodge – 

Places of worship 1 

Greenbriar Nursing Home 5 

Home Depot – 

Vehicles 8 

Pizza Hut – 

Residences: apartments 1 

Residences: homes (detached) 18 

Stained Glass Theater 1 

St. John’s Regional Medical Center – 

Walmart 1 

Total 35 

The locations of the 154 fatalities and the 35 severely injured persons were plotted and shown in Fig. 4– 

22, relative to the estimated center track of the tornado (in red). It should be noted that when multiple 

fatalities or injuries occurred at the same location, ArcGIS plotted only a single icon. Table 4–3 contains 

170 Information from CDC’s injury database, specifically for those injuries categorized in this investigation as severe injuries, was 

used only as supporting data for the findings observed from the deceased. This was because the CDC dataset, although 

statistically sampled, was not sampled from a completed ESSENCE database. At the time the ESSENCE database was 

sampled, it did not contain the 876 total injuries it does currently. Also, the ESSENCE database, since it only contains those who 

visited hospital emergency rooms in Missouri, does not contain all 1,000 (or more) injuries attributed to this tornado. 

NIST NCSTAR 3, Joplin Tornado Investigation 301 
 

 

 

 

 

 

 

 

 

 

Chapter 4 

data on the numbers of deaths at each location. The map shown in Fig. 4–23 identifies the types of 

locations where the 154 deaths and 35 severe injuries occurred. 

0 0.5 1 1.5 2

Miles

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 4–22. Geographic locations of the 154 impact-related fatalities (in red) and 35 

severely injured persons (in blue) included in this analysis. 

0 0.5 1 1.5 2

Miles

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 4–23. Geographic locations (labeled by name of structure or type of setting) of 

the 154 fatalities and 35 severely injured persons included in the analysis of impact– 

related deaths and severe injuries. 

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The analysis of impact–related deaths and severe injuries focuses first on understanding the circumstances 

of those individuals who died or were severely injured outside of structures. Because they were located 

outdoors or in vehicles, they were potentially more exposed to the wind and debris environment than 

those located indoors. Consequently, it is important to understand the wind environment to which these 

individuals were exposed during this storm. Chapter 2 showed that the tornado produced wind speeds as 

high as 170 to 175 mph in some locations, but no higher than 65 mph in other locations. Therefore, the 

first questions addressed were the following: What environmental conditions did the persons who were 

located outside of structures and killed or severely injured in the storm face throughout the duration of the 

tornado emergency, and how did these conditions influence their survival? 

4.6.1 The Influence of Environmental Conditions on Casualties Outside of Buildings 

The outdoor sirens in Joplin were meant to instruct all individuals located outside to move indoors (inside 

of structures). Additionally, both of the tornado warnings disseminated by the NWS provided the 

following information on preparedness actions for people located outside of structures: 

IF IN MOBILE HOMES OR VEHICLES . . . EVACUATE THEM AND 

GET INSIDE A SUBSTANTIAL SHELTER. IF NO SHELTER IS 

AVAILABLE . . . LIE FLAT IN THE NEAREST DITCH OR OTHER 

LOW SPOT AND COVER YOUR HEAD WITH YOUR HANDS. (See 

Appendix M) 

However, 19 deaths directly attributed to the May 22, 2011, Joplin tornado were of persons located 

outside of structures or in vehicles when the storm hit. Another eight individuals who were severely 

injured were also located outside of structures in vehicles when the storm hit them.171 

To understand the environment to which these individuals were exposed, this analysis incorporated the 

estimations made of the near–surface tornado wind field in the areas where outdoor fatalities and severe 

injuries occurred. Estimations of the wind–field map were made using multiple methods, including both 

direct measurements using anemometer records and the indirect measurement techniques of the EF Scale 

and a Rankine vortex model using observed tree fall, which are further described in Chapter 2. 

The near–surface wind field was measured through a series of geographic grid points spaced at regular 

intervals throughout the areas of Joplin that were affected by the tornado. The distance between grid 

points was 0.05 miles (264 ft, 80 m), and for each grid point and time step (about every second), a 

minimum, mean, and maximum wind speed value with associated wind direction was determined. The 

range of wind speeds is assumed to be representative of the overall uncertainty in the wind speed 

estimation. The estimated maximum wind speed (including uncertainty measures of minimum and 

maximum values) at each grid point was rounded to the nearest 5 mph, loaded into ArcGIS, and overlaid 

with aerial photos. The grid points correspond with latitude and longitude coordinates to give specific 

locations for the estimated maximum wind speeds (with uncertainty) encountered in the tornado. 

The next step in the analysis involved using ArcGIS to relate the locations of fatalities and severe injuries 

to the near–surface wind–field map. An input file was developed that listed attributes of each outdoor 

171 CDC dataset via MDHSS, provided to NIST in 2012. 

NIST NCSTAR 3, Joplin Tornado Investigation 303 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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fatality and severely injured individual, including the location where they were fatally or severely injured. 

The attributes listed in the input file included the following: physical location when the storm hit (i.e., the 

physical address), date of death (for fatalities only), and cause of death (for fatalities only). 

Once the ArcGIS input file of the fatally and severely injured was developed, it was imported into the 

shapefile containing the estimated maximum wind speed information. In this stage, NIST was able to 

view the location of all outdoor fatalities and severe injuries along the tornado’s damage path. 

The next step involved manually drawing polygons to identify those locations along the tornado’s damage 

path where various wind speed ranges occurred. The wind field was used to draw polygons around zones 

with wind speeds equivalent to the EF–4, EF–3, EF–2, EF–1, and EF–0 ranges. Figure 4–24 shows the 

five polygons overlaid on the aerial photo of the tornado’s estimated center track. In the figure, the red 

area indicates an EF–4 zone (wind speeds ranged from 166 mph to 200 mph). The orange area denotes an 

EF–3 zone (wind speeds ranged from 136 mph to 165 mph). The yellow area indicates an EF–2 zone 

(wind speeds ranged from 111 mph to 135 mph). The green area represents an EF–1 zone (wind speeds 

ranged from 86 mph to 110 mph). Finally, the blue area denotes an EF–0 zone (wind speeds ranged from 

65 mph to 85 mph). ArcGIS was then used to count the number of outdoor fatalities and severe injuries 

that fell within each polygon. 

Legend

Tornado Path EF-0 EF-1 EF-2 EF-3 EF-4

0 0.5 1 1.5 2

Miles

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 4–24. The location of the five EF–Scale polygons overlaid on the aerial photo of 

the estimated tornado center track (red line). 

This analysis showed that the majority of the outdoor fatalities (63 percent) and of the sample of severely 

injured persons (88 percent) was located in the areas where the tornado was estimated to have produced 

the strongest wind speeds (i.e., EF–3 or EF–4 wind speeds) (see Table 4–5). Fifty–eight percent of 

fatalities, supported by 88 percent of the sample of severe injuries, occurred in the EF–4 zone. 

In the highest estimated wind speed zones (EF–3 through EF–4, where wind speeds ranged from 136 mph 

to 200 mph), information gathered on the deceased and severely injured reflected individuals being 

sucked, ejected, or thrown from their cars. Interviews with the severely injured provided detailed 

information about vehicle windows getting blown out or broken by winds or debris, providing 

opportunities for the storm to push or pull individuals into the debris field and/or send debris flying into 

cars, causing severe blunt–force trauma or unconsciousness. This makes it clear how individuals could be 

304 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Table 4–5. Wind speeds associated with fatalities and severe injuries 

among people located outside of buildings. 

Wind Speed, mph 

(EF-Scale) Number of Fatalities Percentage 

Number of 

Injuries Percentage 

65–85 

(EF–0) 

4 

(all outside) 

21 0 0 

86–110 

(EF–1) 

2 

(1 vehicle, 1 outside) 

11 1 12 

111–135 

(EF–2) 

1 

(outside) 

5 0 0 

136–165 

(EF–3) 

1 

(vehicle) 

5 0 0 

166–200 

(EF–4) 

11 

(10 vehicle, 1 outside) 58 7 88 

killed or severely injured from blunt–force trauma to the body either inside or outside of vehicles. With 

the exception of one individual located outside of the Greenbriar Nursing Home, all of the fatally and 

severely injured persons (outside of structures) in the highest estimated wind speed zones were located 

inside vehicles when the storm hit. This suggests that being caught outside structures and exposed to 

tornadic wind speeds higher than 165 mph can be very dangerous, due to the tornado’s ability to send 

heavy debris flying into vehicle windows and lift individuals from their vehicles into the storm’s debris 

wall. 

Fatalities and severe injuries, although in lower numbers, were also found in zones with estimated wind 

speeds less than 136 mph. One person was killed outside of the emergency room entrance to SJRMC in 

an EF-2 zone (where winds were estimated to range from 111 mph to 135 mph). He was thrown from his 

(outdoor) location and died when a car landed on top of him. Additionally, three individuals died or were 

severely injured outdoors in an EF-1 zone (winds ranging from 86 mph to 110 mph). One of these 

individuals (who died) was located outdoors (without any shelter), attempting to catch her dog who had 

run away from the house. The other two individuals, one of whom died, were located outside of Walmart 

(Store #59), each located in a pick–up truck. However, because Walmart was such a large structure, 

according to information provided in Chapter 3, wind speeds varied depending on a person’s location in 

or around the store. Consequently, it was difficult to determine the maximum estimated wind speed to 

which these individuals were exposed. As shown in Fig. 4–25, the uncollapsed north half experienced a 

lower maximum wind speed of 120 mph ± 20 mph (at a northerly wind direction), while the collapsed 

south half experienced a higher maximum wind speed of 165 mph ± 20 mph (at a west-northerly wind 

direction). ArcGIS plotted the store location at one data point, placing all deaths near or around the 

northern half of the building (i.e., the half that sustained a lower maximum wind speed). However, if the 

trucks had been located in the parking lot on the west side of the building (see Fig. 4–25), then they could 

have been exposed to estimated near–surface wind speeds ranging from 85 mph to 135 mph. 

NIST NCSTAR 3, Joplin Tornado Investigation 305 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

N 

Collapsed 

!rea

Walmart South Half 

Parking Lot 

Walmart North Half 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 4–25. Overhead view of tornado damage to Walmart Store #59. 

Finally, Table 4–5 shows that four fatalities occurred outdoors in estimated wind speeds between 65 mph 

and 85 mph. It was of interest to understand where these people were located when the storm hit and why 

they died in these EF–0 wind speeds. All four persons were located outdoors (and outside of vehicles) 

when the storm hit. Three of the fatalities were located in a drainage ditch at or near 3877 East 27th 

Street in Joplin. The cause of these deaths was determined by the Joplin coroner to be blunt–force 

trauma; however, it is unclear what role, if any, water inside the drainage ditch played in the outcomes. 

NWS instructions provided in tornadoes state that “If no shelter is available . . . lie flat in the nearest ditch 

or other low spot and cover your head with your hands” (see Appendix M for further information). 

However, this ditch did not provide adequate protection for these three individuals, even at a location that 

was not exposed to the highest wind speeds. Finally, an additional fatality was found at 20th Street and 

Sergeant Avenue, also outdoors. It is unclear whether the individual was killed at this location by EF–0 

wind speeds or if he or she encountered the storm in a nearby location with higher wind speeds (i.e., in an 

EF–1 zone) and was thrown to 20th Street and Sergeant Avenue. 

To summarize this section on casualties outside of buildings, NIST found that overall, the majority of the 

outdoor fatalities (and severe injuries) occurred in areas subjected to the highest wind speeds. The 

information presented in the tables and figures above suggests, as expected, that outdoor fatalities and 

severe injuries markedly increased in the wind zone rated as EF–4 (i.e., in winds greater than 165 mph). 

At these wind speeds, vehicle windows broke, causing individuals to be ejected from their vehicles or 

struck by flying debris through broken windows. 

The majority of impact–related deaths in the May 22, 2011, Joplin tornado, however, occurred inside 

structures throughout the tornado’s damage path. Therefore, it is important to understand the types of 

buildings in which these individuals were located and the protection offered by these buildings, given the 

tornadic wind environment to which the structures were exposed. The following section examines the 

environmental conditions, including building performance and wind environment that persons killed and 

306 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

severely injured indoors encountered during the tornado, and how these conditions may have influenced 

their survival. 

4.6.2 The Influence of Environmental Conditions on Casualties Inside of Buildings 

NWS warning information advises individuals to seek substantial shelter if they are outside or in vehicles. 

In the May 22, 2011, Joplin tornado, 87 percent of the fatalities attributed to impact–related injuries 

involved individuals located indoors during the storm. This section addresses the following question: 

Why did 135 individuals die from impact–related or blunt–force trauma wounds to the body when they 

were located inside structures throughout Joplin? To answer this question, NIST analyzed the 

performance of the structures in which people died, the wind environment to which these buildings were 

exposed, and the actions of the people inside these buildings. Information on wind speeds, building 

damage, and the actions taken by building occupants will be provided (when known) to assess the level of 

protection afforded by the building when the tornado struck. As in previous sections, information from 

the severe injury sample will be used, where possible, to support findings drawn from the fatalities. 

To obtain information on wind speeds, ArcGIS was used in conjunction with the estimated wind–field 

map (described in Sec. 4.6.1, above). All physical locations (i.e., physical addresses) of the buildings in 

which deaths occurred were queried using ArcGIS. Once each building was located on the aerial map in 

ArcGIS, the adjacent wind–field estimate (or point) was queried to obtain the mean, minimum, and 

maximum wind speeds at that point. In instances where a building fell between two wind estimate points, 

the lower estimates were collected for that building. 

Additionally, ArcGIS was used to obtain information on building damage, based on a database created by 

Pictometry® . The database listed the damage sustained by individual buildings using four main damage 

categories (light, medium, heavy/totaled, and demolished). These categories were assigned to buildings 

by analyzing the differences between pre– and post–storm aerial and oblique imagery of the Joplin 

area. 172 Following are brief descriptions of the levels of damage that characterize each category: 

	 Light: Visible damage to the building envelope, including the loss of a small portion of the roof 

covering. 

	 Medium: Loss of a small portion of the roof system, comprising the loss of some roof covering 

and structural sheathing and damage to some roof trusses. 

	 Heavy/Totaled: Loss of a significant portion of or the entire roof system, thus exposing the 

building interior to weather damage and compromising the lateral bracing system for walls, but 

walls remain standing. 

	 Demolished: Roof and walls collapsed, entire structure might be shifted off of the foundation and 

collapsed. 

When available in the Jasper County GIS database or via NIST analysis documented in Chapter 3, 

additional information about individual buildings was obtained, including the year built, type of structure, 

172 E. Stitz, Regional Technical Manager – Central Region, Pictometry®. Personal Communication, October 2012. 

NIST NCSTAR 3, Joplin Tornado Investigation 307 
 

 

 

 

 

Chapter 4 

number of stories, and the presence of an “underground refuge area” (i.e., basement or partial basement) 

or crawl space. For the most part, this additional building information was available in the GIS database 

for residential structures only. Figure 4–26 shows an example of the GIS database damage levels 

distinguished by color. 

Data Source: Pictometry®. Used with Permission. 

Figure 4–26: A sample of the Pictometry® database damage levels 

distinguished by color. 

308 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

Chapter 4 

Finally, for each structure, using the interview narratives referenced in Sec. 4.4, information was collected 

on where inside the building the decedent(s) took refuge (if known). For example, if a basement was 

available inside the structure, it was important to know whether the deceased took refuge in the basement 

or elsewhere. In addition, if the building had a designated “refuge” area, it was important to note whether 

decedents used these areas. 

4.6.2.1 Non–Residential Structures 

Table 4–6 presents information on the wind environment, the building type (including building damage), 

and the actions taken by the deceased (if known) for seven non–residential buildings in which people 

died. Information concerning Home Depot, Walmart, and SJRMC, also non–residential structures where 

individuals died but not included in Table 4–6, will be discussed in greater detail later in this section, 

since they were buildings with more complicated wind speed gradients. These three locations were also 

discussed in detail in Chapter 3, and some of the information developed for that discussion is used here to 

provide more comprehensive descriptions of the damage they sustained and its influence on the deceased. 

Table 4–6. Details on the wind environment, building type, building damage, and actions 

taken by the deceased for seven buildings in which people died in the May 22, 2011, 

Joplin tornado. 

Building 

Wind Speed a 

(max range 

mph) Building Type 

Building 

Damage 

Basement 

(Y/N) 

Circumstances of 

the Deceased 

AT&T store 160, 115–200 Metal frame walls 

with brick facade 

Unrated No Crushed in back 

office 

Elks Lodge 170, 125–210 Wood frame Demolished No Attempting to run 

to cooler 

Full Gospel 

Church 

150, 110–195 Wood frame Demolished No Located in nursery 

Harmony Heights 

Baptist Church 

160, 110–195 Concrete masonry 

unit/wood frame 

walls with wood 

roof trusses 

Demolished No Located in nursery 

and library 

Meadows 

Healthcare facility 

100, 70–135 Wood frame 

connecting 

structure; rest of 

building unknown 

Heavy/ 

Totaledb 

No (Not known) 

Pizza Hut 170, 125–210 Wood frame Demolished No Thrown from 

cooler 

Stained Glass 

Theater 

170, 125–210 Unreinforced 

masonry walls with 

brick facade 

Demolished Yes Above–ground 

theater area 

(survivors in 

basement) 

a. Estimated from the wind field model presented in Chapter 2. The first value is the best estimate of the maximum wind 

speed at the building, followed by the range of the estimated maximum wind speed including uncertainty. 

b. It is unclear why this building received a “Heavy/Totaled” damage rating since the majority of the roof was intact, except 

for the small connecting structure on the south end of the building. Additionally, this building was surrounded by other 

buildings with damage rated as light or medium only. 

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Chapter 4 

All seven buildings included in Table 4–6, with the exception of the Meadows Healthcare facility, were 

exposed to estimated maximum wind speeds of 150 mph ± 20 mph to 170 mph ± 20 mph, with the 

estimated maximum wind speeds ranging from 110 mph ± 20 mph to 195 mph ± 20 mph in some cases, 

and 125 mph ± 20 mph to 210 mph ± 20 mph in other cases. The buildings were wood–frame, 

unreinforced masonry, or metal frame with brick façade structures, and were not required to be built to 

withstand these levels of wind speed (see Chapter 3, Sections 3.1.4 and 3.1.5, for information on building 

code requirements related to wind speed, nationally and in Joplin). As a result of the winds to which they 

were exposed and their building types, six of these seven buildings were categorized as “demolished.” 

The AT&T store was not rated by the GIS database; however, the picture provided in Fig. 4–27 clearly 

shows a structure that was “demolished” by the storm. 

E. 17th Street 

S. Range Line Road 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 4–27. 

Aerial photo 

showing the 

AT&T store 

demolished 

by the storm 

(outlined in 

red). 

In all six buildings classified as demolished, roofs blew off, walls collapsed, and the internal structures of 

the buildings collapsed. Specifics on each building are provided here based upon visual observations of 

aerial photos, shown in Fig. 4–27 to 4–32. 

The first of the buildings in Table 4–6, the AT&T store, sustained complete structural failure with loss of 

the metal roof decks; disconnection, displacement, and collapse of the entire roof truss system; and 

complete collapse of all exterior unreinforced CMU walls. In addition, most building components 

collapsed in place (into all areas of the building interior). 

As shown in Fig. 4–28, the Joplin Elks Lodge sustained complete demolition, with disconnection and loss 

of the entire roof system and complete collapse of the structural wood frame. Similar to the AT&T store, 

most building components collapsed into the building’s interior due to the storm. 

310 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

Chapter 4 

© 2011 Tim Marshall. Used with Permission. 

Figure 4–28. Tornado damage to the Joplin Elks Lodge. 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 4–29. Aerial photo showing damage to the Full Gospel Church building. 

NIST NCSTAR 3, Joplin Tornado Investigation 311 
 

 

 

 

Chapter 4 

Indiana Avenue 

© 2011 GeoEye. Used with permission. 

Enhancements by NIST. 

Figure 4–30. Aerial photo showing damage to Harmony Heights Baptist Church. S. Range Line Road 

© 2011 Geoeye. Used with Permission. 

Enhancements by NIST. 

Figure 4–31. Aerial photo showing damage to the Joplin Pizza Hut. 

312 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

W. 26th Street 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 4–32. Aerial photo showing damage to the Stained Glass Theater. 

The Full Gospel Church (Fig. 4–29) was completely demolished, with the entire wood roof system 

disconnected from the supporting wood–frame walls and disintegrated; and all supporting walls 

disconnected from the concrete slab foundation and collapsed. Additionally, a significant amount of 

debris, mostly building materials, ended up in all areas of the building’s interior. 

The Harmony Heights Baptist Church was completely demolished by the storm. The building sustained 

the loss of the entire wood roof system and complete collapse of all exterior CMU/wood frames. Most 

debris from the roof and walls ended up in all areas of the building’s interior. The damage is shown in 

Fig. 4–30. 

Through observation of aerial photos (Fig. 4–31), it was found that the Joplin Pizza Hut was completely 

demolished as a result of the tornado. The building’s entire roof system disintegrated and all wood–frame 

supporting walls collapsed. Also, building materials from collapsed components fell into the interior of 

the building. 

Finally, the Stained Glass Theater sustained complete demolition, with disconnection (and disintegration) 

of the wood roof system and partial collapse of the exterior CMU walls. Most building materials from 

damaged building components ended up in all areas of the building interior. Damage to the building can 

be seen in Fig. 4–32. 

The Meadows Healthcare facility was exposed to lower wind speeds than the other buildings in Table 4– 

6. Even so, the damage to this structure was rated as “heavy/totaled,” and is shown in Fig. 4–33. Two 

fatalities occurred in this building. One of these two victims had reportedly been ill with cancer prior to 

the storm.173 It is not known if the other victim was also ill when the storm hit; however, both individuals 

173 According to information that NIST found through a LexisNexis® search of obituaries. 

NIST NCSTAR 3, Joplin Tornado Investigation 313 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

died the day after the tornado. One possibility is that the tornado, even at lower wind speeds, caused 

sufficient damage to the building to cause individuals who were already relatively frail to pass away. 

Figure 4–33. Aerial photo 

showing damage to the 

Meadows Healthcare facility 

(outlined in red). 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

In all of the demolished buildings, the persons killed or severely injured were located above ground. 

Only one of the eight buildings discussed in this section, the Stained Glass Theater building, contained an 

underground space or basement that was available to patrons. In that structure, no evidence was found 

that any of those killed were located in the basement at the time the tornado hit. Additionally, there was 

one individual in the severely injured sample (provided by the CDC) who was located above ground in 

the entrance or doorway area of the theater when injured. 

In all cases but the Meadows Healthcare facility, the buildings were exposed to wind speeds that resulted 

in their complete demolition. Victims in these buildings were exposed to flying debris or falling building 

materials, and in some cases, were sucked from the building out into the storm. At these high wind 

speeds (i.e., EF–3 and EF–4 zones), the buildings were so severely damaged that the individuals located 

above ground in these structures were at high risk of blunt–force trauma from the debris field produced by 

this storm. 

Box–Type Structures: Walmart and Home Depot—

Lives were also lost in two larger structures located in the tornado’s damage path. These include a 

Walmart and a Home Depot. 

Walmart 

Walmart Store #59 was a one–story, box–type system building with a long–span, flexible–diaphragm 

metal roof. The building measured approximately 573 ft from north to south and 290 ft from east to west, 

and the structural system comprised the roof system, a series of individual plane steel frames, and the 

perimeter walls. For further information on the building’s construction, please see Chapter 3. 

On May 22, 2011, the area that people were told to go to for refuge, and where a large number of 

individuals took refuge (labeled here as the “refuge area”), was located at the back of the store, along the 

314 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

east wall. Figure 4–34 identifies this area with a red square circled in white. The refuge area was located 

in the southeastern part of the building, within the collapsed south half of the building that received the 

higher wind speeds (estimated maximum of 160 mph). As noted in Chapter 3, the refuge area was not a 

hardened area, but simply an area of the store in which individuals could congregate during a tornado. 

N 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 4–34. Aerial photo showing damage to Walmart Store #59, including the red box 

(circled in white) to indicate the store’s refuge area. 

Within the collapsed area, where patrons are known to have congregated during the tornado, the building 

lost all of its roof decks and joists. Although the majority of the joist girders remained in place, and all 

columns remained in place, large sections of the leeward concrete masonry walls collapsed inward. The 

exterior wall of the refuge area was one of the walls that collapsed inward, and it fell into the area where 

50 to 60 people had congregated. According to an interviewee, the collapsed wall closest to the refuge 

area rested on a set of cabinets nearby, creating a D–shaped pocket of safety. 

The wind and debris hazard produced by this tornado, as estimated by the wind field model presented in 

Chapter 2, exceeded the conditions that this store was designed to withstand. In consequence, the 

Walmart building, specifically the southern half of the building in which many people were located, 

suffered complete collapse, which can be categorized as “demolished” (similar to most of the buildings 

discussed in the preceding section). Additional information on the possible failure sequence that led to 

the building’s collapse can be found in Chapter 3. The store did not have an underground location (or 

basement) or an indoor storm shelter where patrons could shelter from the storm. The structural collapse 

of a portion of the Walmart building on May 22, 2011, is thought to have caused three fatalities and an 

unknown number of injuries among the approximately 200 occupants located inside the building during 

the storm. However, no official information was found by NIST on the exact location inside the store of 

the three fatalities. 

NIST NCSTAR 3, Joplin Tornado Investigation 315 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

Home Depot 

The Home Depot store was a one–story, box–type system building with a long–span roof. The building 

had the following approximate dimensions: 470 ft from north to south by 250 ft from east to west, with a 

mean roof height of 28 ft. The building’s structural system comprised the roof system, a series of five 

individual plane steel frames, and the perimeter tilt–up concrete wall panels. For further information on 

the building’s construction, please see Chapter 3. 

The Home Depot’s perimeter tilt–up walls and roof system completely collapsed during the tornado. In 

total, 63 of the 73 wall panels collapsed either inward or outward, leaving 10 standing after the storm. 

Due to the wind and debris damage it sustained, this building was categorized as “demolished” in the GIS 

database. An aerial photo of the damage to the Home Depot is shown in Fig. 4–35. 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 4–35. 

Aerial photo 

showing 

damage to the 

Home Depot 

(outlined in red). 

Media accounts indicated that 35 employees and customers gathered inside the training room at the back 

of the store before the storm hit. According to the store’s emergency procedures, the training room was 

the designated refuge location in the event of severe weather, such as tornadoes. Death certificates 

obtained by NIST showed that a total of eight fatalities occurred at the Home Depot; however, interviews 

with Home Depot survivors reflected that seven deaths occurred inside the structure. According to the 

interviews, the deaths were likely the result of the structural collapse located toward the front of the store 

in the lumber area. The number of injuries that resulted from the structural collapse of the Home Depot is 

unknown. 174 

The wind and debris hazard produced by this tornado, as estimated by the wind field model presented in 

Chapter 2, exceeded the conditions that this building was designed to withstand. In consequence, the 

Home Depot suffered a complete collapse. Additional information on the possible failure sequence that 

led to the building’s collapse can be found in Chapter 3. Similar to Walmart, the Home Depot did not 

174 According to interviews with Home Depot corporate and survivors, Home Depot does not know how many people were in the 

store that afternoon, only that 35 were in the refuge area. 

316 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

have an underground location (or basement) or an indoor storm shelter where patrons could shelter from 

the storm. 

Critical Facility: St. John’s Regional Medical Center—

As described in Sec. 4.4.2, SJRMC comprised eight buildings situated in north and south complexes. The 

focus here is on the two towers, West and East, which were part of SJRMC’s north complex, because 

patients, visitors, and hospital staff were located in these towers on the evening of May 22, 2011. 

The West Tower was constructed in 1965 and had a seven–story, cast–in–place reinforced concrete frame 

with a mean roof height of 86.7 ft. The East Tower was built in 1985 and had a nine–story steel frame 

with a 109.3 ft mean roof height. The East Tower was connected to the West Tower along the latter 

building’s entire elevation by a 10–story steel frame structure that housed the elevator shafts serving both 

towers. This connecting elevator tower was the tallest structure at SJRMC with a 126.8 ft mean roof 

height. Thus, even though they had independent structural systems, the two towers had a common, 

connecting interior floor plan. Additional information on the construction of these towers can be found in 

Chapter 3. 

During the tornado, the towers were exposed to an estimated maximum wind speed of 170 mph (the EF–4 

wind speed range). As mentioned in Chapter 3, the towers primarily sustained damage to their building 

envelopes and interiors, but did so without structural collapse. The damage to these buildings included 

the breakage of almost all vertical glass; damage to the roof systems, including the loss of aggregate roof 

ballast, which became wind–borne debris that further damaged the facility and the surrounding areas (see 

Chapter 3); damage to the interiors, including the breakage or collapse of interior partitions, suspended 

ceiling systems, furniture, fixtures, and equipment; damage to sections of gypsum–metal stud walls 

surrounding the elevator shaft and to the elevator equipment itself; and water and debris infiltration onto 

the floors. A view of the interior damage can be seen in Fig. 4–36. 

Figure 4–36. 

Damage to the 

interior of 

SJRMC. 

© 2011 Curtis Lynn Geise. Used with Permission. 

NIST NCSTAR 3, Joplin Tornado Investigation 317 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Interviewees noted the amount of debris on floors throughout the two towers, mentioning the time it took 

to free people from under the debris. An interviewee who had been on the 6th floor noted that “a couple 

of people who had walls on top of them, meaning leaning over them, they were compressed under them. 

Some people—two of them were underneath one of those 2–inch or inch and a half water mains that I told 

you about for fire suppression. It was falling right on them; they were gonna be hypothermic pretty 

quickly so we had to move them. One of those was trapped and it took me probably 15 minutes, 10 

minutes, to get her loose” (NIST Interview 6). In the Emergency Room on the ground floor of the 

hospital, interviewees mentioned water up to their ankles and live wires sparking above them (NIST 

Interview 2). 

In addition to damaging the building envelopes and interiors at SJRMC, the tornado hazards (high wind 

speeds and wind–borne debris) damaged local EDE facilities, resulting in a region–wide loss of electrical 

power in Joplin, including loss of the main electrical power supply to SJRMC. The tornado also 

collapsed SJRMC’s Emergency Generator building that housed the backup power generator and other 

electrical equipment, which resulted in a total loss of electrical power throughout this critical facility. 

Due to the loss of power and the magnitude of the internal damage to the two hospital towers, hospital 

staff on each floor made individual decisions (without the assistance of hospital–wide evacuation 

announcements) to evacuate the structures. According to the hospital’s risk manager, it is rare that a 

hospital requires full evacuation. If only a unit or wing of a hospital requires evacuation, staff will 

coordinate a horizontal evacuation of patients and visitors to a safer area (or compartment) on the same 

floor. However, after the tornado on May 22, “the building basically was shut down. Nothing was 

working inside the building” (NIST Interview 7), requiring a full (vertical) evacuation of the hospital. 

Eventually, firefighters and hospital staff walked throughout the towers requesting that anyone who had 

not yet evacuated begin to do so. Due to the loss of power throughout the towers, and thus, the loss of 

elevators and lighting, hospital staff and others evacuated patients and injured individuals through 

darkened hallways and down staircases using improvised stretchers (i.e., wheelchairs, hospital doors that 

had been blown off their hinges, backboards, a device called a Med Sled®, and mattresses). In the dark, 

staff used flashlights and cell phones for illumination (see Sec. 4.4.2). 

All five individuals who died at SJRMC on May 22, 2011, had impact–related causes listed on their death 

certificates (i.e., multiple blunt–force trauma to the body), and four of the five were patients located in 

ICUs. The causes of death for these patients were determined by the Joplin coroner to be blunt–force 

trauma; however, it is unclear what role, if any, their pre–existing conditions or the loss of ICU medical 

support systems played in these outcomes. One additional patient died on the third floor, but this 

individual was not in intensive care (NIST Interview 7). His or her death was also due to multiple blunt– 

force trauma to the body. 

In addition to the five patients who succumbed at SJRMC, seven people were injured at the hospital, but 

died in other health care facilities days, weeks, or months later. These seven deaths were similarly 

attributed to multiple blunt–force trauma to the body. 

Although the buildings at SJRMC were constructed in different phases, the newest building was designed 

in accordance with the 1990 BOCA NBC, which specified a design wind speed of 85 mph. Even after 

this speed was adjusted upward due to the hospital’s required functionality as a critical facility, the wind 

speeds used in designing this and other SJRMC buildings were still significantly less than the wind 

speeds encountered at SJRMC during this tornado. The exceptionally high tornado wind speed estimated 

318 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

at SJRMC during the May 22, 2011, tornado, combined with the associated wind–borne debris hazard, 

presented environmental conditions that well exceeded the conditions planned for in designing the 

hospital’s buildings. These conditions caused the loss of both main and backup power supplies (including 

interior lighting for the entire facility) and the wind and debris–impact damage to the buildings’ interiors. 

This damage, in turn, led to (a) deaths and severe injuries inside the hospital on May 22, some of which 

led to deaths days, weeks, or months later, and (b) extremely hazardous conditions during a necessary full 

building evacuation. 

4.6.2.2 Residential Buildings 

In addition to the lives lost in non–residential buildings, lives were also lost in residences throughout the 

Joplin area. This section focuses on the fatalities that occurred in single–family homes and apartment 

complexes as a result of the May 22, 2011, Joplin tornado. Data from severe injuries that occurred in 

residences, obtained from the CDC sample of severe injuries, are used to support the findings relating to 

fatalities. 

Table 4–7 presents information on the wind environment, building type, building damage, and protective 

actions taken by the deceased (if known) for residential buildings throughout the tornado’s damage path. 

Instead of determining wind speed point estimates for each residence, the EF–Scale polygons (discussed 

in Sec. 4.6.1) were used to identify the numbers of fatalities in single–family homes and apartments that 

occurred within EF–3 and EF–4 wind speed zones. 

Table 4–7. Details on the fatalities, wind environment, building type, building damage,
 

and actions taken by the deceased for residential buildings impacted by the
 

May 22, 2011, Joplin tornado.
 

Type of Residence 

and Total Deaths 

Deaths by Wind 

Speed Zone 

Building 

Type 

Deaths by 

Building 

Damage 

Decedents 

’ Access to 

Basement 

Circumstances of 

the Deceased 

Single–family 

homes 

(59 deaths) 

53 deaths in EF–3 

or EF–4 zones 

(36 in EF–4 zone) 

Wood frame 54 in 

demolished, 

5 in heavy/ 

totaled 

56 none, 

3 partial 

All above ground 

when storm hit; 

only 20 known to 

take internal refuge 

Apartments 

(12 deaths) 

12 in EF–3 or EF–4 

zones 

(9 in EF–4 zone) 

Wood frame 12 in 

demolished 

12 none All above ground 

when storm hit; 

only 2 known to 

take internal refuge 

Greenbriar Nursing 

Home 

(19 deaths) 

19 in 170 mph, 

(EF-4 range) 

Unreinforced 

masonry 

with wood 

roof trusses 

19 in 

demolished 

19 none Located in hallway 

Single–Family Homes—

NIST found that 59 people died in single–family homes as a result of the tornado. These 59 people died in 

a total of 51 homes along the damage path, since six sets of 2 people and one set of 3 people were 

together in the same houses when the tornado hit. A large majority of these 59 deaths (53 out of 59, or 90 

NIST NCSTAR 3, Joplin Tornado Investigation 319 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

percent) occurred in homes that were exposed to wind speeds characteristic of EF–3 or EF–4 wind zones 

(i.e., estimated maximum wind speeds ranging from 136 mph ± 20 mph to 200 mph ± 20 mph, on 

average). Of the six remaining deaths, which occurred in lower wind–speed zones, four were in houses 

that, despite the lower wind speeds, were still judged to have been “demolished.” All 59 fatalities 

occurred in homes where the building damage was rated as either “heavy/totaled” or “demolished,” with 

the majority of fatalities (54 out of 59 or 92 percent) occurring in homes rated as “demolished.” 

The majority of the single–family homes at which fatalities occurred are thought to have been wood– 

frame structures. The majority of the fatalities in single–family homes (38 out of 59, or 64 percent) 

occurred in homes built between the years of 1985 and 1999. Only 5 percent of the fatalities occurred in 

homes built since 2000, and 31 percent of the fatalities (18 out of 59) occurred in homes built in or before 

1950. A majority of the fatalities (50 out of 59, or 85 percent) occurred in one–story homes (ranch style, 

older conventional style, or new conversion style homes), and the remaining nine fatalities occurred in 

homes that were one and one–half or two stories in height (older conventional or older multi–family 

homes175). 

Only 3 of the 59 persons killed had access to an underground level of the house. In all three of these 

cases, the home was equipped with a partial basement, and NIST found that at least two of these three 

individuals did not access their basements before the storm hit. The circumstances of the third death, 

including the location where he or she took refuge, if any, are unknown. 

The findings concerning fatalities in single–family homes are supported by the experiences of the 18 

individuals from the CDC sample who were severely injured in such structures. All 18 of these 

individuals were located in one–story or one–and–one–half–story single–family homes that were rated as 

“demolished” by the storm. Additionally, none of these individuals had homes equipped with partial or 

full basements. For the severely injured in this sample, homes were built as early as 1910 and as late as 

2005. 

However, there were people who survived in single–family homes located within the EF–4 wind zone. 

NIST spoke with 27 such individuals. Of these 27, 11 took shelter in basements (full or partial, located in 

newer homes). Just one of the 27 interviewees sheltered in a crawl space; as noted earlier in the chapter, 

the use of crawl spaces was rare in the May 22, 2011, Joplin tornado, even though a large number of the 

damaged homes within the tornado’s path were equipped with them (80 percent). The rest of the 27 

individuals (total of 15) survived while located in internal spaces on the first floor of their home, 

including in internal closets or laundry areas (3 people), internal hallways (5 people), or internal 

bathrooms (7 people). Half of these 15 people, who took refuge in internal, first–floor spaces, specifically 

noted that the building damage provided some type of protection for them from the storm (i.e., the 

building wall fell down and provided a tent–like structure over them). Two others who sought internal, 

first–floor refuges suffered severe injuries in the storm. 

In sum, people did survive in their homes within areas subjected to EF–4 or higher wind speeds. 

Additionally, not all of these survivors were located underground during the storm. However, 

175 These are characterized as single–family homes because they were not apartment complexes. The term “multi–family home” is

meant to describe a semi–detached home where two single–family homes share one “party” wall.

320 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

interviewees who were above ground in these wind speed zones mentioned suffering severe injuries or 

being unintentionally protected by the building damage around them. 

Apartment Complexes—

NIST found that 12 people died in three different apartment complexes as a result of the tornado. These 

three sites included three–story garden–style apartments located at 2001 Connecticut Avenue (identified 

by the solid red line in Fig. 4–37), two–story garden–style apartments located at 2034 Connecticut 

Avenue (outlined by the red, dashed line in the same figure), and two–story garden–style apartments 

located at 2020 Hampshire Terrace (shown in Fig. 4–38). At all three sites, occupants were exposed to 

wind speeds characteristic of EF–3 or EF–4 wind zones (i.e., estimated maximum wind speeds ranging 

from 136 mph to 200 mph, on average). All 12 fatalities occurred in apartment complexes that were rated 

as “demolished.” These complexes were primarily wood–frame structures, and were not equipped with 

underground or aboveground protection areas. Consequently, all of those killed were located above 

ground when the storm hit, and at least one was known to be located inside his apartment (floor level 

unknown). 

E. 20th Street 

Connecticut Avenue 

© 2011 Geoeye. Used with Permission. 

Enhancements by NIST. 

Figure 4–37. Aerial photo showing damage to two apartment 

complexes in Joplin at 2001 Connecticut Avenue (outlined by solid red 

line) and 2034 Connecticut Avenue (within dotted line). 

The findings regarding fatalities in apartment complexes were supported by the one severely injured 

individual (from the CDC sample) who was injured in the apartments at 2001 Connecticut Avenue. 

Along with its tornado warnings for the Joplin area, issued at 5:09 p.m. and 5:17 p.m. on May 22, 2011, 

the NWS provided the following preparedness information for people located indoors: 

NIST NCSTAR 3, Joplin Tornado Investigation 321 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

E. 20th Street 

New Hampshire Avenue 

© 2011 Geoeye. Used with Permission. 

Enhancements by NIST. 

Figure 4–38. Aerial photo showing damage to the
 

Hampshire Terrace apartments.
 

THE SAFEST PLACE TO BE DURING A TORNADO IS IN A 

BASEMENT. GET UNDER A WORKBENCH OR OTHER PIECE OF 

STURDY FURNITURE. IF NO BASEMENT IS AVAILABLE . . . 

SEEK SHELTER ON THE LOWEST FLOOR OF THE BUILDING IN 

AN INTERIOR HALLWAY OR ROOM SUCH AS A CLOSET. USE 

BLANKETS OR PILLOWS TO COVER YOUR BODY AND 

ALWAYS STAY AWAY FROM WINDOWS. (See Appendix M) 

Because residential basements were scarce in Joplin,176 it was important to understand whether any of 

those who were fatally or severely injured in homes or apartments sought shelter on the lowest floor of 

the building in an interior room or hallway. Data collected on the fatalities in single–family homes and 

apartments showed that 20 of the 71 individuals were known to have taken refuge on the lowest floor of 

the building and in an internal location (the locations of 41 individuals were unknown177). Data collected 

on those severely injured in single–family homes and apartments showed that 12 of the 19 individuals 

were known to have taken refuge in internal locations on the lowest floor (2 individuals’ locations were 

unknown). What these findings show is that some individuals in residential facilities, both inside and 

outside of internal (first–floor) shelters, were severely injured or killed in this tornado. 

176 Only three of the 71 individuals who died in residences in the Joplin tornado had access to basements. Two of these three 

individuals did not take refuge in the basement before the storm hit, and the other individual’s location within the home is 

unknown. 

177 The locations of the two fatalities in apartments who took internal refuge (in a bathroom) were counted as “unknown” because it is 

unclear whether they were in a ground–floor apartment. 

322 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

Greenbriar Nursing Home— Multi–family housing 

Nineteen individuals died in the Greenbriar Nursing Home. The structure was exposed to an estimated 

maximum wind speed of 170 mph ± 20 mph. The building was an unreinforced masonry structure. 

Damage to the structure, rated as “demolished,” is shown in Fig. 4–39. It is unclear where the 19 

fatalities were located within the Greenbriar; however, there were also five individuals (from the CDC 

sample) located at the Greenbriar who sustained severe injuries and were located in the hallway, a 

bedroom, and a doorway inside the structure. 

W. 26th Street 

S. Moffet Avenue 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 4–39. Aerial photo showing damage to the Greenbriar Nursing Home. 

Both commercial and residential buildings in which people died were demolished or very heavily 

damaged by this storm. Larger structures, like the Walmart and Home Depot, sustained large areas of 

damage and collapse, some of which occurred in areas where people were located. Additionally, even 

though SJRMC’s patient care buildings did not collapse, their interiors were significantly damaged by 

winds and flying debris and this damage rendered them unusable. May 22, 2011, Joplin tornado fatalities 

were primarily located in buildings that were exposed to wind speeds within the EF–3 and EF–4 zones. 

NIST found no evidence that any fatalities occurred to individuals located below grade in this storm. 

4.6.3 Summary 

Across both indoor and outdoor settings, the majority of the impact–related fatalities (78 percent) and the 

sample of severe injuries (83 percent) occurred in areas where the tornado produced the strongest wind 

speeds (i.e., EF–3 or EF–4 wind speed zones). Additionally, 62 percent of fatalities, supported by 74 

percent of the sample of severe injuries, occurred in EF–4 zones. The wind speeds in EF–3 zones range 

from 136 mph to 165 mph and the wind speeds in EF–4 zones range from 166 mph to 200 mph. Only 8 

NIST NCSTAR 3, Joplin Tornado Investigation 323 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

percent of the fatalities and 6 percent of the sample of severe injuries occurred in wind speeds of less than 

110 mph. These data are shown below in Table 4–8. 

Table 4–8. Wind speeds associated with impact–related fatalities 

and severe injuries – all locations. 

Wind Speed Range 

(mph) 

Number of 

Fatalities Percentage 

Number of 

Injuries Percentage 

65–85 4 3 0 0 

86–110 8 5 2 6 

111–135 22 14 4 11 

136–165 25 16 3 9 

166–200 95 62 26 74 

Table shows that the majority of persons who suffered fatal or severe impact–related injuries in this 

tornado (approximately 77 percent of the fatalities and the sample of those severely injured) were located 

within 750 ft of the estimated center track of the tornado. “Within 750 ft” was chosen as the benchmark 

for this analysis because in this area the value for distance/RMW (i.e., distance from the tornado center178 

normalized by the average radius of maximum wind (about 0.16 miles, or 850 ft, or 260 m)) was less than 

one. Values for “distance/RMW” of less than or equal to one identify the areas in which individuals 

experienced the strongest winds.179 

Table 4–9. Impact–related fatalities and severe injuries by distance from 

the estimated tornado center track. 

Distance from 

Center (ft) Distance/RMW 

Number of 

Fatalities Percentage 

Number of 

Injuries Percentage 

100 0.12 14 9 5 14 

250 0.29 58 37 11 31 

500 0.59 31 20 8 23 

750 0.88 15 10 3 9 

1,000 1.18 9 6 4 11 

2,500 2.94 24 16 3 9 

5,280 6.21 3 2 1 3 

Key: RMW, radius of maximum wind. 

There were fatalities that occurred over 2,500 ft away from the estimated center track of the tornado. All 

three such fatalities (described earlier) occurred at 3877 East 27th Street in Joplin, outside in a drainage 

ditch. It is unclear if these individuals died from drowning or impact–related injuries. 

178 Distance from the tornado center as estimated by tree fall.
 179 RMW was smaller in the early stages of the tornado, but a "global tornado average" RMW was used here to make comparisons.
 

324 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4.7 

Chapter 4 

Overall, however, the majority of fatalities (and severe injuries) occurred in the areas that experienced the 

highest wind speeds. The information presented in the tables and in Fig. 4–40 suggests that the fatalities 

markedly increased at wind speeds of EF-3 or EF-4. The May 22, 2011, Joplin tornado demonstrated that 

being closer to the center of a strong to violent (EF–3 to EF–5) tornado is associated with experiencing 

higher wind speeds and a higher chance of fatal injury, even inside structures. The high fatality count 

observed in Joplin in these wind speed areas accentuates the need to consider ways of further protecting 

life–safety in tornado–prone regions. 

The environmental conditions to which the deceased were exposed during the tornado have been 

presented. The tornado produced winds that exceeded the design parameters used for many of the 

buildings within Joplin, and these winds posed risks for people regardless of whether they were indoors, 

in vehicles, or outdoors without any protection. Additionally, within the Joplin area, individuals had no 

access to public, FEMA–approved tornado shelters and very little access to underground locations or 

indoor storm shelters, either in homes or in commercial buildings. However, residents and visitors 

throughout the Joplin area received close to 20 min of warning lead time to find safety from the storm, as 

noted by the NWS service assessment of the tornado (NWS 2011). On some occasions in the past, people 

have evacuated areas predicted to be affected by impending tornadoes (Daley et al. 2005), making it 

imperative to understand the role that emergency communication and subsequent public response played 

in the casualties from this storm. 

The findings in this chapter reflect that a percentage (12.3 %) of the persons killed by this tornado were 

caught outside of buildings, and even outside of vehicles, when the storm hit. Additionally, some 

individuals interviewed by NIST, especially among those who were severely injured by the storm, found 

themselves actually driving into the path of the storm instead of away from it. Also, some fatalities and 

severe injuries occurred inside buildings where basements were available but the occupants did not use 

them for sheltering. 

In the following section, one additional question will be considered: Given the relatively generous 

warning lead time provided by Joplin’s emergency communication system, why did so many casualties 

occur, especially in places where safer locations were available? To answer this question, it was 

important to uncover the information that people received before the tornado struck, and the influence that 

this information had on risk perception and subsequent protective actions. 

THE INFLUENCE OF EMERGENCY COMMUNICATIONS AND PUBLIC 

RESPONSE ON CASUALTIES BOTH INSIDE AND OUTSIDE OF 

BUILDINGS 

As indicated in Sections 4.6.1 and 4.6.2, the fatally and severely injured, at times, did not reach places 

that could provide them with the best available protection from the storm. Some individuals were located 

outdoors or in vehicles when the tornado hit, with some even driving into the path of the storm. 

NIST NCSTAR 3, Joplin Tornado Investigation 325 
 

 

 

 

 

Chapter 4 

© 2011 GeoEye. Used with permission. Enhancements by NIST. 

Figure 4–40. Graphic showing the location of all 154 impact–related fatalities in relation to the EF wind speed zones (red =
 

EF–4, orange = EF–3, yellow = EF–2, green = EF–1, and blue = EF–0).
 

Note: ArcGIS placed SJRMC (hospital) further away than its actual distance from estimated center track of tornado. 

326 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

Additionally, there were instances in which individuals were located indoors, but refrained from taking 

refuge in the areas deemed by the NWS to be “safest,” for example, underground basements. Therefore, 

it is important to determine what influence emergency communications and public response had on the 

behaviors of these and other individuals who experienced the May 22, 2011, Joplin tornado. 

To answer this question, one must understand the motivations behind public response or, as sometimes 

was the case here, public non–response. NIST was unable to ascertain what emergency information the 

deceased had received and the subsequent motives or perspectives that guided their actions. Additionally, 

NIST did not have a complete sample of severely injured individuals, and even for the sample it did have, 

there was only limited data on the tornado–related information that these individuals received and the 

actions they took as a result. 

However, it is possible to determine the factors that influenced survivors (those injured or not injured) to 

decide against protective action. Although many interviewees eventually decided to take protective 

action and made it to a “safer place” (indoors, and in internal refuge areas), a majority of these survivors 

decided against protective action at some point in their decision–making process. If their rationales can 

be attributed as well to the deceased, and the authors of this report believe that this is a reasonable 

assumption, then we can begin to identify possible reasons why additional warning lead time did not 

necessarily lead to the protection of all individuals in this storm. 

NIST analyzed the behavior of a sample of people who experienced and survived the May 22, 2011, 

Joplin tornado and were subsequently interviewed by NIST for this investigation (n= 168 people). In 

support of this analysis, NIST also collected data from the over 100 eyewitness accounts found in 

newspapers and videos. The purpose of the analysis was to develop an evidence–based explanation for 

why individuals did not take protective action (or seek refuge) between 5:09 p.m. on May 22, 2011, when 

the first tornado warning was issued for (northern) Joplin or 5:11 p.m., when the first set of sirens 

sounded throughout the Joplin area, and the time when the tornado hit, which was at about 5:38 p.m. The 

explanation was also developed to identify the reasons why protective actions were eventually taken by 

those who took them. The interviews used in developing the explanation were from survivors who were 

responsible for their own protective decision–making, i.e., those individuals who, at some point during 

the warning period, had to decide for themselves what to do and when to do it (labeled here as “decision– 

makers”). “Decision–makers” included, for example, people in homes, in vehicles, outdoors, or traveling 

from one place to another before the storm hit. This analysis did not include interviewees who had been 

told by people in authority when and where to take shelter. This analysis also did not include managers or 

other employees whose role was to instruct others to take shelter (or not), since the sample contained too 

few individuals in such positions. 

For the development of this evidence–based explanation, 140 of the 168 survivors interviewed by NIST 

were identified as “decision–makers” and included in the analysis. The analysis focused on the 

information that these interviewees received before the storm, their interpretations of this information, 

and their subsequent behavioral responses related to seeking protection (or taking refuge in the “safest 

place” available). A discussion of the methods used to develop the evidence–based explanation is 

included in Appendix N. A model depicting the explanation is presented in Fig. 4–41. 

NIST NCSTAR 3, Joplin Tornado Investigation 327 
 

 

 

Chapter 4 

Figure 4–41. A model depicting protective–action decision–making 

in the May 22, 2011, Joplin tornado. 

328 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

4.7.1 Protection Is Unnecessary 

A majority of decision–makers decided, at some point before the tornado hit, that the act of seeking 

protection was not necessary. The evidence–based explanation presents two main reasons for this 

decision: not perceiving any general risk associated with this event and not perceiving personal risk 

associated with this event. In the first case, individuals who did not receive tornado alert– or warning– 

related cues on May 22, 2011, i.e., who were unaware that a tornado event was taking place, did not 

formulate any general risk associated with the event and thus, did not act to protect themselves. Of the 

140 survivors included in this analysis, 16 percent were unaware that a tornado event was taking place 

until a family member or friend called and/or the tornado was upon them. In the second case, individuals 

who were unable to confirm the existence of a tornado, either due to the receipt of conflicting or uncertain 

information and/or their pre–existing perspectives on tornadoes in general (formed prior to May 22), did 

not perceive any personal risk as a result of the weather that day. Of the 140 survivors, a majority of the 

sample (61 percent) were unable to confirm the existence of a tornadic event until they encountered direct 

visual or audible evidence of a tornado. Both branches of the model (depicted in Fig. 4–41) are described 

in the following sections. 

4.7.1.1 No General Risk Perceived 

There were decision–makers in the Joplin area who refrained from seeking protection because they did 

not perceive general risk associated with the event. These decision–makers (16 percent of the sample) 

were unaware that an impending tornado was approaching their location; i.e., they were unable to or did 

not, for various reasons, receive important information about the tornado. The 16 percent of decision– 

makers who fell into this category were distributed among three different awareness states that made the 

receipt of warning information difficult: asleep, awake with impaired hearing, and awake but 

disconnected from tornado–related emergency communications. In the following discussion, it is 

assumed that inaction (or decisions against seeking protection) by those who died or were severely 

injured could have occurred as a result of their being in similar awareness states. 

Unawareness of the event could have occurred as a result of hearing impairments. NIST spoke with 

interviewees who were unaware of the impending tornado due to some type of hearing loss (either 

permanent or temporary). For example, a couple in their late 80s was watching television before the 

storm hit, and do not recall receiving any information on the impending tornado. They were both hard of 

hearing, potentially making it difficult for them to hear outdoor sirens (which others claimed they could 

hear from indoors) as well as information provided via the television programming that they were already 

watching. Additionally, extended family members who would normally call and alert them of bad 

weather were out of town on the evening of May 22. That evening, the wife had noticed that it was 

getting dark outside. So she went to light candles near the front of the house when the following 

happened, according to the couple’s daughter: 

It just hit right then, and everything started flying, and [the husband] 

threw her [his wife] down in the hallway and just jumped on top of her 

and held onto the carpet as best he could, and the floorboards. He said 

when it was over this whole part of the roof was off. (NIST Interview 

20) 

NIST NCSTAR 3, Joplin Tornado Investigation 329 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

This couple was caught completely off–guard by this storm, and suffered minor injuries from being 

thrown around the house. 

Being hard–of–hearing or deaf made it more difficult for individuals to receive important information 

about the May 22, 2011, Joplin tornado. As mentioned in Sec. 4.3, in the Joplin area, weather alerts and 

warning information were disseminated via the following means: outdoor tornado sirens, television and 

radio broadcasts, NWRs, and opt–in mobile alerts (sent by local television stations). Joplin–Jasper 

County’s Reverse 9–1–1 system was not used on May 22, 2011. Unless the individual was actively 

watching a television channel on which weather information was visually provided, or had previously 

subscribed to mobile alerts (which was not prevalent among NIST–interviewed decision–makers), initial, 

pre–tornado alert information was likely not received by those with hearing impairments. This is due to 

the fact that outdoor sirens provided only audible content and the use of NWRs, including visually based 

NWRs for the hearing–impaired, was not prevalent in the Joplin area. 

Unawareness also could have occurred because individuals were sleeping at the time of the tornado, and 

did not receive important information regarding the May 22, 2011, Joplin tornado. NIST spoke with 

individuals who slept through the outdoor sirens, and because they were not alerted in any other ways 

(almost none had a working NWR), they neglected to tune into television, radio, or online resources for 

further information (NIST Interviews 41, 92, 102). Sleeping individuals were unaware of any risk 

associated with the event, and thus, did not consciously assign any risk to the impending tornado. At least 

one death attributed to the tornado was known to have been sleeping (in his apartment) when the storm 

hit. 

Being asleep, especially in the deepest stages of sleep, removes both audible and visual perception 

opportunities (Gwynne 2007). Unless sleeping residents received alerts sent directly to cell phones that 

were set to vibrate or ring loudly, or to NWRs that were tuned to a sufficient volume, waking would have 

proved difficult. Research into fire emergencies has highlighted the difficulty associated with waking 

individuals from sleep, and the importance of disseminating fire alarm signals at certain volume levels 

and using certain types of tone patterns (Bruck and Thomas 2007). Statistics have shown that tornadoes 

that occur at night are more deadly than those that occur during the day, potentially due to the fact that 

more individuals are sleeping during the former (Simmons and Sutter 2011). 

Finally, unawareness could have occurred because individuals were not connected to the necessary modes 

of emergency communication. In some cases, individuals were out–of–range from the city–wide tornado 

siren system, and/or simply did not hear the sirens from inside their homes. Even though the siren system 

was meant to alert individuals located outside of structures only, there was an overwhelming sense among 

the interviewees that Joplin–area residents located indoors (especially at home) relied on this technology 

to alert them as well. These decision–makers were also disconnected from other forms of tornado–related 

emergency communication, such as NWRs or opt–in subscription services that provide messages to 

mobile phones in the Joplin area. Joplin decision–makers (located at home before the storm hit) who 

owned an NWR (small percentage of the decision–makers) often admitted that their weather radio device 

was either not turned on, did not receive the signal, or did not go off (even though it should have) when 

storm warnings were assigned to their area. 

Decision–makers who were unaware of the event often relied on social networks to alert them to 

impending storms, if they received information at all. For example, NIST spoke with one deaf decision– 

maker who was located at home within the damage path of the storm. At home with her son, she was 

330 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

made aware of the storm by receiving a phone call from her mother, who told her to take cover (NIST 

Interview 69). Additionally, the individuals who were asleep as the tornado approached admitted that 

they were unaware of the impending tornado until a family member or friend woke them up (either in 

person or via a telephone call) (NIST Interviews 41, 92, 102). 

Some percentage of the decision–makers in this analysis who were unaware of the storm were older 

individuals (60 years old or above). It was shown earlier that a disproportionate number of older adults 

(aged 60 or above) died from this tornado (see Figures 4–18 and 4–19). It is plausible to suppose that 

some of these older decedents could have been hearing impaired, sleeping, and/or disconnected from 

tornado–related emergency communications when the event occurred, and/or without a social network, 

and as a result, died from this storm. When focused only on those individuals who died of impact–related 

causes (total 154), the data still showed that a disproportionately large number of older individuals (above 

the age of 60) died as a result of this storm (see Fig. 4–42). 

0 

2 

4 

6 

8 

10 

12 

14 

16 

18 

20 

0 to 9 10 to 19 20 to 29 30 to 39 40 to 49 50 to 59 60 to 69 70 to 79 80+ 

Fatalities per Thousand People (within the

Population) 

Age Range 

Tornado Fatality Rates by 10-Year Age Range (154 

Fatalities) 

Tornado Fatality Rates (Joplin Population) 

Tornado Fatality rates (Census Tract population) 

Source: U.S. Census Bureau 2010. 

Figure 4–42. Tornado fatality rates per thousand people within two populations: 

Population 1 – the entire population of Joplin and Population 2 – the population of the 

areas within Joplin most affected by the tornado (154 impact–related deaths) 

It is difficult to determine why older individuals were disproportionately represented among the deaths 

from the May 22, 2011, Joplin tornado. Even after removing those deaths that occurred in SJRMC and 

the two nursing homes, which were locations where one would expect older people to be overrepresented 

in comparison to their presence in the population, individuals 60 years old or older were still 

overrepresented among the remaining May 22, 2011, Joplin tornado fatalities (see Fig. 4–43 that includes 

the fatalities rates for those located and who died in single–family homes and apartments). 

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0 

2 

4 

6 

8 

10 

12 

14 

16 

18 

20 

0 to 9 10 to 19 20 to 29 30 to 39 40 to 49 50 to 59 60 to 69 70 to 79 80+ 

Fatalities per Thousand People (within the

Population) 

Age Range 

Tornado Fatality Rates by 10-Year Age Range (154 

Fatalities) 

Tornado Fatality Rates (Joplin Population) 

Tornado Fatality rates (Census Tract population) 

Residential Tornado Fatality rates (Census Tract 

population) 

Source: U.S. Census Bureau 2010. 

Figure 4–43. Tornado fatality rates (154 impact–related fatalities) and Residential tornado 

fatality rates (single–family homes and apartments, only) 

An issue is whether these older persons were fatally injured in internal refuge locations (i.e., they were 

aware of the storm and died even after taking protective actions) or whether they were caught off–guard 

by the storm and could not reach a safer location in time. Unfortunately, information on refuge locations 

could not be obtained for all of the 154 impact–related deaths, possibly because many of the older adults 

who died in residential locations were alone at the time the tornado hit. Also, there is no way to 

determine if the older decedents suffered from hearing impairments or any other illnesses or physical 

limitations that would hinder their ability to take shelter in a timely manner or their ability to physically 

endure the types of injuries that EF–3 and EF–4 wind and debris environments can inflict. 

4.7.1.2 No Personal Risk Perceived (“It Will Not Happen to Me”)

The second branch of the model (Fig. 4–41) shows that there were decision–makers who decided against 

seeking protection within the Joplin area because they did not perceive personal risk. These decision– 

makers (61 percent of the sample) were unable to confirm the existence of a tornado and thereby to 

perceive personal risk, because they received conflicting or uncertain information early on in the warning 

process, which was further complicated by their own pre–existing perspectives on tornadoes in general 

(formed prior to May 22, 2011). 

When initial information was given to decision–makers on May 22, 2011, around 5:09 p.m., including the 

sirens that sounded at 5:11 p.m., there was little information available that would help confirm the risk of 

a tornado threatening the large portion of Joplin that was actually hit around 5:41 p.m. Any warning 

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information provided to individuals around 5:09 p.m. (until 5:17 p.m.) related to a storm that weather 

forecasters were tracking to the north of Joplin, which was heading toward Webb City, Missouri, or Carl 

Junction, Missouri (Tornado Warning Polygon 30). A Joplin native remembered that 

the announcer and the weatherman that came on the TV seemed to say 

the track was, you know, mainly north of town. It wasn't going to be a 

bother for where I was at towards the south part of town. So, I continued 

to sit there on the front porch and enjoy the cool air that was, you know, 

for the day. (NIST Interview 58) 

Another interviewee tuned his television to the Weather Channel to view the forecast after hearing the 

sirens sound. According to him, the storm “looked like it was even way up north, like Pittsburg. I said, 

‘That’s not gonna come down and get us.’ So I just kind of ate my food there and was watching [the 

television]” (NIST Interview 94). After hearing this information and based upon the perceived tendency 

for storms to track toward the northeast only, interviewees formulated that they were not at risk. 

Around this same time, individuals were offered very little in the way of environmental cues of an 

impending storm, also making it difficult to confirm the tornado risk. People looked outside, to the sky, 

for clues that a tornado was coming and saw only clouds that did not look as menacing as what would 

accompany a tornado. An interviewee recalled his actions at home that evening: 

The tornado sirens went off once, we walked outside and you couldn’t 

really, didn’t really see nothing then, and we went back in and finished 

eating. (NIST Interview 108) 

The decision had become as simple as that—if there was nothing in the sky to worry about, then it was 

appropriate to return to your previous pursuits until something else caught your attention. Some people 

continued to monitor the weather reports, while others resumed activities unrelated to the weather. 

As the first set of sirens stopped and time progressed, interviewees who continued to monitor the weather 

via television or radio (or Internet sources) still did not perceive firm confirmation of an impending storm 

likely to affect them. First, the NWS issued a tornado warning at 5:17 p.m. for the storm that eventually 

hit Joplin; however, the outdoor siren system was not reactivated at 5:17 p.m., likely because Joplin’s 

emergency manager had already sounded the sirens 6 min earlier (for the northeastern Joplin storm that 

did not materialize). Additionally, interviewees who had been tuned into the news outlets at 5:17 p.m. 

primarily reported that the media continued to discuss a storm that was to the north of Joplin. Decision– 

makers recalled hearing that the storm would miss them, since it was “going around Galena” (NIST 

Interview 23), passing to the north (NIST Interview 33), or simply moving away from them (NIST 

Interview 36). Others recalled announcers continually discussing a tornado between Carl Junction and 

Webb City (NIST Interview 60) or news of a tornado that had hit a small town in Kansas (NIST 

Interviews 47, 58). Meanwhile, broadcasters for a news–based radio station disseminated via several 

channels throughout the Joplin area were discussing the potential for winds, power outages, and large– 

sized hail, with no confirmed reports of a tornado on the ground until 5:40:44 p.m., 3 min after the 

tornado entered Joplin, when the emergency manager for Joplin–Jasper County was contacted by the 

station and interviewed about the location of the storm. This broadcast then informed listeners that a 

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tornado was on the ground at approximately 7th Street and Schifferdecker Avenue180 or 7th Street and 

Range Line Road, and it was pushing to the east or slightly southeast; however, both locations turned out 

to be inaccurate regarding the tornado’s path (KZRG 2011). Interviewees who had decided not to 

continue monitoring the weather reports (e.g., NIST Interview 27) simply turned the television or radio 

completely off or tuned into another station that was not necessarily issuing weather updates. 

For most of the interviewees, certain storm–related cues eventually captured their attention again. When 

television and radio stations mentioned that a tornado was on the ground, people took notice. 

Interviewees remembered hearing information about a tornado at Iron Gates, which was located in Joplin. 

One television station, equipped with a tower cam, was remembered for showing video footage of the 

imminent tornado (which looked more like a wall of debris than a funnel) and the damage it was 

producing on its way to Joplin. News announcers on this station pleaded with listeners to “Take cover 

now!” (KSNF 2011). But by this time, the tornado was minutes or even seconds away from listeners in 

Joplin. 

For those looking to confirm their personal risk by seeing an approaching funnel–shaped cloud, the 

opportunity never came. The tornado was wrapped in rain and a wall of debris, and was made even more 

difficult to decipher by Joplin’s city–based landscape. As a result, there were individuals caught in their 

cars driving into the storm, or outside of their cars, as the tornado bore down upon them. It was not until 

the wind was whipping so hard and the debris was so thick that they could not see, that those driving 

actually stopped and waited out the storm inside their vehicles. Before this moment, they were not sure 

that a tornado was actually going to hit them. 

There were also individuals located in their homes, but outside of the internal sheltering locations 

suggested as safer by the NWS. Very little information was available with which these people could 

confirm imminent risk from a tornado, until people heard what was characterized by many as the sound of 

a freight train increasing in volume, or saw the wind bending large trees to the ground, for example. 

Unfortunately for some, they had waited too long to take shelter in a safer place. The tornado was already 

upon them, ripping the structure apart, before they had time to reach an internal or underground shelter, if 

one were available to them. 

This inability to confirm personal risk in a timely manner on May 22, 2011, was exacerbated by Joplin– 

area residents’ perspectives on tornadoes in general. When asked about their views on the possibility of 

severe storms in Joplin, decision–makers in the 140–person sample (and even other NIST interviewees) 

generally did not believe that tornadoes in Joplin were something that they would witness during their 

lifetimes. 

One factor behind these views was a public perception, which was pervasive among the decision–makers, 

that false alarms were common in Joplin. As mentioned earlier in the chapter, the false–alarm rate for 

NWS–issued tornado warnings for the City of Joplin had increased to 92 percent during the period from 

2007 to 2011, and interviewees seemed to have noticed this trend. One individual described his 

perspective on storm warnings as follows: 

180 Both addresses (7th Street and Schifferdecker Avenue and 7th Street and Range Line Road) were located north of the tornado’s

estimated path. 

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I grew up in Arkansas and spent a lot of time in Oklahoma, and then 

Missouri in this area. So, tornado watches are common. But, tornadoes 

don’t always strike, and they’re usually small. So, the chances of it 

truthfully hitting are pretty slim. (NIST Interview 10) 

Decision–makers seemed to blame the outdoor siren system for overwarning as well, even though the 

sirens sounded only once per year, on average, for wind–related events. An interviewee who had lived in 

Joplin for over 40 years dismissed the credibility of the 5:11 p.m. siren almost immediately on May 22, 

2011, since she had often heard sirens in the past that were not followed by severe storms, winds, or 

tornadoes. She commented as follows: 

But the sirens have gone off a lot and they'll go off—they'll stay on for 

two to five minutes and then it's over and, you know, so you—hear sirens 

a lot but they never really amounted to much of a storm, so you kinda 

took the warnings lightly, I guess you could say. (NIST Interview 84) 

Similarly, another Joplin native noted that after seeing only clouds in the sky, she did not think much of 

the sirens; they go off so much, she said, that she did not take them seriously on May 22, 2011 (NIST 

Interview 102). Overall, interviewees acknowledged that the “zoned” Joplin sirens are required to sound 

for an area larger than may be affected by a storm. However, the prevailing perception was that the 

system lacked credibility. 

Even if a tornado did materialize, most interviewees erroneously believed that they would be safe inside 

the city limits of Joplin. Residents were confident that they would be protected from severe storms and 

tornado damage, and believed that “it cannot happen to us” based upon tornado tracking beliefs or myths. 

Many believed that tornadoes only track to the northeast, not due east and certainly not south. So, if a 

tornado was located north of the City of Joplin, as was the case for Tornado Warning Polygon 30, issued 

around the same time as the first sirens sounded, many were quick to believe that they were safe from that 

particular storm. Additionally, interviewees believed that severe storms always went around Joplin to the 

north or the south, creating a mythical “bubble” around their city that protected them from harm. One 

Joplin resident described the bubble phenomenon as a “magic little V that [the tornado] splits off and goes 

into one of these directions [i.e., north or south of the city]” (NIST Interview 119). Individuals also relied 

on the geography of the region to keep the storms away. One interviewee acknowledged that the storm 

that hit Joplin on May 22, 2011 was a very large, unique storm. He supported his belief that a regular– 

sized storm would have never hit Joplin with the following reasoning: 

The geography of this area is as such that I like our chances. There's a 

lot of rolling hills and a lot of natural barriers and obstacles for a tornado, 

if it's on the ground, for it to follow. I'm pretty confident. (NIST 

Interview 5) 

Others looked to the rivers around the Joplin area to provide barriers to tornadoes. 

Before May 22, 2011, the thought of tornadoes produced little anxiety among area residents. The 

occurrence of tornadoes had been perceived as a habitual event. Joplin residents had an overwhelming 

sense of being “around tornadoes several, several, several times” in their lives (NIST Interview 109). 

However, the difference between being around tornadoes and being in a tornado was rarely 

acknowledged. Very few interviewees had actually experienced a tornado that damaged their own city or 

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town, especially their own houses or commonly frequented businesses. Additionally, tornadoes that had 

occurred were not perceived as having been very large or damaging. Although nearly all of the local 

people interviewed by NIST (158 out of a total of 165) identified their homes as being within a tornado– 

prone region, tornadoes were often described benignly as storms that simply drop from the sky, with little 

notice, and bounce up and down the plains (NIST Interviews 61, 109). One tornado survivor described 

his pre–May 22 attitude about storms, which was based on his experiences as a storm watcher: 

I was very flippant about the whole thing. I really was 'cause I grew up 

here. I know the activity of tornadoes. I know how they—they're cute. 

They hit one house and they jump over and hit the next one. And they're 

just adorable little funnel things that you see in the distance. (NIST 

Interview 85) 

Also, some interviewees expressed their confusion regarding the tornado siren protocol. As mentioned 

earlier, the Joplin–Jasper County siren system was activated when any one of the following criteria were 

met: any kind of tornadic activity or warning, or winds of at least 75 mph. On May 22, 2011, some 

interviewees were confused about how long the sirens should sound and the reasons why the sirens 

stopped after 3 min. Additionally, Joplin survivors were unsure why the second siren had been initiated, 

since this had been perceived by many as never happening in the past. Their interpretations of the second 

siren ranged from it being a warning for a situation that was more dangerous than before to an “all clear” 

from danger. 

It was difficult for decision–makers to perceive personal risk from an emergency communication system 

that they perceived as providing conflicting or unclear messages or messages with questionable 

credibility, especially for people with pre–existing perceptions of emergency communications or 

tornadoes and/or confusion about emergency communication protocols. In response, decision–makers 

decided against taking protection, often continuing on with daily activities as if there was little or no 

impending tornado threat. Until cues intensified, the personal risk was not perceived as being high 

enough to prompt protective action, which in turn, influenced individuals’ decisions to drive their vehicles 

through town, remain outdoors until they were in winds in excess of 160 mph, or delay seeking protection 

for so long that the tornado hit before safer locations could be reached. 

4.7.2 Protective Action Is Necessary 

Eventually, almost all decision–makers decided that protection was necessary at some point before the 

tornado hit their location. However, just because survivors made the decision to take protective action did 

not mean that they reached their optimal location before the tornado reached them. For example, some 

individuals were located in their cars, and simply pulled over to ride out the storm. There were two 

reasons why individuals decided that protection was necessary in the Joplin storm. The first was that 

confirmation of the tornado was achieved after the initial warnings were provided (at 5:09 p.m. or 5:11 

p.m.). The second was that personal risk was perceived; however, this occurred as the tornado was 

approaching. Both reasons are discussed in the following sections. 

4.7.2.1 Confirmation Is Achieved After Initial Warnings 

There is one additional branch on the model (Fig. 4–41) that has not yet been described. For 17 percent 

of the decision–makers, confirmation of the tornado was achieved when they received the initial set of 

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warning information (i.e., the first set of sirens and/or the news about a northern storm). These 

individuals took action to protect themselves and their families based upon the same types of information 

that a majority of individuals (in this sample) used to decide against action. 

The main reason identified for taking “early action” in this tornado was the nature of decision–makers’ 

personalities and/or pre–existing risk perceptions associated with tornadoes. Two types of personalities 

are identified here: “risk–averse” decision–makers and “hypervigilant” decision–makers. Risk–averse 

decision–makers claimed to have sought protection every time they had heard the sirens activated before 

May 22, 2011. The act of taking refuge had become a habit for them during tornado season, and 

therefore, based on past experiences, they took refuge as soon as the sirens sounded on May 22. All 

individuals categorized as “risk averse” (3 out of 140) had a basement available to them; therefore, taking 

refuge early was not a difficult task and they were able to continue to monitor the situation as time 

progressed, via television, radio, Internet–based technology, or small basement windows. It was not so 

much that this group felt at risk from this storm, but more that they were habitually risk averse in 

tornado–related situations, taking the safest route every time (or almost every time) the sirens sounded. 

Decision–makers categorized as “hypervigilant” (7 out of 140) described themselves as generally fearful 

of tornadoes, although none had actually been through a tornado before. These individuals had been 

monitoring the weather throughout most of the day on May 22, starting hours before the sirens sounded. 

Whereas other decision–makers perceived the outdoor siren (or other initial alert) as their first actual 

tornado warning, “hypervigilant” decision–makers perceived the siren or other initial alerts (even about 

the northern storm) as confirmation that something serious was actually taking place, which prompted 

them to take immediate protective action. 

Additional decision–makers who achieved confirmation after the receipt of the initial set of warning 

information recalled that they were tuned into a media source that confirmed that a storm was heading 

their way. These individuals perceived risk based upon information that they received, earlier on, from 

media outlets. Although NIST reached out in March 2013 to all media outlets serving the Joplin area 

about their broadcasts before and during the storm, including the hours before the storm hit, almost all 

media outlets no longer retained recordings of what they had broadcast during this period. Two television 

stations (KOAM–TV and KSNF) provided video recordings of their broadcasts from no more than 5 min 

before the tornado hit, one of which provided the “tornado cam” and pleaded with listeners to “Take 

cover now!” as the tornado bore down upon the city. The other station, while providing information 

about the storm’s path, was much less urgent and intense in warning people to take cover. Additionally, 

Zimmer radio provided its tornado coverage to NIST in 1–hour increments, from 4 p.m. to 5 p.m., 5 p.m. 

to 6 p.m., and 6 p.m. to 7 p.m. Instead of providing confirming evidence early on in the warning timeline, 

which can be difficult in tornadoes, these limited datasets support the observation discussed earlier in Sec. 

4.7.1.2, that little information confirming the existence of a tornado (on the ground) was provided to 

viewing or listening audiences until the tornado was minutes or even seconds away. Inaccurate 

information about the tornado’s location and/or expected path was also provided by multiple media 

sources before the storm hit. 

4.7.2.2 Personal Risk Is Perceived 

The majority of decision–makers, who eventually decided that protection was necessary, did so only after 

receiving intense cues from the environment (shown as the lower branch in Fig. 4–41). Intense cues were 

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those visibly or audibly disseminated by the tornado. Actually seeing the massive debris wall heading 

straight for them or hearing the sound of a freight train caused Joplin survivors to perceive risk and that 

they were potentially in trouble. High–intensity cues also included seeing large trees swirling or laying 

down on the ground, seeing cars or other heavy objects lift or fly off of the ground, and hearing 

information about the tornado in an urgent tone (i.e., the newscaster who urgently prompted people to 

“Take cover now!”). It was at this point when they realized that protection was necessary if they wanted 

to escape this tornado unharmed. Seeing or hearing these cues prompted individuals to take shelter in 

various locations in buildings, in vehicles, or outdoors. Among these individuals, the intense cues 

triggered cognitions about risk and danger to themselves, their friends, and family members. In some 

cases, the cues were so severe that individuals who were already located in their basements moved to an 

internal refuge area (closet or bathroom) within their basement. 

Because the majority of decision–makers waited until the last moment to take protective action, their 

sheltering options were often limited and suboptimal. In homes, even though Joplin survivors frequently 

had access to crawl space refuge areas, they rarely considered these spaces as viable options for this storm 

due mainly to the time required to access them. This forced individuals without basements or tornado 

shelters to utilize aboveground bathrooms, closets, and laundry rooms for safety. Additionally, last– 

minute decisions caused drivers in Joplin to simply pull over and face the massive storm—which often 

meant getting hammered with debris or even lifted up into the storm (inside or outside of their vehicle), 

only to crash down again. Some last–minute decision–makers were caught outside of houses and 

businesses, where they were forced to fight for their lives by holding onto the structure. And, even in 

some businesses, last–minute decisions left people running to shelter locations as the tornado ripped their 

building apart. 

4.7.2.3 Other Actions During Decision Making 

Although not featured in Fig. 4–41, some Joplin survivors engaged in preparatory actions and helping 

behaviors in lieu of taking immediate refuge from the storm. Many Joplin survivors located at home 

prepared their shelter areas, themselves/family members, or their pets in some way before the storm hit. 

It was difficult to identify the factors that led individuals to prepare before sheltering. Individuals who 

skipped preparation activities decided to take protective action at the moment when the tornado was 

hitting their house, leaving them with little time to perform preparatory actions even if they had desired to 

do so. Additionally, a group of Joplin survivors took time to instruct others—loved ones, customers, 

employees, hospital patients or visitors, or others—to take shelter after they had decided to do so. These 

individuals often felt in some way responsible for the people around them. 

4.7.3 Other Important Factors Related to Casualties 

Studies of previous tornadoes have identified risk factors for injuries and deaths due to tornadoes in the 

United States. Simmons and Sutter (2011) performed an extensive regression analysis of tornadoes that 

occurred in the United States from 1950 to 2007 to understand the factors that contributed to injuries and 

fatalities. Their results indicated that risks of fatalities and injuries were heightened when: 

	 Tornadoes occurred at night, likely because residents were asleep at this time and less likely to 

receive warnings. 

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	 Tornadoes occurred during fall or winter months, likely due to a lulling effect during these 

seasons and individuals’ failure to recognize the potential for off–season tornadoes. 

	 People in affected areas were in manufactured homes during the tornado. The authors found a 

disproportionate share of fatalities in manufactured homes during less–intense tornadoes (F–1, 

F–2, and F–3) versus fatalities in permanent homes, which generally occurred in more violent 

tornadoes. 

	 The affected area was located in the southeastern part of the United States. The annual tornado 

rate was found to be negatively correlated with the State casualty index (i.e., rates of fatalities and 

injuries per million residents), possibly because those States accustomed to tornado events are 

more likely to be prepared (and thus, less likely to experience casualties). Additionally, the 

coefficient of variation for the annual tornado count, i.e., how consistent tornado event numbers 

are from year to year, was positively correlated with the State casualty index, possibly meaning 

that States that are accustomed to experiencing consistent numbers of tornadoes are more likely to 

be prepared. Finally, the authors found that the percentage of a State’s land covered by forest is 

positively correlated with the State’s casualty index, suggesting that casualties are higher in 

places where it is more difficult to see approaching tornadoes. 

None of these factors was operative in the May 22, 2011, Joplin tornado. Therefore, it is conceivable that 

the death and injury toll resulting from the May 22, 2011, Joplin tornado could have been even higher if 

the tornado had occurred, for example, at night and/or in the fall or winter months. The toll also could 

have been greater if the tornado had targeted other areas within Joplin or beyond that contained mobile 

home neighborhoods. 

Studies have also shown that an additional factor, which was a potential factor in the May 22, 2011, 

Joplin tornado, has contributed to injuries and fatalities in previous tornadoes (Simmons and Sutter 2011). 

That factor is warning lead time (or the time between warning dissemination and tornado touchdown). 

Simmons and Sutter found that a warning lead time of 6 min to 10 min provided the largest reduction in 

expected fatalities when compared with an unwarned tornado. Overall, warnings with lead times up to 15 

min reduce casualties; however, the authors found no additional benefit for warning lead times of 16 min 

or more. 

In the May 22, 2011, Joplin tornado, warning lead times of greater than 17 min occurred. However, the 

effectiveness of this relatively long lead time appears to have been offset by a number of factors, 

including the distraction and confusion effected by the northern storm, the failure of the community– 

based information sources to provide accurate up–to–the minute information, and the lack of early 

environmental cues, which lead to inaction of residents until the very last minute. This analysis has shown 

that the wind environment and issues with building performance were also significant causes of casualties 

from this storm. 

CHAPTER SUMMARY 

The objective of this chapter is to describe the pattern, locations, and causes of the fatalities and injuries 

attributed to this tornado, and to examine the associated emergency communications and public response. 

This chapter provides an understanding of the behavior of individuals exposed to the May 22, 2011, 

NIST NCSTAR 3, Joplin Tornado Investigation 339 

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Chapter 4 

Joplin tornado, and of the factors that influenced survival or death, including the protective actions of 

affected persons, the performance of affected buildings, and the environmental conditions that the tornado 

brought to these people and buildings. More attention is given to understanding the deceased population 

than the injured population due to the sheer number of injuries caused by this storm and the limited 

information available to NIST on the injured population. The purpose of this portion of the investigation 

was to identify recommendations relating to emergency communication, building and shelter 

performance, and public training or education that can improve public safety in future tornadoes. 

A total of 161 deaths and more than 1,000 injuries have been attributed to the May 22, 2011, Joplin 

tornado, a storm that damaged an area with an estimated population of 20,820. To understand the causes 

of the tragic death toll, NIST interviewed family and friends of the deceased and analyzed information 

obtained through official death records, obituaries, publications about the storm, and public forums 

honoring the dead. 

This mortality research revealed that of the 161 deaths resulting from this tornado, 155 (96 percent) were 

caused by impact–related factors (i.e., multiple blunt–force trauma to the body). Others were caused by 

stress–induced heart attacks, pneumonia, and lightning. Further analysis showed that of the 155 impact– 

related deaths, 135 (87 percent) were of persons known to have been located indoors during the tornado. 

The structures in which people died included both residential (59 percent) and non–residential (41 

percent) buildings. 

It was important to understand why so many fatalities occurred inside of the potentially protective 

environments provided by buildings. NIST found that virtually all of the buildings in which the 135 

indoor, impact–related fatalities occurred experienced maximum estimated winds associated with EF–3 or 

stronger tornadoes, which exceeded the code-level wind design condition for buildings in the Joplin area. 

NIST also found that the hospital towers at SJRMC did not provide life–safety for all occupants, even 

though the tower themselves did not collapse. A total of 12 impact–related fatalities occurred in the 

hospital; 4 of these victims were ICU patients. 

Public response to the impending May 22, 2011, Joplin tornado was found to have been overwhelmingly 

delayed or incomplete. For the most part, it was not until individuals received high–intensity cues, such 

as hearing or seeing the tornado approach or witnessing the urgency with which others sought protection, 

that they took actions to protect themselves. In many cases, this delay resulted in truncated protective 

actions and suboptimal sheltering, as was evidenced by the fatalities that occurred outdoors and in 

vehicles, and by the deaths of persons who had been rushing to obtain safer refuge at the moment when 

the tornado hit. An analysis of the behavior of May 22, 2011, Joplin tornado survivors (who delayed their 

response to the storm or did not take shelter at all before the storm hit) identified two factors that 

contributed to the delayed public response: (1) a lack of awareness of the tornado, and (2) an inability to 

perceive personal risk due to one or more of the following: the receipt of conflicting or uncertain 

information about the tornado, pre–existing beliefs about tornadoes or Joplin’s invulnerability to 

tornadoes, and distrust of or confusion about Joplin’s emergency communication system. 

Conflicting and uncertain information was prevalent in this storm. On May 22, 2011, two official tornado 

warnings were issued within a span of 10 min, the first pertaining to only part of Joplin and the second to 

the entire city. After the first official warning, the tornado sirens were sounded but no tornado occurred. 

After the second official warning, 21 min elapsed before the sirens were sounded again as the tornado 

340 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 4 

entered the city. While the outdoor siren system frequently prompted Joplin residents and visitors to seek 

further information on May 22, 2011 (i.e., acting as an alert system rather than a warning system), the 

multiplicity of information sources, and the conflicting information provided by these sources, added to 

the public’s confusion about the true hazard. Additionally, other means of alerting individuals about the 

storm (i.e., radio, television, EAS, or weather radio) were less effective in prompting response, and the 

Joplin–Jasper County Reverse 9–1–1 system was not used on May 22, 2011. 

Pre–existing beliefs that Joplin was immune to a direct tornado strike and distrust of or confusion about 

emergency communications were also prevalent in this storm. NIST found evidence of high false–alarm 

rates in Joplin for NWS–issued tornado warnings, but not for Joplin’s outdoor siren system (which had an 

average activation rate of once per year)—even though citizens perceived high false–alarm rates for both 

warning sources. NIST found that the roughly 30–square–mile City of Joplin experienced only one 

tornado rated EF–2 or greater since 1950, while areas surrounding Joplin (within an 80–mile radius) 

experienced many more, circumstances that may have bolstered local beliefs about the city’s immunity to 

direct tornado strikes. Finally, NIST found that, across the United States, there was no standard method 

for sounding outdoor public siren systems, resulting in variations in siren usage, activation procedures, 

and sounding patterns among communities. This lack of standardization could have led to confusion 

about Joplin’s emergency communication system on May 22, 2011, which was exacerbated by the rare 

occurrence of two siren activations (at 5:11 p.m. and 5:38 p.m.) during the same evening. 

Other factors possibly related to the May 22, 2011, Joplin tornado deaths were also identified. One was 

the lack of basements or underground spaces in the Joplin area. NIST found that no fatalities occurred in 

single–family homes demolished by the tornado in which people took refuge in basements. Additionally, 

NIST found no evidence that any of the Joplin fatalities occurred underground. Another factor that 

emerged was age. NIST found that a disproportionate number of people aged 60 years or older died or 

were injured as a result of this tornado, even after removing all hospital and nursing home deaths. 

Potential explanations for this finding include limited information flow to these individuals, a lack of 

supportive social networks among this group, and greater physical frailty among older individuals. 

Finally, although this is not identified as a contributor to deaths or injury in the tornado in this report, the 

authors would be remiss not to mention the many examples of altruistic behavior identified by survivors 

of this storm. There were instances identified where individuals laid their own bodies over loved ones to 

provide shelter from the storm, and in some cases (e.g., the Joplin Elks Lodge), those who were protected 

survived to tell about their experiences. Disasters in the past have been shown to bring out “the best” in 

people, and the stories told to NIST by the May 22, 2011, Joplin tornado survivors are no different. The 

survivors, themselves, became the first responders, both before and after the storm hit Joplin, MO. 

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4.9 

Chapter 4 

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Younker, Emily. 2011b. Employee recounts tornado inside destroyed Home Depot. Joplin Globe. May 

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Chapter 5 

FINDINGS AND RECOMMENDATIONS 

5.1 PRINCIPAL FINDINGS 

The National Institute of Standards and Technology (NIST) developed findings based upon information 

collected during and after the initial reconnaissance, interviews conducted with survivors, and data 

analyses related to environmental conditions, building performance, and emergency response and 

communications activities. These findings are enumerated in Sections 5.1.2 through 5.1.4, following the 

contextual observations presented in Sec. 5.1.1. 

5.1.1 Context for Findings 

	 National model building codes, standards, and practices seek to achieve life safety for the 

hazards that are considered in design. While these considerations include hurricane and 

nontornadic wind, flood, snow, rain, earthquake, and ice loads, they do not include tornado 

hazards (loads due to wind speeds that significantly exceed code–compliant design wind 

speed and impacts of wind–borne debris). Thus, buildings and other structures are not 

designed for tornado hazards currently. The sole exceptions are safety–related structures in 

nuclear power plants and storm shelters or safe rooms. 

	 There are currently two tornado hazard maps prescribing different tornado hazard 

regionalization and associated wind speeds for the contiguous United States: 

	 The ANSI/ANS 2.3 (2011), NRC/RG 1.76 (2007), and DOE 1020 (2002) map for 

designing nuclear–related facilities (three regions, 230 mph maximum wind speed); and 

	 The ICC 500 (2008), FEMA 320 (2008), and FEMA 361 (2008) map for designing 

shelters and safe rooms (four regions, 250 mph maximum wind speed). 

	 Current building codes and standards prohibit the use of aggregate roof surfacing materials or 

ballast for hurricane–prone regions,181 but allow their use in other regions based on mean roof 

height and exposure category. For the City of Joplin, the building code182 at the time of the 

May 22, 2011 Joplin tornado allowed aggregate roof ballast for buildings with a mean roof 

height of less than 110 ft. 

	 In the State of Missouri, the adoption and enforcement of building codes are prerogatives of 

local government. The City of Joplin’s building department has a long history of code 

181 Defined in ASCE/SEI Standard 7–10 Minimum Design Loads for Buildings and Other Structures as: Areas vulnerable to 

hurricanes; in the United States and its territories defined as (1) The U.S. Atlantic Ocean and Gulf of Mexico coasts where the 

basic wind speed for Risk Category II buildings is greater than 115 mph, and (2) Hawaii, Puerto Rico, Guam, Virgin Islands, and 

American Samoa. 

182 IBC 2006 

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Chapter 5 

adoptions, and typically has adopted the latest national model building codes shortly after 

they have been issued. 

	 Like most other municipalities in tornado–prone areas and the contemporaneous model 

building codes, the City of Joplin does not mandate the construction of shelters or safe rooms 

in residential or non–residential facilities. Additionally, the City did not own or operate any 

public storm shelters. The lack of public shelters and requirements for safe rooms in 

residential or non–residential facilities meant that many residents in the area affected by the 

May 22, 2011, Joplin tornado, particularly those who were living in multi–family residential 

buildings or older nursing homes, did not have access to such sheltering options during this 

tornado. 

5.1.2	 Findings Related to Tornado Hazard Characteristics and Associated Wind 

Field 

5.1.2.1	 Measurements of the Near–Surface Wind Field in Tornadoes 

Finding 1—

Current operational weather radar technology is incapable of determining tornado occurrence and 

intensity at heights above the ground that are relevant to structural engineering design (i.e. at the heights 

of buildings). For example, because the nearest operational radars to Joplin were more than 60 miles 

away they could only measure conditions at altitudes starting at 5000 ft. 

Finding 2—

Reliable direct measurement of wind speed in tornadoes, especially the most intense tornadoes, is lacking 

or non–existent. Wind speed measurements related, but not directly, to the May 22, 2011, Joplin tornado 

were limited to one location well outside the tornado damage path. The difficulty in measuring tornado 

intensity discussed in both Findings 1 and 2 have been noted in previous tornado research. 

Finding 3—

NIST estimated the maximum wind speeds in the May 22, 2011, Joplin tornado to be 175 mph with up to 

25 percent of uncertainty. With uncertainty, the upper bound of the estimated maximum wind speed in the 

Joplin tornado was 210 mph. The uncertainty was due to the use of indirect wind speed estimation 

methods (i.e., tree–fall analysis, EF Scale). Due to the lack of radar and direct wind speed 

measurements, indirect methods served as the sole estimators of wind speeds in the May 22, 2011, Joplin 

tornado. While existing indirect methods cannot be used to unambiguously determine wind speeds that 

can be used in structural design, the remaining findings in this study are not sensitive to the level of 

uncertainty in this methodology. 

Finding 4—

The estimated duration and spatial extent of damaging winds in the May 22, 2011, Joplin tornado were 

significantly greater than those expected based on those used in current tornado hazard models. This 

finding is consistent with other studies that have estimated wind fields in actual tornadoes. For example, 

wind speeds in the Joplin tornado that exceeded those associated with EF–3 accounted for approximately 

twice the spatial area expected based on modeled estimations for an EF–5 tornado. 

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5.1.2.2	 Assessment of Tornado Climatology, Hazard, and Risk for Structural Design 

Finding 5—

The probability of occurrence and subsequent risk of tornadoes is significantly underestimated by point– 

based methodology. It was shown that actual damage in Joplin and other communities affected by 

damaging tornadoes was greater than predicted using point–based methodology. 

Finding 6—

Tornadoes rated EF–3 or lower have accounted for approximately 96 percent of all U.S. tornadoes 

between 1950 and 2011, over one–third (36 percent) of the approximately 5,600 tornado–related fatalities 

over the same period, and about 80 percent of the $25 billion183 in estimated property losses incurred due 

to tornadoes between 1996 and 2011. Even in a tornado with intensity greater than EF–3, the wind 

speeds in the majority of the affected area are equivalent to or less than the maximum wind speeds 

associated with EF–3 tornadoes. In the case of the Joplin tornado, approximately 40 percent of the 

fatalities and as much as 90 percent of the tornado area were associated with EF–3 or lower wind speeds. 

5.1.2.3	 Limitations of the Enhanced Fujita (EF) Scale 

Finding 7—

The Enhanced Fujita scale lacks adequate damage indicators (DI’s) and corresponding degrees of damage 

(DOD’s) for distinguishing among the most intense tornado events. The lack of DI’s and DOD’s and 

overall nature of the EF–scale requires subjective, non–quantitative assessment of tornado damage. 

5.1.3	 Findings Related to the Response of Residential, Commercial, and Critical 

Buildings, Including the Performance of Designated Safe Areas and of 

Lifelines Pertaining to the Continuity of Building Operations 

5.1.3.1	 Building Performance 

Finding 8—

Buildings are not designed to withstand tornado hazards and there are no building code requirements for 

tornado–resistant design. Most buildings in the area damaged by the May 22, 2011, Joplin tornado were 

subjected to wind speeds close to or above the speeds that would be expected to cause collapse of or 

major damage to structures designed to the non–tornadic wind design requirements of the building codes 

applicable to them. Wind–borne debris, which contributed significantly to building damage in Joplin, 

also is not considered as a hazard in building design. 

Finding 9—

Regardless of construction type, neither affected residential nor non–residential buildings were able to 

provide life–safety protection in the May 22, 2011, Joplin tornado. Of the 161 fatalities, 135 (or 83.8 

percent) were related to building failure. Of these building failure–related fatalities, 74 (52.5 percent) 

occurred in residential buildings. Of the buildings that were damaged, 7,411 were residential and 553 

were non–residential. All 553 of the non–residential buildings and 3,069 (about 43 percent) of the 

183 In 2011 dollars. 

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Chapter 5 

residential structures sustained either heavy/totaled or demolished damage classification, resulting in 

$1.228 billion in reported insured losses for non–residential property and $0.552 billion for residential 

property. 

Finding 10—

Among the engineered buildings surveyed by NIST, those with redundant lateral load capacity and those 

that did not depend on bracing from the roof system for lateral stability (such as certain steel and concrete 

moment frame buildings) withstood the tornado without structural collapse. Those with reinforced 

concrete roofs or composite concrete and steel roofs also withstood the tornado without structural 

collapse. Those that relied on bracing from a less robust roof system for lateral stability (such as box– 

type system (BTS) buildings with light steel roof decks) were prone to structural collapse. 

Finding 11—

The structural collapses of NIST–surveyed BTS buildings began with failure of the roof system due to 

wind uplift (failure of roof–deck–to–joist or joist–to–wall connections), which led to the loss of lateral 

bracing for perimeter walls, causing them to collapse by rotation at the base due to lateral load. Available 

design information showed that the roof connections of these buildings were adequate for code–level 

design wind pressures, making it unlikely that these buildings could have failed in wind speeds under 

115–120 mph, which are the “ultimate” (that is, sufficient for failure) speeds corresponding to the code– 

level winds. 

Finding 12—

BTS buildings, surveyed by NIST, that sustained total structural collapse had two common design 

features that increased their vulnerability to collapse in the May 22, 2011, Joplin tornado: light–gauge 

metal roof systems, and friction–only wall–to–footing connections (currently accepted practice for areas 

with low or no seismic risk). 

Finding 13—

Metal building systems (MBS) surveyed by NIST sustained significant damage to their envelopes, but no 

structural collapses of the primary rigid steel frame. 

Finding 14—

Failures of residential wood–frame buildings predominantly involved failure of the connections between 

structural components, rather than of the components themselves (roof, walls, and floor), with the 

majority involving disconnection of the roof from walls and walls from foundation. This indicates lack of 

robustness in the connections and in the continuity of the vertical load path from roof to foundation. 

Finding 15—

Better structural performance in one of the NIST–surveyed multi–family residential buildings in Joplin 

can be attributed to use of robust hurricane connectors, typically only required for residential wood–frame 

buildings in hurricane–prone regions. 

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Finding 16—

All NIST–surveyed engineered buildings that did not collapse (steel, concrete frame, and MBS), as well 

as engineered buildings that collapsed (BTS buildings), sustained significant damage to the building 

envelopes and interiors due to the combination of wind pressure, impacts by wind–borne debris, and 

subsequent water intrusion. 

Finding 17—

The failure of building envelopes at St. John’s Regional Medical Center (SJRMC), which led to loss of 

protection and subsequent extensive damage to building interiors (affecting electrical distribution and 

fixtures, water and gas pipes, HVAC systems and ductwork, and the elevator system and elevator shaft 

enclosure), was the primary cause for the complete loss of functionality of this critical facility, which 

occurred despite the robust structural system that withstood the tornado without structural collapse. 

Finding 18—

The majority of the impact–resistant windows on the fifth floor (Behavioral Health Unit) of the West 

Tower of SJRMC remained intact, whereas most regular dual–pane insulated windows at SJRMC were 

broken when exposed to the same tornado hazards. 

Finding 19—

While there was no direct evidence that roof aggregate contributed to any fatalities in Joplin, there was 

evidence that roof aggregates contributed to envelope damage in SJRMC buildings and surrounding 

structures, thus adding to the tornado debris hazard and the potential for injuries or fatalities. 

5.1.3.2 Performance of Shelters/Safe Rooms/Designated Refuge Areas 

Finding 20—

NIST found that Joplin residents had limited access to underground or tornado–resistant shelters. There 

were no community shelters or safe rooms in the City of Joplin or Jasper County at the time of the May 

22, 2011, Joplin tornado. Also, 82 percent of the homes in Joplin lacked basements. Only a few non– 

residential buildings were equipped with underground locations (e.g., basements), and none was identified 

as having a tornado–resistant shelter above ground. 

Finding 21—

While many non–residential facilities had designated refuge areas, several of these areas suffered severe 

damage and NIST found no evidence that these areas yielded positive outcomes with respect to loss of 

life. Most high–occupancy commercial and critical facilities surveyed by NIST in the tornado–affected 

area (SJRMC, schools, and big–box stores) had in–facility designated refuge areas for tornadoes. 

However, the locations of these areas were not always based solely on structural considerations. There 

are currently no design standards, requirements, or best–practice guidelines for designating refuge areas 

within existing commercial or critical buildings.184 

184 Limited guidance, focused on identifying best available refuge areas in schools, is available in FEMA P431, Tornado 

Protection: Selecting Refuge Areas in Buildings (http://www.fema.gov/media-library/assets/documents/2246?id=1563). 

NIST NCSTAR 3, Joplin Tornado Investigation 353 
 

 

 

 

 

 

 

 

 

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Finding 22—

Currently, there are optional model code provisions for the design of specially purposed shelters, but such 

shelters are not required. 

Finding 23—

Based on a few instances observed in this tornado, in–home shelters did perform well and provided life– 

safety protection to the home owners. NIST found no statistics on how many of the 7,411 damaged 

residential structures had in–home tornado shelters. 

5.1.3.3	 Performance of Lifelines 

Finding 24—

All utilities (water, gas, power) were lost in the areas most damaged by the May 22, 2011, Joplin tornado. 

The utility providers restored service to critical buildings (SJRMC, water treatment plant) within 24 

hours. 

Finding 25—

The failure of building envelopes at NIST–surveyed critical facilities, and resultant severe damage to their 

interior and internal lifeline distribution systems, was the primary cause of the facilities’ complete loss of 

functionality despite restoration of utility services within 24 hours. 

Finding 26—

In critical facilities constructed in Joplin prior to 1998, the design wind speed for high–occupancy 

buildings was higher than that specified for buildings housing the facilities’ backup power generators. 

5.1.4	 Findings Related to the Pattern, Location, and Cause of Fatalities and Injuries, 

and Associated Performance of Emergency Communications Systems and 

Public Response 

Finding 27—

During the period from 1950 (i.e., the beginning of official tornado record keeping) through 2011, 

tornadoes caused approximately 5,600 fatalities in the United States. Within an 80–mile radius around 

Joplin, 233 deaths (including those caused by the Joplin tornado) were caused by tornadoes during the 

same period. 

Finding 28—

The Missouri State Police attributed 161 deaths and the City of Joplin attributed more than 1,000 injuries 

to the Joplin tornado, which affected an area with an estimated population of 20,820. 

Finding 29—

Of the 161 deaths resulting from this tornado, 155 (96 percent) were caused by impact–related factors 

(i.e., multiple blunt force trauma to the body). The others were caused by stress–induced heart attacks, 

pneumonia, or lightning. 

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5.1.4.1 Emergency Communication Prior to May 22, 2011 

Finding 30—

There was evidence of high false–alarm rates185 among the storm–based tornado warnings officially 

issued for Joplin. From 2005 through 2011, 78 percent (14 out of 18) of the official tornado warnings 

issued for Joplin did not result in a verified tornado; this percentage was in line with the 2007–2011 

national average storm–based tornado false–alarm rate of 74.7 percent. More recently, over the 5–year 

period from 2007 through 2011, the Joplin area false–alarm rate increased to 92 percent. 

Finding 31—

Despite public perception, no evidence was found of high false–alarm rates for Joplin’s outdoor siren 

system. 186 Since 2007, the average rate of activation of the 25–siren outdoor warning system in Joplin 

was once per year (at most), not including the test activations (1 minute in duration) that occurred weekly. 

Finding 32—

Joplin residents interviewed after the Joplin tornado believed that there had been a high number of false 

alarms in Joplin from official tornado warnings and the City’s outdoor siren system prior to 2011, even 

though the siren activation rate was once per year (on average). 

5.1.4.2 Tornado History Prior to May 22, 2011 

Finding 33—

Prior to 2011, the roughly 30–square–mile City of Joplin had experienced one tornado rated EF–2 or 

greater since 1950; this tornado occurred on May 5, 1971. However, also since 1950, 182 tornadoes rated 

EF–2 or higher had struck within an 80–mile radius of the City. 

Finding 34—

Prior to the May 22, 2011, Joplin tornado, scientifically unfounded beliefs about tornado movements and 

the effects of regional topography contributed to a common public perception that the City of Joplin was 

immune to a direct tornado strike. 

5.1.4.3 Emergency Communication on May 22, 2011 

Finding 35—

Two official tornado warnings were issued on May 22, 2011. After the first official warning, Joplin’s 

sirens were sounded but no tornado occurred. After the second official warning, the siren system was 

sounded again, 4 minutes after the tornado touched down and almost exactly when the tornado entered the 

City of Joplin. Both siren soundings took the form of a continuous tone of 3 minutes duration. 

185 The NWS defines a false alarm as an unverified tornado warning. In other words, a tornado warning polygon for which no visual 

reports or damage indicators demonstrate that a tornado occurred during the valid time period of the warning. 

186 In this report, the false alarm rate for the siren system is defined as the activation of the siren system without the occurrence of a 

severe weather event in Joplin. 

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Finding 36—

The function of an alert is to grab people’s attention before/during a disaster; while the function of a 

warning is to provide information about the event and how the public should respond. Both are necessary 

in an emergency. Joplin’s outdoor siren system, which could generally be heard indoors as well as 

outside, was the primary means by which individuals were alerted to a tornado event on May 22, 2011. 

Radio, television, and word of mouth were the primary means by which individuals were provided with 

warning information on May 22, 2011. 

Finding 37—

The Joplin–Jasper County Reverse–9–1–1 telephone system was not used on May 22, 2011, due to its 

inability to disseminate information in a timely manner. It had taken up to 3 hours to get emergency calls 

out during previous uses, so it is unlikely that the system would have worked in this tornado event. 

Finding 38—

Functioning as an alerting system only, the outdoor sirens prompted many Joplin residents and visitors to 

seek further information on May 22, 2011. The multiplicity of information sources, and the conflicting 

information provided by those sources, added to the public’s confusion about the true hazard as additional 

information was sought. 

Finding 39—

Across the country, there is no standard method for sounding outdoor public siren systems, which has led 

to variations in siren usage, activation procedures, and sounding patterns among U.S. communities. Also, 

there are no nationally accepted standard protocols for the issuance of an all–clear alert following a 

warning. 

Finding 40—

Of the 155 impact–related fatalities, 135 (87 percent) involved persons who are known to have been 

located inside structures during the tornado. The structures in which these people died included both 

residential (59 percent of the 135 victims) and non–residential (41 percent) buildings. 

Finding 41—

Virtually all of the buildings in which the 135 impact–related fatalities occurred experienced maximum 

estimated winds associated with tornadoes rated EF–3 or higher. The exceptions were the Meadows 

Healthcare facility, where two of the deaths occurred, and five single–family homes that were the sites of 

six of the fatalities. 

Finding 42—

The hospital towers at SJRMC did not provide life–safety protection for all occupants, even though the 

towers did not collapse. Twelve impact–related fatalities occurred in the hospital, four of which involved 

patients in intensive care units. 

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Chapter 5 

Finding 43—

Responses to the approaching tornado among members of the public, in many cases, were delayed or 

incomplete, as was evidenced by the fatalities that occurred among individuals located outdoors, in 

vehicles, or en route within buildings to safer refuges when the tornado hit. 

Finding 44—

Two factors were found to have contributed to the delayed or incomplete public response to the Joplin 

tornado. The first was a lack of awareness of the tornado. The second was an inability to perceive 

personal risk due to one or more of the following: receipt of conflicting or uncertain information about the 

tornado; pre–existing beliefs about Joplin’s immunity to direct tornado strikes; and distrust of or 

confusion about Joplin’s emergency communications system. 

Finding 45—

The main factor that convinced individuals to take shelter was the receipt of high–intensity cues, 

including hearing or seeing the tornado approaching or witnessing others’ urgency related to taking 

protection. 

Finding 46—

No fatalities occurred in demolished, detached homes in which people took refuge in basements. 

Additionally, NIST found no evidence that any of those killed were located underground during the 

tornado. 

Finding 47—

A disproportionate number of people aged 60 years or older died or were injured as a result of this 

tornado. NIST analysis of the fatalities resulting from the Joplin tornado shows that approximately 8 

fatalities occurred per thousand people in Joplin aged 60 years and over compared with 2 fatalities per 

thousand people in Joplin under 60 years. This disproportionate result remains even after removing all 

hospital and nursing home deaths. Factors that may have contributed to this outcome include a lack of 

information flow to these individuals, a lack of supportive social networks among individuals, or inability 

of an individual to withstand or recover from tornado–induced trauma. 

RECOMMENDATIONS 

As part of its technical investigation of the Joplin tornado, NIST has developed 16 recommendations for 

improving tornado hazard characterization, for improving how buildings and shelters are designed, 

constructed, and maintained in tornado–prone regions, and for improving the emergency communications 

that warn of imminent threats from tornadoes. These recommendations are presented in three groups 

(Sections 5.2.1 through 5.2.3) that reflect the objectives and findings of the investigation. 

The first group of recommendations is focused on the characteristics of tornado hazards and their 

associated wind fields. The recommendations in the second group concern the performance of buildings, 

lifelines, and shelters and designated safe areas. The final group of recommendations relates to findings 

about the pattern, locations, and causes of tornado fatalities and injuries, the performance of emergency 

communications systems, and the public response to this tornado. 

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The recommendations call for action by specific entities with regard to the development, adoption, and 

enforcement of standards, codes, and regulations; professional and construction practices, education, and 

training; and research and development. NIST believes that these recommendations are realistic and 

appropriate, and are achievable within a reasonable period of time. 

NIST strongly urges state and local authorities having jurisdiction to adopt and enforce model building 

codes and standards. Enforcement is critical to ensuring expected levels of safety. Following good 

building practices also is critical to achieving better performance of structures during extreme events like 

tornadoes. 

5.2.1	 Recommendations Related to Tornado Hazard Characteristics and Associated 

Wind Field 

Recommendation 1—

NIST recommends that a capacity be developed and deployed that can measure and characterize actual 

tornadic wind fields, including near–surface wind fields, for use in the engineering design of buildings 

and infrastructure. This would require enhancement and widespread deployment of cost-effective, 

advanced technologies, including weather radar. 

Justification: 

NIST found that current operational weather radar technology is incapable of determining tornado 

occurrence and intensity for heights at which most structures are built. Recently proven, cost– 

effective, short–range remote sensing technologies (i.e., Collaborative Adaptive Sensing of the 

Atmosphere, or CASA radar) can be more widely implemented in tornado–prone areas as an initial 

step to serve this purpose. Although these technologies would not measure the area immediately 

adjacent to ground level, they could serve as an important bridge between higher elevations sampled 

by NWS radar and estimates of the near–surface wind field discussed later in this recommendation. 

These technologies could also be used to improve warning lead time and reduce false alarm rates for 

tornadoes (see Recommendation 16). 

NIST also found that direct, near–surface wind speed measurements relevant to the Joplin tornado 

were available from only one weather station situated well outside the tornado damage path. Reliable 

measurements of near–surface wind speed and other information (e.g., wind–induced pressure) in 

tornadoes, especially in the most intense portions of them, are lacking or nonexistent due to both the 

scarcity and durability of measuring devices. This lack of measurements makes it extremely difficult 

to understand the relationship between damage and wind speed. Improved characterization of the 

tornado hazards at elevations that are meaningful for engineering design can be achieved by 

development and use of ruggedized, tornado– and tornado debris–resistant technology capable of 

directly measuring near–surface wind speeds, wind pressure, impact loading, and turbulence 

produced by tornadoes and other extreme wind events. 

As radar–based and direct measurements of wind speed in tornadoes are lacking, indirect methods 

(e.g., tree fall) were used to assess the maximum wind speeds of the Joplin tornado. However, 

considerable uncertainty still exists in these estimations. For example, estimated maximum wind 

speeds based on tree fall analysis in the Joplin tornado were 175 mph with up to 25% of model 

uncertainty. Including uncertainty, the upper bound of maximum wind speed was estimated to be 210 

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mph. Using the EF Scale, maximum wind speeds based on damage to structures surveyed by NIST 

were estimated to be 150 mph with 10% uncertainty (± 15 mph) due to the large size of the structures 

rated. The range of wind speeds for “demolished” residential structures using the EF Scale was 110 

mph to 175 mph. Uncertainties in wind speed estimation can be reduced by improving upon existing 

techniques like tree fall and the EF Scale (Recommendation 4) as described in this report, or by 

further developing other computational or analytical methods (e.g., back–calculations from structural 

or structural–element failures, debris flight). The maximum estimated near–surface wind speeds 

derived from indirect methods suggest that the extent of damage in Joplin could have been caused by 

wind speeds lower than those associated with an EF–5 tornado (200+ mph). 

Improving measurements of the entire near–surface tornadic wind field will also be useful for 

properly assessing tornado climatology, associated probabilistic estimates of the tornado hazard, and 

for calibrating the EF Scale. Tree fall analysis of the Joplin tornado suggested that damaging wind 

speeds lasted for a longer duration over a larger spatial area than was expected based on current 

tornado hazard estimation approaches. This finding is consistent with other studies that have 

estimated wind fields in actual tornadoes. In areas subjected to the highest wind speeds in the Joplin 

tornado, the duration of wind speeds at or above wind speeds associated with the EF–2 range was 

estimated to be over 1 min and the total area of EF–3 or greater wind speeds was approximately twice 

that expected under current tornado hazard models. The wind speed duration should be thoroughly 

considered when assessing damage, estimating wind speeds, and designing structures for tornadoes. 

Interested Parties: Academia, U.S. Department of Energy (DOE), National Oceanic and 

Atmospheric Administration (NOAA)/National Weather Service (NWS), U.S. Nuclear Regulatory 

Commission (NRC), and National Science Foundation (NSF) 

Organization with Lead Responsibility for Implementation: NOAA 

Recommendation 2—

NIST recommends that information gathered and generated from tornado events (such as the Joplin 

tornado) should be stored in publicly available and easily accessible databases to aid in the improvement 

of tornado hazard characterization. 

Justification: 

Characterization of the tornado hazard in Joplin benefited from information available from radar and 

anemometer measurements, pre– and post–storm aerial imagery, ground–based damage surveys, and 

photographs, as well as from damage and property databases. Archived storage of such information in 

publicly available and easily accessible databases, especially in conjunction with a geospatial 

software platform that permits detailed mapping of tornado events, would greatly facilitate 

characterization of the tornado hazard and associated risk. 

Interested Parties: Academia, Federal Emergency Management Agency (FEMA), and National 

Geospatial–Intelligence Agency 

Organization with Lead Responsibility for Implementation: NWS 

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Recommendation 3—

NIST recommends that tornado hazard maps for use in the engineering design of buildings and 

infrastructure be developed considering spatially based estimates of the tornado hazard instead of point– 

based estimates. 

Justification: 

NIST found that current estimations of the tornado hazard using tornado area (i.e. point–based) are 

insufficient when considering populated areas. This insufficiency was demonstrated by the larger 

spatial extent and longer duration of the wind field in Joplin compared to tornado hazard models 

(Finding 4) and by the amount and effects of wind–borne debris in Joplin. Debris from structures was 

shown to have significantly contributed to the overall damage state (Findings 8, 16) and to the 

potential for injuries and fatalities in Joplin (Findings 19, 29). The extent of damage to residential 

structures in Joplin was greater than predicted based on point–based estimations of tornado damage. 

For example, it was estimated that 28 percent of the damaged residential homes had EF–3 or greater 

damage versus the 12 percent predicted for an EF–5 tornado from point–based methods, and 43 

percent of structures were estimated to have EF–2 or greater damage while only 30 percent of the tree 

fall–based wind field was estimated at EF–2 or greater. This greater–than–expected level of damage 

has also been noted in other recent, significant tornadoes that have struck populated areas, such as the 

tornadoes that damaged Oklahoma City in 1999 and Tuscaloosa in 2011. 

Also, in populated areas such as Joplin, even though only part of the community is affected 

physically, the wider community is impacted. For example, 7,411 residential structures were 

damaged in Joplin, but approximately 20,000 structures were without power following the storm, 

showing that the tornado hazard and associated risk extended beyond the tornado damage path. 

As communities continue to expand, additional risks are created by growing populations and 

population centers. Risks of populated communities were analyzed using the spatially based 

methodology across the United States. Results from the NIST analysis show that populated regions 

are at a significantly higher risk from tornado damage than what is prescribed in current point–based 

estimations. 

Tornadoes rated EF–3 or lower have accounted for approximately 96 percent of all tornadoes in the 

official record and are associated with significant fatalities and economic losses. Over one–third (36 

percent) of fatalities and about 80 percent of insured property losses have been caused by EF–3 or 

lower tornadoes. Even in tornadoes rated higher than EF–3, the majority of affected areas encounter 

EF–3 or lower wind speeds. In the case of the Joplin tornado, approximately 40 percent of the 

fatalities and up to 90 percent of the tornado area were associated with EF–3 or lower wind speeds. 

Interested Parties: American Society of Civil Engineers (ASCE), DOE, FEMA, International Code 

Council (ICC), and NRC 

Organization with Lead Responsibility for Implementation: NIST 

Recommendation 4—

NIST recommends that new damage indicators (DIs) be developed for the Enhanced Fujita tornado 

intensity scale to better distinguish between the most intense tornado events. Methodologies used in the 

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development of new DIs and associated degrees of damage (DODs) should be, to the extent possible, 

scientific in nature and quantifiable. As new information becomes available, a committee comprised of 

public and private entities should be formed with the ability to propose, accept, and implement changes to 

the EF Scale. The improved EF Scale should be adopted by NWS. 

Justification: 

NIST found that the EF Scale lacks adequate DIs and corresponding DODs for distinguishing tornado 

intensity, especially for tornadoes that cause significant damage. This lack of adequacy is due in part 

to the small sample size of intense tornadoes striking heavily populated areas. The lack of DIs and 

DODs and the overall nature of the EF Scale require subjective, non–quantitative assessment of 

tornado damage. Damage indicators (DIs) not currently in the EF Scale (e.g., tractor–trailers, 

manhole covers) were used to help determine the EF–5 designation (200+ mph) for the Joplin 

tornado. Currently there are only five DODs available for use in evaluating the DIs that can result in 

an EF–5 rating using an expected value of wind speed. 

The lack of adequate DIs and DODs and associated guidance in the EF Scale led, in part, to 

differences in wind speeds that were estimated based on damage to Joplin structures by NIST and 

other researchers, practitioners, and surveyors. In addition, the EF Scale implicitly regards wind 

speed estimates for individual structures as point estimates, and cannot accommodate cases such as 

Walmart Store #59 in Joplin, where some sections of a single, large structure were more heavily 

damaged than others. NIST’s wind speed estimation from tree fall showed that wind speeds varied 

significantly over the length of the Walmart building. A similar observation was noted by FEMA, 

after their study of both the Joplin and Tuscaloosa (and other Alabama) tornadoes. 

Further refinement of the EF Scale and its procedures will enhance the estimation of maximum wind 

speeds and subsequent EF ratings in tornadoes, by providing official surveyors with additional and 

improved guidance. Recent research has stressed that a path toward modifying the EF Scale is a 

pressing need. An iterative development process will not only enable better wind speed estimation, 

but also will lead to greater understanding of the response of structures to tornadoes. Ultimately, it 

will improve estimates of tornado hazard climatology and of the risk that tornadoes pose to the public. 

Interested Parties: Academia, Applied Technology Council (ATC), FEMA, NRC, and NSF 

Organization with Lead Responsibility for Implementation: NWS 

5.2.2	 Recommendations Related to the Performance of Buildings, 

Shelters/Designated Safe Areas, and Lifelines 

Recommendation 5—

NIST recommends that nationally accepted performance–based standards for the tornado–resistant design 

of buildings and infrastructure be developed and adopted in model codes and local regulations to enhance 

the resiliency of communities to tornado hazards. The standards should encompass tornado hazard 

characterization, performance objectives, and evaluation tools. The standards shall require that critical 

buildings and infrastructure such as hospitals and emergency operations centers be designed to remain 

operational in the event of a tornado. 

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Justification: 

Currently, there are no standards for the tornado–resistant design of ordinary buildings and 

infrastructure, except for safety–related structures in nuclear power plants and storm shelters or safe 

rooms. Even in the design standards for nuclear power plants and storm shelters(ANSI/ANS 2.3 

(2011) and ICC 500 (2008)) there are inconsistencies in the way tornado hazards are characterized, as 

reflected in the different tornado regionalization and associated tornado design wind speeds for the 

contiguous United States. 

Performance–based standards for tornado–resistant design of ordinary buildings  including critical 

facilities, commercial and residential buildings  will result in more tornado–resilient communities 

(in terms of enhanced occupants’ life safety and reduced property damage and economic loss) by 

explicitly considering tornado hazards, which will be characterized by the most up–to–date tornado 

data and risk–consistent science–based methodologies, as a structural design condition. 

The recommended standards would: 

	 Prescribe “tornado–prone areas” for design (i.e., regionalization of expected tornado wind 

speeds and wind–borne debris loading) based on a review of the most up–to–date tornado 

data and hazard mapping methodology; 

	 Specify “design tornadoes” for buildings (wind speed and debris impact loading) in 

accordance with the prescribed tornado–prone areas and based on buildings’ Risk Categories; 

and 

	 Specify “tornado performance objectives” for buildings, also based on buildings’ Risk 

Categories. An example of a tornado performance objectives matrix that prescribes the 

required performance for buildings of different risk categories is shown below: 

Risk Cat. * IV Facilities 

Risk Cat. * III 

Risk Cat. * II 

(1) Hardened area, shelter–in–place. 

(2) Public shelter. 

* Based on ASCE 7–10. 

Interested Parties: Academia, ATC, Design and construction industry (including American Concrete 

Institute [ACI], American Institute of Steel Construction [AISC], American Welding Society [AWS], 

National Association of Home Builders [NAHB], Portland Cement Association [PCA], Steel Deck 

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Institute [SDI], Steel Joist Institute [SJI], The Masonry Society [TMS]), FEMA, ICC, and NFPA 

Organization with Lead Responsibility for Implementation: ASCE 

Recommendation 6—

NIST recommends the development of risk–balanced, performance–based tornado design methodologies 

such that all building components and systems meet or exceed the same performance objectives when 

subjected to tornado hazards. 

Justification: 

There is currently no methodology for building design that specifically considers the design hazards 

associated with tornadoes. The minimum code requirements for wind loading in current building 

codes do not take into account the inconsistent performance of different building components (walls 

versus roof, structural system versus envelope, structural system versus in–facility lifeline distribution 

systems (power, gas, water)) when subjected to tornado hazards. It is frequently observed (including 

in the more recent May 20, 2013, Newcastle-Moore tornado in Oklahoma187) that the overall 

outcomes of buildings in tornadoes, in terms of building’s structural performance and functionality, 

can be critically dependent upon the performance of different building components and systems that 

may not have been designed for the same risk level (buildings’ structural systems versus their 

envelopes, for example). Failure of building envelopes, despite the robust structural system that 

could withstand the tornado without structural collapse, often resulted in extensive damage to 

building interiors (affecting electrical distribution and fixtures, water and gas pipes, HVAC systems 

and ductwork, and the elevator system and elevator shaft enclosure) and ultimately the complete loss 

of building’s functionality). 

The new performance–based tornado design methodology would: 

	 Outline risk–consistent design procedures based on a holistic approach for building design 

that encompasses the structural system, envelope, and building mechanical, electrical and 

plumbing lifeline systems. 

	 Incorporate current best tornado–resistant practices and address design approaches that, while 

satisfying current minimum code requirements, might not be tornado–resilient based on 

observed performance for different types of construction, including: 

	 For box–type system (BTS) buildings: There is a need to improve robustness and 

redundancy in lateral load resistance systems by (a) ensuring risk–consistent performance 

between the roof system and bearing walls, and (b) requiring walls to have rotational 

restraint capability (instead of friction–only) to reduce dependency on the roof as the sole 

lateral bracing for collapse prevention. 

	 For engineered steel– and concrete–frame buildings and pre–engineered metal buildings: 

These structures require consistent performance between the building envelope and the 

main wind–force resisting system (synergy between improved envelope performance 

using impact–resistant windows and the need to provide protection for special portions of 

187 Preliminary Reconnaissance of the May 20, 2013, Newcastle-Moore Tornado in Oklahoma. NIST Special Publication 1164. 

Gaithersburg, MD, December. Available at http://www.nist.gov/customcf/get_pdf.cfm?pub_id=914721. 

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critical facilities, e.g., behavioral health unit in a hospital, should be exploited in planning 

for protection of the envelope and selection of the best available refuge areas in critical 

facilities). 

	 For wood–frame and combined unreinforced masonry–wood roof truss residential 

buildings: Improved tornado performance in residential construction by requiring a 

system integrity design approach to ensure a continuous vertical load path from roof to 

foundation (robust connections between roof, walls, and foundation to ensure they remain 

connected, albeit damaged). This would improve individual building structural 

performance and at the same time reduce overall wind–borne debris hazards in tornado– 

affected communities. 

Interested Parties: Academia, ASCE, ATC, Design and construction industry (including ACI, AISC, 

AWS, NAHB, PCA, SDI, SJI, TMS), ICC, and NFPA 

Organizations with Lead Responsibility for Implementation: NIST, FEMA 

Recommendation 7—

NIST recommends that: (a) a tornado shelter standard specific for existing buildings be developed and 

referenced in model building codes; and (b) tornado shelters be installed in new and existing multi–family 

residential buildings, mercantile buildings, schools and buildings with assembly occupancies located in 

tornado hazard areas identified in the performance–based standards required by Recommendation 5. 

Justification: 

 NIST found inadequate performance among the best available refuge areas in the high– 

occupancy commercial BTS buildings that it surveyed. 

	 Without community–based shelters or shelters/safe rooms in multi–family housing and 

nursing homes, residents of these buildings really had no effective sheltering options during 

the Joplin tornado. 

	 Home Depot found that it was feasible to include a hardened refuge area in the store that it 

built to replace the store demolished in the May 22, 2011, Joplin tornado (the earlier store had 

no such area). 

	 There are changes in the forthcoming 2015 IBC that will require installation of tornado 

shelters at newly constructed schools, 911 call stations, emergency operation centers, and 

fire, rescue, ambulance and police stations located in the 250 mph wind speed zone shown on 

the tornado hazard map in Fig. 3-5. Recommendation 7 expands on these changes by calling 

for additional types of new structures to be covered by shelter requirements, and extending 

such requirements to certain types of existing structures. 

Interested Parties: Academia, FEMA, NAHB, NFPA, and States and authorities having jurisdiction 

(AHJ) in tornado–prone areas 

Organization with Lead Responsibility for Implementation: ICC 

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Recommendation 8—

NIST recommends the development and implementation of uniform national guidelines that enable 

communities to create safe and effective public sheltering strategies. The guidelines should address 

planning for siting, designing, installing, and operating public tornado shelters within the community. 

Justification: 

NIST found that an overwhelming majority of the fatalities in Joplin (96 percent) were caused by 

impact–related factors (usually labeled by authorities as multiple blunt–force trauma to the body). A 

majority of these victims (83.8 percent) were located inside buildings when they were fatally injured. 

And, many of the buildings they occupied were demolished by the storm, meaning that the roof and 

walls collapsed, or sustained a “heavy/totaled” level of damage, where there was loss of a significant 

portion of or the entire roof system, which exposed the building interior to weather damage and 

debris. 

Additionally, NIST found that individuals had often sheltered above ground in these heavily damaged 

buildings, or in vehicles, and that few among the affected populace had access to underground or 

tornado–resistant shelters. There were no community shelters or safe rooms (defined as structures 

designed in accordance with either the ICC 500 standard or FEMA 361 guidance) in the City of 

Joplin or Jasper County at the time of the May 22, 2011, Joplin tornado. Also, 82 percent of the 

homes in affected area in Joplin lacked basements. Only a few commercial buildings were equipped 

with underground locations, and none with tornado–resistant above–ground shelters. Although 

above–ground residential crawl spaces were often available for sheltering, residents generally did not 

use them during the May 22, 2011, Joplin tornado because they perceived that they had insufficient 

time to access them or that the crawl spaces would be too difficult or uncomfortable to use as shelters. 

In this particular storm, the residents of Joplin might have benefited from more sheltering options and 

potentially sustained fewer deaths and injuries. However, NIST recommends the development of 

guidelines that municipalities in tornado–prone areas can use to design and implement their own 

sheltering solutions, rather than mandating a single sheltering strategy (or solution) for every 

community located in these areas. The guidelines would allow each community to assess their 

current sheltering capabilities and to develop the safest, most efficient, and most economical 

sheltering strategy possible based upon the needs of the community (e.g., population size, public 

comfort with alternative sheltering solutions, training and education, public vulnerabilities), the types 

of construction within the community, and cost. 

Interested Parties: International Association of Emergency Managers (IAEM), International 

Association of Fire Chiefs (IAFC), ICC, National Association of Counties (NAC), National 

Conference of State Legislators (NCSL), National Emergency Management Association (NEMA), 

NFPA, NSF, and NWS 

Organization with Lead Responsibility for Implementation: FEMA 

Recommendation 9—

NIST recommends that uniform guidelines be developed and implemented nationwide for conducting 

assessment of tornado risk to buildings and designating best available tornado refuge areas as an interim 

NIST NCSTAR 3, Joplin Tornado Investigation 365 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 5 

measure within buildings until permanent measures fully consistent with Recommendations 5 and 7 are 

implemented. 

Justification: 

NIST found that, based on its surveys of affected buildings and its interviews with building occupants 

in Joplin, practices for selecting best available refuge areas were ad hoc and had varying degrees of 

effectiveness, and could have been based on considerations other than structural safety (e.g., 

proximity to an emergency exit or bathroom). In addition, NIST found that the guidance currently 

available on selecting refuge areas within buildings is either too general, on the one hand, or too 

specific to a given type of structural system, on the other. 

NIST found some tornado–resistant design features in the BTS buildings that it surveyed in Joplin, 

including a partially fixed–end condition for perimeter walls (designed to brace against accidental 

truck impacts but not required in regions of low seismic hazard) that appeared to have kept walls from 

collapsing in the tornado. Such features should be exploited in selecting best available refuge areas in 

BTS buildings in tornado–prone areas. The recommended guidelines would help responsible parties 

identify such features and select the most effective refuge areas in different types of buildings in 

tornado–prone areas. 

Interested Parties: Academia, DHS S&T, IAEM, IAFC, ICC, NAC, NCSL, NEMA, NFPA, and 

States and AHJs in tornado–prone areas 

Organization with Lead Responsibility for Implementation: FEMA 

Recommendation 10—

NIST recommends that aggregate used as surfacing for roof coverings and aggregate, gravel, or stone 

used as ballast be prohibited on buildings of any height located in a tornado–prone region. 

Justification: 

Section 1504.8 of the 2012 International Building Code (IBC) prohibits the use of aggregate as roof 

surfacing materials and as roof ballast for buildings in hurricane–prone regions and buildings in non– 

hurricane regions with mean roof heights (MRH) that exceed a specified height limit (limit varies 

depending on the required basic wind speed and exposure category of the building). For Joplin (90 

mph basic wind speed and Exposure Category B), aggregate roof ballast was prohibited only for 

buildings with a MRH exceeding 110 ft. Several buildings at SJRMC with roof heights less than 

110 ft had aggregate roof ballast and the roof aggregates were found to have contributed to the wind– 

borne debris hazard during the Joplin tornado. 

Interested Parties: ASCE, NFPA, Single Ply Roofing Industry (SPRI), and States and AHJs 

Organization with Lead Responsibility for Implementation: ICC 

Recommendation 11—

NIST recommends that enclosures of egress systems (elevators, exits, stairways) in critical facilities in 

tornado–prone areas be designed to maintain their functional integrity when subjected to tornado hazards. 

366 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 5 

Justification: 

Section 713.3 of the 2012 IBC stipulates that enclosures for elevator shafts shall be of materials 

permitted by the building type of construction. This could mean non–impact–resistant materials such 

as gypsum board on steel studs are allowed for use as elevator shaft enclosure, as was the case for the 

elevator shaft in SJRMC’s elevator tower. It was found that the shaft enclosure at SJRMC was 

damaged due to debris infiltration and thus could have impeded the functionality of the elevator even 

if the power had not been lost. 

Interested Parties: Building Owners and Managers Association International (BOMA) 

Organization with Lead Responsibility for Implementation: ICC, NFPA 

Recommendation 12—

NIST recommends that (a) tornado vulnerability assessment guidelines for critical facilities be developed 

and (b) owners and operators of existing critical facilities in tornado–prone areas perform tornado 

vulnerability assessments, which includes steps to protect the functionality of (1) backup power supplies, 

(2) vertical movement within the building (elevator equipment and shaft enclosures), and (3) means of 

egress illumination (battery–powered lighting in addition to backup power), in a tornado event. 

Justification: 

Loss of backup power supplies, vertical movement, and means of egress illumination occurred 

frequently in existing critical facilities during tornadoes. This can result in hazardous conditions for 

post–tornado rescue and evacuation, and ultimately loss of building functionality. Pre–tornado 

assessment and identification of vulnerabilities of critical facilities to ensure continuity and integrity 

of backup power supplies, vertical movement, and means of egress illumination, based on lessons 

learned from past tornadoes, should result in improved outcomes with regard to rescue operations, 

safe evacuation and continued operation of existing critical facilities. 

Interested Parties: BOMA, DHS IP, DHS S&T, International Facility Managers Association, 

NFPA, and States and AHJs 

Organization with Lead Responsibility for Implementation: FEMA 

5.2.3	 Recommendations Related to the Pattern, Location, and Cause of Fatalities 

and Injuries, and Associated Performance of Emergency Communications 

Systems and Public Response 

Recommendation 13—

NIST recommends the development of national codes and standards and uniform guidance for clear, 

consistent, recognizable, and accurate emergency communications, encompassing alerts and warnings, to 

enable safe, effective, and timely responses among individuals, organizations, and communities in the 

path of storms having the potential to create tornadoes. 

NIST also recommends that emergency managers, the NWS, and the media develop a joint plan and take 

steps to make sure that accurate and consistent emergency alert and warning information is communicated 

NIST NCSTAR 3, Joplin Tornado Investigation 367 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 5 

in a timely manner to enhance the situational awareness of community residents, visitors, and emergency 

responders affected by an event. 

Justification: 

NIST found that many U.S. communities, even within the same state or region of a state, create and 

disseminate emergency communications for tornadoes in different ways. In Missouri, for example, 

according to the emergency manager (EM) for Joplin–Jasper County, it is the responsibility of the 

EM of each municipality in Jasper County to design the emergency communication system used to 

alert and warn the local populace about tornadoes. Currently, no federal, state, or local guidance or 

requirements exist that standardize such systems, which has resulted in different systems and 

operating practices (at least for the use of outdoor warning sirens for tornadoes) from one 

municipality to another. NIST also found that some Joplin tornado survivors expressed confusion 

regarding the protocol used for tornado sirens in the city. The main aspect of confusion was why the 

first and second siren soundings stopped after 3 minutes had elapsed, because some associated these 

cessations as signaling the end of the emergency. However, the 3 minute siren duration was part of 

Joplin’s outdoor warning siren protocol, which was available online as well as in the City’s 

emergency plans. 

Therefore, NIST recommends the development of national codes, standards, and/or guidance for the 

creation and dissemination of clear, consistent, and accurate emergency communications for 

tornadoes. Especially important is the inclusion of guidance on both alerts and warning information. 

Alerts, such as the activation of outdoor sirens, are meant to grab people’s attention, whereas 

warnings provide information on the nature of the emergency and what actions people should take. 

The provision of warning information along with the siren alerts could have enhanced the public’s 

understanding of why the sirens were sounding in Joplin. Understanding could also have been 

enhanced had the public received timely and consistent rather than conflicting information about 

weather developments before the tornado struck. NIST recommends that the joint efforts described 

above involve emergency management, the NWS, and the media, to avoid conflicting messaging in 

emergencies. 

Interested Parties: Academia, FEMA, IAEM, ICC, NEMA, and NWS 

Organization with Lead Responsibility for Implementation: NFPA 

Recommendation 14—

NIST recommends that the full range of current and next–generation emergency communication “push” 

technologies (e.g., GPS–based mobile alerts and warnings, reverse 9–1–1, outdoor siren systems with 

voice communication, NOAA weather radios) be deployed and utilized to maximize each individual’s 

opportunity to receive emergency information and respond safely, effectively, and in a timely fashion. 

Justification: 

NIST found that people’s responses to the impending storm, in many cases, were delayed or 

incomplete, which resulted in some fatalities occurring outside, in vehicles, and among individuals 

rushing to obtain safer refuge when the tornado struck. Among those who did not respond or delayed 

their response, NIST found that a lack of awareness of the tornado contributed to such behavior. 

There were individuals within the tornado’s damage path who were unaware of the impending 

368 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 5 

tornado because they did not receive any tornado–related alerts or warnings on May 22, 2011, 

including individuals with hearing loss, individuals who were asleep before the storm hit, and persons 

who were disconnected from available modes of emergency communication. Additionally, the use of 

NOAA weather radios or subscription–based mobile alerting systems was not prevalent among Joplin 

residents and visitors. 

Therefore, NIST recommends that the full range of current and next–generation emergency 

communication “push” technologies should be evaluated for future use in disseminating alert and 

warning information. “Push” technologies are those that do not rely on the user to actively search for 

information. One example of an alerting push technology is outdoor siren systems. However, in 

Joplin the siren system was designed to alert only individuals who were located outdoors, even 

though many individuals could hear these alerts inside their homes and businesses throughout the 

city. Additionally, no associated warning information was disseminated with these alerts on May 22, 

2011, causing individuals to have to search for additional information about the event. 

There are new technologies being explored that deliver both alert and warning information based 

upon geographic location. One of the newest sources of such technology is the Commercial Mobile 

Alert System (CMAS). CMAS is a partnership between FEMA, the Federal Communications 

Commission (FCC), and wireless carriers, that allows public–safety authorities (either local EMs or 

the NWS) to send 90–character, geographically targeted, text–like alerts to the public through their 

mobile devices. Unlike most mobile services, this is not an opt–in system. Rather, individuals with 

enabled mobile devices who are within a certain distance of activated cell towers will receive the alert 

messages. These alerts will bypass the regular networks that often bog down due to increased traffic 

during emergencies. 

However, there are limitations associated with this new and exciting technology. For example, 

notification resources such as cell phones and social networking sites like Twitter have restrictions on 

the length of individual alert or warning messages. Additionally, individuals who are sleeping still 

may not receive these types of mobile alerts, especially those in deeper stages of sleep. Therefore, 

NIST recommends additional exploration of technologies that are able to reach more vulnerable 

populations in tornadoes, namely those who are sleeping or have visual and/or hearing impairments. 

Interested Parties: Academia, DHS, FCC, IAFC, NEMA, NFPA, and NWS 

Organization with Lead Responsibility for Implementation: FEMA 

Recommendation 15—

NIST recommends research be conducted to identify the factors that will significantly enhance public 

perception of personal risk and promote rapid and effective public response during emergencies, 

including tornadoes. 

Justification: 

NIST found that the prevalent “take shelter now” trigger for individuals responsible for their own 

protective decision–making (e.g., those located at home) in Joplin was the receipt of high–intensity 

cues, including hearing or seeing the tornado approaching or witnessing others’ urgent efforts to seek 

protection from the storm. One media source, credited by some with saving lives before the tornado 

NIST NCSTAR 3, Joplin Tornado Investigation 369 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 5 

hit, had a broadcast which included a video of the approaching tornado and the station’s newscaster 

pleading with listeners to “Take cover now!” Both the video and the urgent tone of the broadcaster 

were highlighted as increasing individuals’ perceived risk associated with the event, prompting them 

to take action before the tornado hit. 

The NWS is currently testing a new method of including stronger–worded text in tornado warning 

messages for higher–severity storms. However, little research or guidance is available on how to 

disseminate messages both visually and audibly to increase risk perception. While human factors and 

ergonomics research is available on ways of increasing alert or message urgency (e.g., through 

specific types of tones or voice pacing or frequency), little research or guidance is available on the 

effectiveness of such technologies in disaster situations. Therefore, research should explore various 

ways to create and disseminate warnings, as well as to train and educate the public to achieve higher 

levels of perceived risk among community residents when a tornado is imminent. 

Interested Parties: Academia, DHS, ICC, NFPA, and NWS 

Organization with Lead Responsibility for Implementation: NSF, NIST 

Recommendation 16—

NIST recommends that technology be developed to provide tornado threat information to emergency 

managers, policy officials, and the media on a spatially resolved real–time basis to supplement the 

currently deployed official binary warn/no warn system. 

Justification: 

NIST found evidence of high false–alarm rates for tornado warnings in Joplin, which were more 

prevalent among NWS–issued tornado warnings than siren activations. Additionally, NIST found 

that, prior to the Joplin tornado, there was a pervasive confidence among Joplin residents that a 

tornado was unlikely to strike their city. One factor that contributed to this confidence was the 

public’s perception of a high number of false alarms in Joplin. 

NIST also found that between July 1, 2005 and May 25, 2011, the NWS issued 18 storm–based 

tornado warnings for all or some part of Joplin. Of these 18 warnings, only 4 were validated by 

subsequent tornado sightings, which yielded a false–alarm rate for the Joplin area of 78 percent (or 

14/18). This rate was similar to the 2007–2011 national average false–alarm rate for NWS storm– 

based tornado warnings, which was 74.7 percent. Over the most recent 5–year period from 2007 to 

May 22, 2011, the NWS issued 12 tornado warnings for Joplin, using storm–based warnings, of 

which only one was verified as an actual storm event. Therefore, during this more recent period, the 

false–alarm rate for NWS warnings in Joplin had increased to 92 percent. 

NIST recommends that the NWS consider improvements to its provision of threat assessments. To 

supplement the binary warn/no warn system that is currently employed for official warnings, NIST 

recommends that the NWS consider moving toward providing frequently updated gridded 

probabilistic hazard information, which could be merged with other GIS information to provide better 

hazard information and reduce false–alarm rates. 

Interested Parties: FEMA, IAEM, Media industry, NEMA, and NFPA 

Organization with Lead Responsibility for Implementation: NOAA 

370 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

Appendix A 

MESOSCALE DISCUSSIONS ISSUED ON MAY 22, 2011,
	

THAT INCLUDED JOPLIN
	

A.1 MESOSCALE DISCUSSION 853 

Source: NOAA (www.spc.noaa.gov/products/md/2011/md0853.html)

 MESOSCALE DISCUSSION 0853

 NWS STORM PREDICTION CENTER NORMAN OK

 0106 PM CDT SUN MAY 22 2011

 AREAS AFFECTED...ERN KS...NERN OK...MUCH OF SRN AND SWRN MO...NRN AR

 CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY 

VALID 221806Z – 222000Z

 A TORNADO WATCH WILL BE ISSUED SHORTLY.

 AN EXTREMELY UNSTABLE AIR MASS HAS DEVELOPED E OF THE DRYLINE WITH

 DEWPOINTS NEAR 70 F BENEATH STEEP MID LEVEL LAPSE RATES. NEARLY ALL

 CONVECTIVE INHIBITION HAS BEEN ERODED...THUS EXPECTED CU ALONG THE

 DRYLINE TO ERUPT INTO INTENSE SUPERCELLS. EXTREMELY LARGE HAIL IS 

NIST NCSTAR 3, Joplin Tornado Investigation 371 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

Appendix A 

LIKELY...AND ALTHOUGH LOW LEVEL SHEAR IS A BIT MARGINAL...IT WILL BE

 MORE THAN SUFFICIENT FOR TORNADOES GIVEN EXTREME INSTABILITY.

 ..JEWELL.. 05/22/2011

 ATTN...WFO...LSX...LZK...SGF...EAX...TSA...ICT...

 LAT...LON 36619153 36159187 36009275 36049408 36049519 36099643

 36459673 36859655 37749573 38249409 38389294 38389201 

37969159 37169139 36619153 

A.2 MESOSCALE DISCUSSION 862 

Source: NOAA (www.spc.noaa.gov/products/md/2011/md0862.html)

 MESOSCALE DISCUSSION 0862

 NWS STORM PREDICTION CENTER NORMAN OK

 0348 PM CDT SUN MAY 22 2011

 AREAS AFFECTED...ERN OK...SERN KS...SWRN MO

 CONCERNING...TORNADO WATCH 325...

 VALID 222048Z – 222245Z

 THE SEVERE WEATHER THREAT FOR TORNADO WATCH 325 CONTINUES.

 VIGOROUS CONVECTION CONTINUE TO INTENSIFY ALONG THE DRYLINE FROM WRN 

372 NIST NCSTAR 3, Joplin Tornado Investigation
 

 

 

 

 

 

 

 

 

Appendix A 

MO INTO SERN KS. A MODIFIED 19Z SGF SOUNDING USING OBSERVED SURFACE

 OBSERVATIONS ALONG THE DRYLINE YIELDS OVER 5000 J/KG MUCAPE WITH A

 300 MB LI OF –19C. ALSO DEPICTED IN THIS SOUNDING...AND ON NDS AND

 CNW PROFILERS...IS 40–50 KT MID LEVEL FLOW ATOP VEERING LOW LEVEL

 FLOW...MORE THAN SUFFICIENT FOR SUPERCELLS. EXISTING STORMS WILL

 PERSIST WITH AN EXTREME HAIL THREAT AS WELL AS THE POSSIBILITY OF

 CYCLIC TORNADOES.

 TO THE S...A SUBSTANTIAL CU FIELD REMAINS OVER NERN OK...AND SWD

 ACROSS ERN OK WHERE DEWPOINTS ARE IN EXCESS OF 72 F. HERE...SBCAPE

 IS AVERAGING 5500–6000 J/KG. HKL AND PRC PROFILERS ALSO INDICATE

 INCREASING MID TO UPPER LEVEL FLOW TO 50–60 KTS ABOVE 9 KM. STRONG

 HEATING PERSISTS NEAR THE DRYLINE...ALTHOUGH CONVERGENCE IS WEAK.

 TOWERING CU PERSIST ALONG THE DRYLINE. ANY ROBUST STORMS THAT DO

 FORM WILL CERTAINLY PRODUCE VERY LARGE HAIL AND HAVE A THREAT OF

 TORNADOES.

 ..JEWELL.. 05/22/2011

 ATTN...WFO...LSX...LZK...SGF...EAX...TSA...ICT...OUN... 

LAT...LON 35239402 35239668 38769406 38759127 35239402 

A.3 MESOSCALE DISCUSSION 867 

Source: NOAA (www.spc.noaa.gov/products/md/2011/md0867.html) 

NIST NCSTAR 3, Joplin Tornado Investigation 373
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Appendix A 

MESOSCALE DISCUSSION 0867

 NWS STORM PREDICTION CENTER NORMAN OK

 0610 PM CDT SUN MAY 22 2011

 AREAS AFFECTED...CNTRL/SWRN MO...SERN KS...NWRN AR...NERN OK

 CONCERNING...TORNADO WATCH 325...

 VALID 222310Z – 230015Z

 THE SEVERE WEATHER THREAT FOR TORNADO WATCH 325 CONTINUES.

 AT 2245–23Z...REGIONAL AND HI–RES RADAR IMAGERY SHOW A CLUSTER OF HP

 SUPERCELLS MOVING E–SE AT AROUND 30 KT. MOST SIGNIFICANT STORM /WITH

 A HISTORY OF PRODUCING A TORNADO/ IN THIS CLUSTER WAS LOCATED NEAR

 JOPLIN AT 2248Z. SGF VWP SHOWS ENLARGED LOW–LEVEL HODOGRAPH

 STRUCTURE...WITH 0–1 KM SRH NEAR 200 M2 S–2. GIVEN STRONG SHEAR

 PROFILES RESIDE DOWNSTREAM OVER SWRN MO...ALONG WITH AXIS OF MLCAPE

 VALUES FROM 2500–4000 J/KG...TORNADO THREAT /POTENTIALLY STRONG/

 ALONG WITH VERY LARGE HAIL SHOULD PERSIST AS HP SUPERCELL CLUSTER

 MOVES ACROSS THE REMAINDER OF SWRN MO. FARTHER N OVER CNTRL

 MO...CLUSTER OF STORMS WAS MOVING E ACROSS AN ENVIRONMENT

 CHARACTERIZED BY STRONG INSTABILITY AND FAVORABLE SHEAR PROFILES FOR

 SUPERCELLS POSING A THREAT FOR TORNADOES...LARGE HAIL AND DAMAGING

 WINDS. 

MEANWHILE OVER NERN OK...SUSTAINED STORM DEVELOPMENT APPEARS TO BE

 TAKING PLACE BASED ON RECENT REGIONAL REFLECTIVITY. WITH SURFACE

 CONDITIONS CHARACTERIZED BY TEMPERATURES IN THE MID 80S AND

 DEWPOINTS IN THE LOW 70S...AND 700–500 MB LAPSE RATES AROUND 7

 C/KM...EXTREME INSTABILITY RESIDES AHEAD OF THIS NEW DEVELOPMENT

 /MLCAPE VALUES NEAR 4000 J PER KG/. AREA VWP/S AND RUC SOUNDINGS

 SHOW FAVORABLE WIND PROFILES FOR SUPERCELL DEVELOPMENT AS THIS

 ACTIVITY MOVES DOWNSTREAM ACROSS NERN OK INTO NWRN AR...WITH THE

 POTENTIAL FOR VERY LARGE HAIL AND TORNADOES CONTINUING INTO THE

 EVENING HRS.

 OVER S–CNTRL OK...LEFT MOVING SUPERCELL IS RAPIDLY MOVING N TOWARD

 THE SWRN CORNER OF WW 325. THIS STORM WILL POSE A THREAT FOR LARGE

 HAIL IF IT PERSISTS INTO E–CNTRL/NERN OK.

 ..GARNER.. 05/22/2011

 ATTN...WFO...LSX...LZK...SGF...EAX...TSA...ICT...OUN... 

LAT...LON 38779404 38769126 35229404 35229670 38779404 

374 NIST NCSTAR 3, Joplin Tornado Investigation
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Appendix B 

EF–SCALE RATING FOR RANDOM RESIDENTIAL STRUCTURES 

Building 

ID Number188 

Pictometry 

Analysis 

Damage 

Level1 

NIST EF Analysis NIST Wind Field Model 

Damage 

Indicator189 

(DI) 

Degree of 

Damage190 

(DOD) 

Estimated 

Wind Speed 

(mph) 

Estimated 

Wind Speed 

(mph) 

Closest Grid 

Point 

Number 

1387 Light 2 1 65 75 2691 

1528 Light 2 2 75 100 3712 

1957 Light 2 2 79 100 500 

3442 Light 2 2/4 85 115 1542 

3453 Light 2 1/2 85 90 1504 

3914 Light 2 1/2 75 100 1664 

4167 Light 2 2/4 85 130 1855 

5841 Light 2 1 65 90 1326 

6350 Light 2 2/4 85 110 1732 

8317 Light 2 2 85 110 1744 

565 Medium 2 4 90 90 1908 

1313 Medium 2 2 80 100 1489 

2357 Medium 2 2/4 85 155 858 

2674 Medium 2 2/4 85 135 1099 

3009 Medium 2 4 100 105 1221 

188 ® Data Source: Pictometry . Used with Permission. 

189 DI 2 description: One–and Two–Family Residences (TTU, 2006). 

190 Degree of Damage descriptions for DI 2 (TTU, 2006): 

DOD Description 

1 Threshold of visible damage 

2 Loss of roof covering material (<20%), gutters and/or awning; loss of vinyl or metal siding 

3 Broken glass in doors and windows 

4 Uplift of roof deck and loss of significant roof covering material (>20%); collapse of chimney; garage doors collapse inward; 

failure of porch or carport 

5 Entire house shifts off foundation 

6 Large sections of roof structure removed; most walls remain standing 

7 Exterior walls collapsed 

8 Most walls collapsed, except small interior rooms 

9 All walls 

10 Destruction of engineered and/or well–constructed residence; slab swept clean 

NIST NCSTAR 3, Joplin Tornado Investigation 375 
 

Appendix B 

Building 

ID Number188 

Pictometry 

Analysis 

Damage 

Level1 

NIST EF Analysis NIST Wind Field Model 

Damage 

Indicator189 

(DI) 

Degree of 

Damage190 

(DOD) 

Estimated 

Wind Speed 

(mph) 

Estimated 

Wind Speed 

(mph) 

Closest Grid 

Point 

Number 

4254 Medium 2 4 95 140 1896 

5540 Medium 2 4/6 110 110 528 

6002 Medium 2 6 120 135 1412 

6188 Medium 2 4 95 130 1613 

7101 Medium 2 2/4 90 80 4943 

1761 Heavy to 

Totaled 

2 6 115 140 4147 

2831 Heavy to 

Totaled 

2 4/6 95 135 1139 

2874 Heavy to 

Totaled 

2 4 115 170 1136 

3948 Heavy to 

Totaled 

2 4 115 105 1704 

4954 Heavy to 

Totaled 

2 4/6 105 160 2823 

5075 Heavy to 

Totaled 

2 6 130 165 173 

5121 Heavy to 

Totaled 

2 6 125 170 92 

5364 Heavy to 

Totaled 

2 6 125 105 207 

5570 Heavy to 

Totaled 

2 6 122 125 650 

5797 Heavy to 

Totaled 

2 6/7 125 170 1293 

1403 Demolished 2 6 130 170 3106 

1580 Demolished 2 6 120 160 3788 

3559 Demolished 2 6/7 130 170 1495 

3683 Demolished 2 8/9 155 165 1619 

3781 Demolished 2 6 130 170 1656 

4321 Demolished 2 8/9 160 170 2020 

4672 Demolished 2 9 175 170 2584 

5502 Demolished 2 9 175 170 374 

5888 Demolished 2 4 110 170 1415 

7181 Demolished 2 8 155 170 4776 

376 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

Appendix C 

MODEL GRID COORDINATES 

Figure 2–16 illustrates grid points spaced 0.05 miles (264 ft, 80 m) apart throughout Joplin. Each grid 

point (X, Y) was given corresponding latitude and longitude values based on the beginning of the tornado 

track (tornado center). This location was different than the initial tornado touchdown location. In 

projected coordinates (North American Datum (NAD) 1983 – Missouri West Federal Information 

Processing Standard (FIPS) 2403 – Feet) used in the ArcGIS layer, the initial tornado center corresponds 

to (Xc, Yc) = (2770845 ft, 323676 ft). In latitude and longitude these coordinates are (Xc, Yc) = (37.0557, 

–94.5612), i.e., 37.0557 degrees North, 94.5612 degrees West. The values of Xc and Yc were set as X = 0 

miles and Y = 0 miles in the computer program responsible for translating the tornado through the grid. 

Although the tornado was initialized at X = 0 (X = 2770845), the X value corresponding to the first set of 

grid points was set at X = 0.65 miles (or X = 2770845 + (0.65)(5280) = 2774277 ft). This X value 

corresponds approximately to Schifferdecker Avenue. The choice of this particular value of X to start the 

grid points was based on using aerial photos to estimate when the tornado became one entity (i.e., 

multiple vortices not apparent) based on tree fall patterns. For ease of explanation, the X and Y values 

used in this section will be referenced from X = 0 miles and Y = 0 miles. 

NIST NCSTAR 3, Joplin Tornado Investigation 377 
 

Appendix C 

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NIST NCSTAR 3, Joplin Tornado Investigation 378 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Appendix D 

TORNADO WIND FIELD MODEL 

The main effects plots (see example in Figure D–1) show how the average output parameter varies given 

certain input parameters. So, for example, if three values of α are tested (25, 50, and 75 degrees for 

example), the main effects plot would show the average values of some output parameter (e.g., DR) given 

those three values. From the main effects plot, therefore, it is possible to determine how much of an 

effect varying an input parameter has on an output parameter. 

The interaction effects plots (example in Figure D–1) illustrate the effects that various combinations of 

(interactions among) input parameters have on output parameters. For example, the three α values 

mentioned above could be compared to the DR values that result when a specific RMW value is used. 

From Figure D–1, it is possible to infer which specific input parameters have significant influence over 

the output parameters. For tree fall direction (β), all input parameters have effects on its value. These 

effects are denoted by the slopes of the main effects plot (Figure D–1, top). For example, increasing the 

Gmax parameter induces, on average, a clockwise rotation of the angle β, while decreasing α also causes a 

clockwise rotation of β. By using the interaction effects plot (Figure D–1, bottom), specific values of an 

input parameter can be eliminated quickly, provided there is high confidence regarding the value of an 

output parameter. For example, if DR is observed to be around 2.0, the value of α is likely around 20 

degrees. The DR value given α = 20 degrees remains consistent even when varying the other input 

parameters (e.g., changing RMW from 0.10 miles to 0.20 miles does not significantly affect DR). 

Therefore, DR is a strong predictor of α. 

The initial ranges of all Rankine vortex input parameters, mentioned earlier, were narrowed to smaller 

ranges based on graphically comparing the observed output parameters at selected locations (Table 2–4) 

with the model outputs at these locations using the interaction effects plot (e.g., Figure D–1). Input 

values that clearly did not correspond with the observed and model output values were eliminated. 

Uncertainty in the observations in Table 2–4 was also taken into consideration when selecting the 

narrower ranges. These narrower ranges (shown in Table D–1) were then used as “best matches” of input

parameters to the observations and as final inputs for the wind field model through a second full factorial 

design. 

Table D–1 shows the final input parameter ranges used for the analysis. Mile points (X values) shown 

reflect either a change in θT or change in RMW. As estimated by tree fall, except in the early stages of the 

tornado, the Rankine vortex parameter ranges remained the same. This suggests that the tornado 

maintained its size and intensity throughout the city of Joplin. Initial values of RMW were kept fixed 

(before grid development) to generate a match to observed DW and DR values from mile points X = 0.69 

to 1.22, shown in Table 2–4. The best estimated values for the Rankine vortex model were assumed to be 

in the center of the input parameter ranges (e.g., α = 20 degrees).

NIST NCSTAR 3, Joplin Tornado Investigation 379 
 

 

Appendix D 

Figure D–1. Main (top) and interaction (bottom) effects plots for input and output 

parameters. 

380 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

Appendix D 

Table D–1. Final input parameter ranges. 

Mile Point 

(X) 

Radius of 

Maximum Wind 

(RMW) (miles) Phi Gmax 

Alpha 

(degrees) 

0.00 0.07 0.6–0.7 4.5–5.0 15–25 

0.33 0.10 0.6–0.7 4.5–5.0 15–25 

0.52 0.11 0.6–0.7 4.5–5.0 15–25 

0.65 0.12 0.6–0.7 4.5–5.0 15–25 

1.22 0.12–0.14 0.6–0.7 4.5–5.0 15–25 

2.10 0.14–0.18 0.6–0.7 4.5–5.0 15–25 

2.68 0.14–0.18 0.6–0.7 4.5–5.0 15–25 

3.14 0.14–0.18 0.6–0.7 4.5–5.0 15–25 

3.69 0.14–0.18 0.6–0.7 4.5–5.0 15–25 

5.18 0.14–0.18 0.6–0.7 4.5–5.0 15–25 

6.01 0.14–0.18 0.6–0.7 4.5–5.0 15–25 

6.47 0.14–0.18 0.6–0.7 4.5–5.0 15–25 

6.77 0.14–0.18 0.6–0.7 4.5–5.0 15–25 

This process will now be explained for a specific area in Joplin. This area is defined as X = 2.1 miles (X 

= 2.1 miles in projected coordinates) and all Y values associated with that specific X value. This area is 

“boxed” in Figure D–2. Near X = 2.1 miles and all associated Y locations, DW was observed to be 

approximately 0.9 miles and DR was estimated to be around 2.0, as shown in Table 2–4. For this 

example the ranges in Table D–1 were used in the factorial design. For example, only Gmax = 4.5 and 

Gmax = 5.0 were used. This example then has 64 different combinations (2 Gmax, 2 RMW, 2 φ, 2 α, 2 Vcrit, 

and 2 VT; 26 = 64) of parameters at X = 2.1 miles. This means that there are 64 different wind speed and 

direction time histories at each grid point and 64 total pairs of DW and DR values for the set of points 

corresponding to X = 2.1 miles. As an example, histograms of the 64 values of DW and DR are shown in 

Figure D–3. Values shown in Figure D–3 are within the bounds of the observed (i.e., estimated) DW (0.9 

miles) and DR (2.0) at this location, suggesting that an acceptable range of parameters was used in the 

factorial design. 

The observed DW and DR for this location (X = 2.1 miles) are compared to the interaction plots shown in 

Figure D–4. Starting from the top left and the Gmax parameter, it is evident that regardless of 

interactions with other input parameters in the Rankine vortex, higher Gmax values lead to higher values 

of DW. Higher DW values would be expected since a higher Gmax leads to higher values of wind speed. 

Considering interactions, higher values of RMW (R in ) coupled with higher values of Gmax leads to 

high DW values. This interaction is opposite when considering Vcrit (Vc in Figure D–4), as a lower Vcrit 

leads to higher values of DW. 

NIST NCSTAR 3, Joplin Tornado Investigation 381 
 

 

 

 

Appendix D 

This is also expected, as a higher critical tree fall wind speed would cause less tree damage. Changing the 

α parameter does not affect the values of DW, while increasing φ values, which essentially reduces the 

extent of stronger wind speeds, reduce DW on average. Also, as expected, higher values of VT lead to 

higher values of DW. In Figure D–4, as was also shown in Figure D–1, α almost solely controls the DR

values. The slopes are relatively flat for all other Rankine vortex parameters. This general interpretation 

can be used for all interaction plots, including for Figure D–5, which shows the distance (‘–’ for south, 

‘+‘ for north, in miles) from the convergence line where estimated tree fall direction (β) was 90 degrees 

and 180 degrees. 

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

0

2

4

6

8

10

12

Damage Width (DW) Number

1 1.5 2 2.5 3 3.5 4

0

2

4

6

8

10

12

Damage Ratio (DR) Number

Figure D–2. Histograms showing 

values of DW and DR for X = 2.1 miles. 

382 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

Appendix D 

© 2011 GeoEye. 

Used with permission. 

Enhancements by NIST 

Figure D–3. Area and grid point for detailed factorial design. 

NIST NCSTAR 3, Joplin Tornado Investigation 383 
 

 

 

Appendix D 

Figure D–4. Interaction effects plots for DW (top) and DR (bottom) 

for X = 2.1 miles. 

384 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

Appendix D 

Figure D–5. Interaction effects plots for β = 90 degrees (top) 

and β = 180 degrees (bottom) for X = 2.1 miles. 

NIST NCSTAR 3, Joplin Tornado Investigation 385 
 

Appendix D 

This page intentionally left blank. 

386 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

Appendix E 

MODELED WIND SPEED AND DIRECTION TIME HISTORIES AT SELECT
	

LOCATIONS 

Note: The best estimates of time histories for wind speed and direction from the tornado wind field model 

in this appendix are located nearest the center of the identified building. The complete set of modeled 

time histories will be available through the NIST Disaster and Failure Event Data Repository web site 

(http://www.nist.gov/el/disasterstudies/repository_home.cfm) when the Joplin Tornado Repository is 

completed. 

Figure E–1. Estimated time–history of wind speed and direction 

near the center of Walmart. 

NIST NCSTAR 3, Joplin Tornado Investigation 387 
 

 

Appendix E 

Figure E–2. Estimated time–history of wind speed and direction near the center of 

Franklin Technology Center. 

388 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

Appendix E 

Figure E–3. Estimated time–history of wind speed and direction 

near the center of Home Depot. 

NIST NCSTAR 3, Joplin Tornado Investigation 389 
 

 

 

 

Appendix E 

Figure E–4. Estimated time–history of wind speed and 

direction slightly east of the center of St. John’s Regional 

Medical Center (near the south end of the East Tower). 

390 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

Appendix E 

Figure E–5. Estimated time–history of wind speed and direction 

near the center of Joplin East Middle School. 

NIST NCSTAR 3, Joplin Tornado Investigation 391 
 

 

 

Appendix E 

Figure E–6. Estimated time–history of wind speed and direction 

near the center of Joplin High School. 

392 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

Appendix F 

TORNADOES PER YEAR MAPS (EF–0 THROUGH EF–5) 

The values on the maps in this appendix represent the average number of tornado touchdowns of the 

indicated EF intensity per year that occurred within an 80–mile radius of each grid point (values are 

centered over grid point locations). This average is for the period of 1950 through 2011, and was 

constructed using data from the official record of tornado touchdown locations.191 If no value appears on 

the grid, the average number of tornado touchdowns per year is close to zero in that area. 

Figure F–1. Map of EF–0 tornadoes per year. 

191 NOAA (http://www.spc.noaa.gov/wcm/data/1950–2012_torn.csv). 

NIST NCSTAR 3, Joplin Tornado Investigation 393 
 

 

 

 

Appendix F 

Figure F–2. Map of EF–1 tornadoes per year. 

Figure F–3. Map of EF–2 tornadoes per year. 

394 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

Appendix F 

Figure F–4. Map of EF–3 tornadoes per year. 

Figure F–5. Map of EF–4 tornadoes per year. 

NIST NCSTAR 3, Joplin Tornado Investigation 395 
 

 

 

Appendix F 

Figure F–6. Map of EF–5 tornadoes per year. 

396 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 192

 

 

 

Appendix G 

HISTORY OF CODE ADOPTIONS BY THE CITY OF JOPLIN 

Table G–1. City of Joplin Code Adoptions188 

192 © 2008 City of Joplin. Used with Permission. 

NIST NCSTAR 3, Joplin Tornado Investigation 397 
 

Appendix G 

398 NIST NCSTAR 3, Joplin Tornado Investigation 
 

Appendix G 

NIST NCSTAR 3, Joplin Tornado Investigation 399 
 

Appendix G 

400 NIST NCSTAR 3, Joplin Tornado Investigation 
 

Appendix G 

NIST NCSTAR 3, Joplin Tornado Investigation 401 
 

Appendix G 

This page intentionally left blank. 

NIST NCSTAR 3, Joplin Tornado Investigation 402 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Appendix H 

ESTIMATED DESIGN WIND PRESSURE AND STRENGTHS OF 

CONNECTIONS OF JOPLIN WALMART BUILDING #59
	

H.1 ESTIMATED DESIGN WIND PRESSURE BASED ON IBC 2000 

 Basic design wind speed: V = 90 mph (3 s gust)
 

 Exposure category: C
 

 Building parameters:
 

- Low–rise, 290 ft  573 ft in plan, with mean roof height h = 21.33 ft and 2 ft parapet 

- Gust–effect factor: G = 0.85 (rigid building) 

- Partially enclosed193 . Internal pressure coefficient GCpi = ± 0.55 

 Importance factor: I = 1.15194 

 Topographic factor: Kzt = 1.0 (flat terrain) 

The worst–case net design wind pressure for the Walmart building, based on above parameters and design 

procedure of IBC 2000, is wind perpendicular to the building’s length (N–S axis). The computed net 

internal pressure (with + GCpi) and net internal suction (with – GCpi) are shown in Table H–1. 

Table H–1. Net internal pressure and internal suction for the Walmart building. 

Surface Z (ft) q (psf) CP qGCP (psf) 

Net Pressure (psf) with 

+ GCpi – GCpi 

Windward 0 – 15 20.27 0.8 13.78 1.83 25.73 

20 21.47 0.8 14.6 2.65 26.55 

21.3 21.72 0.8 14.77 2.82 26.72 

Leeward All 21.72 –0.5 –9.23 –21.18 2.72 

Side wall All 21.72 –0.7 –12.92 –24.87 –0.97 

Roof 0 – 21.3 21.72 –0.9 –16.62 –28.6 –4.67 

21.3 – 42.6 21.72 –0.5 –9.23 –21.2 2.72 

42.6 – 290 21.72 –0.3 –5.54 –17.5 6.4 

193 Assumed based on the conditions where the building envelope was breached during the tornado 

194 Not specified on design drawings obtained by NIST. Assumed based on Occupancy Category III (Buildings and other structures 

where more than 300 people congregate in one area) 

NIST NCSTAR 3, Joplin Tornado Investigation 403 
 

 

 

 

 

 

 

 

 

 

Appendix H 

Wind pressure distribution corresponding to the net internal pressure case (+ GCpi), shown below in Fig. 

H–1, represents the worst load case for wind uplift, with estimated maximum design (code–level) net 

uplift pressure of 28.6 lb/ft2 (psf) on the roof. 

21.2 psf 

17.5 psf 

21.2 psf 

28.6 psf 

2.8 psf 

2.6 psf 

1.8 psf 

21.3’

42.6’

Front Wall (west) Rear Wall (east) 

290’

Key: psf, pounds per square foot (lb/ft2). 

Figure H–1. Wind pressure distribution for the Walmart building. 

H.2	 ESTIMATED UPLIFT STRENGTH OF ROOF JOIST–TO–JOIST GIRDER 

CONNECTIONS 

 Roof joist is welded on each end to joist girder by 2 3/16 in.  11⁄2 in. (weld leg size w  weld 

length l) fillet welds, E70 electrode 

 Design strength per 1/16 in. of fillet weld leg per inch of weld length: 

= 0.75(0.6FEXX)(0.707wl) = 1.392 kips/in. 

 Uplift capacity for 6 in. of total weld length l (3 in. on each end) and 3/16 in. weld leg size: 

= (1.392 kips/in.)(3)(6) = 25.05 kips 

 Tributary roof deck area supported by each roof joist: = 39 ft  5 ft 71⁄2 in. = 219.4 ft2 

 Estimated uplift strength of joist–to–girder connections: 25,056 lb/219.4 ft2 = 114 lb/ft2 

404 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

Appendix I 

ESTIMATED DESIGN WIND PRESSURE AND STRENGTHS OF 

CONNECTIONS OF JOPLIN HOME DEPOT BUILDING
	

I.1 ESTIMATED DESIGN WIND PRESSURE BASED ON BOCA NBC/1996 

 Basic design wind speed: V = 90 mph (3 s gust)
 

 Exposure category: C
 

 Building parameters:
 

 Low–rise, one–story, 470 ft  250 ft in plan, with 28 ft mean roof height and 4 ft parapet 

 Gust–effect factor: G = 0.85 (rigid building) 

 Partially enclosed. Internal pressure coefficient GCpi = ± 0.25 

 Importance factor: I = 1.15195 

Design Wind Pressure for MWFRS: 

Basic velocity pressure: PV = 0.00256V2 = 20.7 lb/ft2 . Assume Condition I enclosure: GCPi = ± 0.25 (see 

BOCA NBC/1996). The computed net internal pressure and internal suction based on BOCA NBC/1996 

for the MWFRS of Home Depot building is shown below in Table I–1. 

The wind pressure distribution corresponding to the net internal pressure case, shown in Fig. I–1, 

represents the worst load case for wind uplift, with code–level net uplift pressure of 26.2 lb/ft2 (psf) on the 

roof. Note – this calculated value is slightly less than the design uplift pressure of 28.2 psf indicated on 

the structural drawings of the Home Depot. This confirms that the wind uplift pressure used in designing 

the Home Depot was in conformance with (and slightly exceeding) the requirement of the building code 

in effect (BOCA NBC/1996). 

Design Wind Pressure for Component and Cladding: 

For BTS building, the roof system is an integral part of the MWFRS, not just cladding. Thus the 

estimated design wind pressure computed above for MWFRS that pertains to the roof could arguably be 

used for designing the roof. However, treating the roof as component and cladding could yield higher 

design wind pressure acting on the roof deck panels and the fasteners (puddle welds). The following 

195 Assumed by NIST for this estimation based on Table 1609.5 Importance Factor (I) of BOCA NBC/1996. Design drawing 

obtained by NIST indicated a Wind Load Importance Factor I = 1.33 was used. However, this value was inconsistent with value 

specified by BOCA NBC/1996. 

NIST NCSTAR 3, Joplin Tornado Investigation 405 
 

 

 

 

 

 

’

Appendix I 

Table I–1. Net internal pressure and internal suction for MWFRS of the Home Depot 

building. 

Surface Z 

(ft) Gh Kz CP PVIKhCPGh PVIKhGCPi 

Net Pressure (psf) 

with 

Internal 

Pressure 

Internal 

Suction 

Windward 0 –

15 

1.264 0.8 0.8 19.26 ± 5.77 13.5 25.0 

20 1.264 0.87 0.8 20.95 ± 5.77 15.2 26.7 

25 1.264 0.93 0.8 22.38 ± 5.77 16.6 28.2 

28 1.264 0.97 0.8 23.33 ± 5.77 17.6 29.1 

30 1.264 0.98 0.8 23.57 ± 5.77 17.8 29.3 

33 1.264 1.01 0.8 24.33 ± 5.77 18.6 30.1 

Leeward All 1.264 0.97 –0.5 –14.58 ± 5.77 –20.4 –8.8 

Side wall All 1.264 0.97 –0.7 –20.42 ± 5.77 –26.2 –14.7 

Roof All 1.264 0.97 -0.7 –20.42 ± 5.77 –26.2 –14.7 

28’

15 

5’

5’

5’ MRH 2’

250’

26.2 psf 

20.4 psf 

13.5 psf 

15.2 psf 

16.6 psf 

17.8 psf 

18.6 psf 

Figure I–1. Wind pressure distribution for MWFRS of the Home Depot building. 

calculation estimates the code–level net uplift pressures, based on BOCA NBC/1996, on the roof deck 

panels and the fasterners if they are considered as component and cladding. 

P = PVIKh[(GCp) – (GCpi)] 

Where, 

PVIKh = 23.09 psf (see above and Table I.1), 

406 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

I.2 

Appendix I 

GCpi = ± 0.25, and 

GCp computed below based on effective wind areas of roof deck panel and tributary area of each fastener 

(puddle weld): 

	 Effective wind areas:
 

‒ Roof deck panel: A = 3 ft  5.375 ft = 16.124 ft2
 

‒ Fasterner (36/4 pattern): A = 5.8 ft  1.0 ft = 5.8 ft2
 

	 Roof coefficient (GCp): 

Component A (sq.ft) 

Zone 1 

GCp 

196 

Zone 2 

Roof deck panel 16.125 –1.38 –2.54 

Fastener 5.8 –1.4 –2.6 

 Net roof component pressures, psf 

Component 

Net Uplift Pressure 

Zone 1 Zone 2 

Roof deck panel 

Fastener 

–37.6 

–38.1 

–64.4 

–65.8 

ROOF BRACING FORCES RT 

Force transferred to roof from lateral pressure on 

exterior of windward wall: 

Equating moments at base of wall (wall extends 2 ft below 

ground on top of footing): 

Zone 3 is treated as Zone 2 due to the 4–foot height parapet (greater than 3 ft) 

ୀଽ௿஘ (ାୀயୂ)(ାୂ) (

଀଄ ൅ ି) ൅ (ାୂயି)(ୂ) (଄ ൅ ାୄ) ଁ ଁ 

൅(ାୃயୃ)(ୂ) (

଄ ൅ ିି) ൅ (ାୄய୅)(ୂ) (଄ ൅ ିୄ) ଁ ଁ 

ି 

൅ (ା୅யୃ)(ି)( ൅ ୀଽ) ି 

 ௿஘ ୀଽୄயା ଗଓ଍ ୎୙ଡ଼୛୔ ୟଡ଼ଡ଼୓ 

28’

15’

5’

5’

5’

2’

MRH 

13.5 psf 

15.2 psf 

16.6 psf 

17.8 psf 

18.6 psf 

2’

R T 

NIST NCSTAR 3, Joplin Tornado Investigation 407 

196 
 

 

 

 

 

 

 

 

 

 

 

 

Appendix I 

Force transferred to roof from uniform pressure on 

leeward wall: 

ୀି 

ୀଽ௿஘ (െାୁயୃ)(ୀି)( ି ൅ ି) 

 ௿஘ െିୄ୆ய୆ ଗଓ଍ ଈଓଖକ଎ ଙଖଖ଍ 28’ 32’

MRH 14.6 psf 

2’

R T 

Force transferred to roof from uniform internal pressures on 

leeward wall: 

ି୅ 

ୀଽ௿஘ (േୂயୄୄ)(ି୅)( ൅ ି) ି
L

 ௿஘ േ୅ୃயି plf along roof
 

± 5.77 psf 

28’

2’

R T 

Net force RT per foot transferred to roof due to lateral wind load: 

With internal suction:
 

Windward: RT = 307.1 + 86.2 = 393.3 plf
 

Leeward: RT = –279.9 + 86.2 = –193.8 plf
 

 Net design roof bracing force due to lateral wind loads: W = 393.3 + 193.8 = 587.1 plf 

408 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

I.3 

Appendix I 

ROOF DIAPHRAGM SHEAR AND STIFFNESS 

Diaphragm Shear: 

Design diaphragm shear force: 

R = (L/2)(W) = 470  1⁄2  587.1 = 

137,968.5 lb
 

Required nominal unit shear at side walls 

(design diaphragm shear): 

S = R/B = 137,968.5/250 = 552 plf 

Note: This calculated roof diaphragm shear 

value of 552 plf confirms the design diaphragm 

shear value of 560 plf shown on the Home Depot design drawings. 

Diaphragm Shear Stiffness G’: 

Roof diaphragm shear stiffness G ’ is a function of roof deck type and size, support joist spacing, and 

fastener types and pattern. For the Home Depot: 

 Roof deck: B, 1.5 in.  22–gauge wide–rib, 36 in. width, three–span continuous 

 Joist spacing LV: Varied from 5.4 ft to 5.8 ft (Note: This conforms to FM Global’s 

recommended span of ≤ 6 ft for 22–gauge roof deck) 

 Fasteners: 

 At support: 5/8 in.– puddle welds, 36/4 pattern 

 Side laps: #10 Buildex screws, 7 per span 

G ’

, based on SDI Deck Diaphragm Design Manual (2nd Edition) and CMC Joist and Deck Tables, for 5/8 

in.– puddle weld with 36/4 weld pattern and #10 Buildex screws side laps connection: 

௸ଁ ௴ ଽயୀ௱௫௫ ୀயୄ୅ ൅ ൅ ୀ௸଀ ௹ச ௹ச 

Where: 

K2 = 29,500t = 29,500(0.0295) = 870 (t : deck thickness = 0.0295 in. for 22–gauge deck) 

Dxx = Deck warping factor, dependent on fastener pattern at supports = 1072 (for 36/4 pattern) 

K1 = 0.181 (factor relates to slip coefficient) 

L=470’

B=250’

W = 587.1 plf 

NIST NCSTAR 3, Joplin Tornado Investigation 409 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I.4 

Appendix I 

୅ୄଽ 

௴ ାୀய୆ ଒ோଐକ ଽயୀଟାଽୄି ୀயୄ୅ ൅ ൅ ୀଟଽயା୅ାଟୂய୅ ୂய୅ 

Note: 6.7 k/in.  G ’ = 13.9 k/in.  15 k/in.  the Home Depot roof is a flexible roof diaphragm based 

on ACI 551 roof shear stiffness classifications. 

Roof diaphragm maximum shear deflection due to code–level shear force: 

଄௹ଁ (ୂ୅ୄயା)(ୁୄଽ)ଁ 

ஊஇஐ ୁயୄ ଐକଊଏ ୅௴ ௯ ୅(ାୀய୆)ାଽଂ(ିୂଽ) 

UPLIFT AND SHEAR CAPACITIES OF ROOF DECK–TO–JOIST 

CONNECTIONS 

Strength based on uplift alone: 

ASD governing load combination for net uplift force acting on deck–to–joist connection: 

0.6D + W 

Where: 

D = 16 psf (service dead load shown on the Home Depot design drawings) 

W = –26.2 psf (service wind uplift load computed above based on BOCA NBC/1996) 

Required uplift resistance (or required tensile strength) of puddle welds, T, at service load: 

T = LV(0.6D + W)(1.1) = (5.8)[(0.6)(16) – 26.2](1.1) = –105.9 plf 

Nominal uplift resistance per foot along roof of puddle welds, Tn, based on 36/4 weld pattern, 5/8 in.–

puddle weld, and 5.8 ft span length: 

଒௽ ଒௽ 

ଁ஬ ଂଟ௹௩ ௰௹௩ 

ଟ௹௩ ௰ 

Where: 

K = 2.7 (for 36/4 weld pattern, based on SDI Deck Diaphragm Design Manual, 2nd Edition)
 

C = 3 ft (width of roof deck)
 

P = 0.28t(d–t)Fu) (Nominal uplift resistance per puddle weld, per AWS D1.3/D1.3M–2008–
 

Structural Welding Code – Sheet Steel)
 

t = 0.0295 in. (thickness of 22–gauge metal roof deck)
 

d = 5/8 in. (weld diameter)
 

Fu = 55 ksi 

410 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

Appendix I 

଄ ன஧௣  ௽ ଽயି୅ଟଽயଽି୆ୂଟ ( െ ଽயଽି୆ୂ) ଟୂୂ ଽயିୄୀ ିୄୀ ଓଉଚ ଗଌଙ ଞଌଓଋ, ଇ ௪ணப஢ 

Thus, 

ୀயୄଟିୄୀ 

ଁ஬ ୀୀୃயୄ ଗଓ଍ ୀயଽ 

Safety factor for uplift strength of puddle weld: 

ଁ஬ ୀୀୃயୄ ௨ ୀயି ିயୂ ଙଌଘଜଐଙଌଋ ଧ ௼௸ ଍ଖଙ ଜଗଓଐ଍ଛ ଈଓଖକଌ ଁ ାଽୂய୆ 

Nominal uplift capacity of roof–deck–to–joist connection: 

ଁ஬ ୀୀୃயୄ ଗଓ଍ ଂ஬ ୃିயୃ ଗଚ଍ ௹௩ ୂயୀୄୂ ଍ଛ 

Note: 

The 62.6 psf uplift capacity of the roof–deck–to–joist connection exceeds the design uplift pressure of 

26.2 psf by a safety factor of 2.4. This means a code–level uplift pressure would not have caused the 

failure of the roof–deck–to–joist connections (or the disconnection of the metal roof deck panels). 

Strength based on combined uplift and shear: 

ASD shear and tension interaction equation for support fasteners (puddle welds): 

଀ய଄ ௾த ௨௦ட஠பண 

଀ய଄ 

௨ଁ ( ) ൅ ( ) ାயଽ ௾த ஬௢ ௨௣ப஧த௧ ଁ஬ 

Where: 

u = 2.5 (safety factor for weld in tension) 

T = 105.9 plf (above) 

Tn = 1,800.7 plf (above) 

Qf no uplift = 2,010 lb (nominal shear strength per 5/8 in.– puddle weld (tabulated in SDI manual and 

CDC Tables) 

Qf usable : Available nominal shear strength of puddle weld in the presence of an uplift force: 

଀ய଄ ௿யଅଆ ଀ய଄ ௿யଅଆ 

௨ଁ ିயୂଟାଽୂய୆ 

௾த ௨௦ட஠பண (ାயଽ െ ( ) ) ଟ௾த ஬௢ ௨௣ப஧த௧ (ାயଽ െ ( ) ) ଟ ିଽାଽ ା୆ୀୀயୁ ଓଉଚ ଁ஬ ା୅ଽଽயୄ 

NIST NCSTAR 3, Joplin Tornado Investigation 411 
 

 

 

 

 

 

 

 

  

 

 

 

Appendix I 

Required nominal unit shear at side walls: 

Sn required = 552 plf (from roof bracing forces calculation above) 

Nominal shear strength Sn of type B 1.5 in.  36 in. wide–rib roof deck with 36/5 puddle weld pattern 

based on the SDI Deck Diaphragm Manual and CMC Joist and Deck Tables: 

For 5.5 ft deck span  Sn = 1,318 plf 

For 6.0 ft deck span  Sn = 1,230 plf 

Thus for LV = 5.8 ft deck span  Sn = 1318 – (1318 –1230)(0.3/0.5) = 1265.2 plf 

Available nominal deck shear strength adjusted for presence of uplift (accounting for effect of shear and 

tension interaction): 

଀஬ ட௩ட஧பட஠பண ଀஬ ( ௾த ௨௦ட஠பண 

௾த ஬௢ ௨௣ப஧த௧ ) ାିୃୂயି ( ା୆ୀୀயୁ 

ିଽାଽ ) ା஬ିାୄ ଗଓ଍ 

Factor of safety in combined shear and tension of deck–to–joist connection: 

଀஬ ட௩ட஧பட஠பண ାିାୄ

ିயି ିயୂ ଀஬ ௥ண௤௨஧௥ண஢ ୂୂି

Roof–deck–to–joist connection would not have failed under combined shear (lateral wind load) and 

tension (wind uplift) forces at code–level wind load. However, the safety factor is slightly less than is 

typically required for this design. 

412 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

J.1 

Appendix J 

ESTIMATED DESIGN WIND PRESSURE FOR JOPLIN EAST MIDDLE 

SCHOOL GYMNASIUM
	

DESIGN WIND PRESSURE BASED ON IBC 2000 

 Basic design wind speed: V = 90 mph (3 s gust)
 

 Exposure category: C
 

 Building parameters:
 

 Low–rise, with mean roof height h = 39.8 ft
 

 Arched roof; rise–to–span ratio r = 9 ft/102 ft = 0.9; Kd = 0.85
 

 102 ft  142.2 ft plan dimensions
 

 Gust–effect factor: G = 0.85 (rigid building) 

 Enclosed. Internal pressure coefficient GCpi = ± 0.18
 

 Importance factor: I = 1.0 

Net design wind pressure that corresponds to the wind parallel to ridge load case represents the worst 

design load case for wind uplift, with maximum design wind uplift pressure of 17.3 lb/ft2 (psf) acting on 

the roof system. Table J–1 and Fig. J–1 and J–2 summarize the wind pressure acting on the main wind–

force resisting system (MWFRS) of Joplin East Middle School’s gymnasium building based on the wind 

parallel to ridge load case. 

Table J–1. Wind pressure acting on the MWFRS of the Joplin East Middle School 

gymnasium. 

Surface Z (ft) q (psf) G CP qGCP (psf) Net Pressure (psf) with 

+ GCpi – GCpi 

Windward 0 – 15 15.0 0.85 0.8 10.2 6.9 13.5 

20 15.8 0.85 0.8 10.7 7.4 14.0 

25 16.5 0.85 0.8 11.2 7.9 14.5 

30 17.2 0.85 0.8 11.7 8.4 15.0 

35.3 17.8 0.85 0.8 12.1 8.8 15.4 

39.8 18.3 0.85 0.8 12.4 9.1 15.7 

44.3 18.7 0.85 0.8 12.7 9.4 16.0 

Leeward All 18.3 0.85 –0.42 –6.5 –9.8 –2.9 

NIST NCSTAR 3, Joplin Tornado Investigation 413 
 

 

 

 

 

Appendix J 

Surface Z (ft) q (psf) G CP qGCP (psf) Net Pressure (psf) with 

+ GCpi – GCpi 

Side wall All 18.3 0.85 –0.7 –10.9 –14.2 –7.3 

Roof 0 to h 18.3 0.85 –0.9 –14.0 –17.3 –10.4 

h to 2h 18.3 0.85 –0.5 –7.8 –11.1 –4.2 

2h 18.3 0.85 –0.3 –4.7 –8.0 –1.1 

8.4 psf 

7.4 psf 

9.8 psf 

8.0 psf 

11.1 psf 

17.3 psf 

9.4 psf 

9.1 psf 39.8’

79.6’

8.8 psf 

7.9 psf 

6.9 psf 

! 

142.2’

Front Wall (west) Rear Wall (east) 

! 

Figure J–1. Wind pressure distribution along length of the Joplin East Middle School
 

Gymnasium.
 

17.3 psf 

14.2 psf 

102 

14.2 psf 

Section !–!
	

Figure J– 2. Wind pressure distribution on the cross section of the Joplin East Middle
 

School Gymnasium.
 

414 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

Appendix K 

QUALITATIVE ANALYSIS OF THE CURRENT STATE OF TORNADO 

WARNING SYSTEMS IN THE U.S.
	

Throughout the United States, many cities have siren–based communication systems to alert residents and 

visitors about emergencies that require immediate action (also known as rapid–onset events). The most 

common use of the sirens is to alert people of severe weather or tornadoes in the vicinity; however, they 

can be used to alert or warn citizens of many different types of disasters, including severe weather, 

chemical emergencies, HAZMAT spills, national security attacks, floods, fires, or other types of 

emergencies. 

An assessment of more than 75 U.S. counties, cities, and towns was conducted to identify the similarities 

and differences among siren systems from community to community. An Internet search was conducted 

to identify at least one community from each tornado–prone State that used a siren system to alert of 

emergencies. Table K– 1 shows the number of counties, cities, or towns reviewed from each State; and 

although some communities from east and west coast States were assessed, the focus of this assessment 

was on States located in the tornado–prone region of the Midwestern United States commonly referred to 

as “tornado alley.” There was no systematic method for choosing communities; instead, communities

were chosen for this assessment if they provided emergency communications procedures on a website that 

was accessible to the public. 

The assessment showed that emergency information about tornadoes is disseminated via siren systems 

using a variety of methods before the tornado hits. The main differences found among these 76 

communities pertained to siren usage (i.e., the types of emergencies that the sirens were used for), 

activation procedures, sounding patterns, and the guidance provided to the public on how to respond to 

siren soundings. 

While some communities were found to use their sirens only for tornado emergencies, most of the 

sampled communities (59 out of 76) use their sirens for multiple types of events. Which types of 

emergencies the sirens are used for seems to be a decision made by each local community. Even 

jurisdictions that are adjacent to each other can use sirens for different types of emergencies. For 

example, Rankin County, Mississippi, sounds its sirens only for tornadoes, while adjacent Hinds County, 

Mississippi, sounds sirens for severe weather, national security events, and life–threatening situations that 

may impact the public (which are defined by the officials in charge of turning on the sirens). Problems 

with situational awareness may arise for residents who travel frequently between jurisdictions that use 

sirens differently. 

There are differences in siren activation procedures among communities as well. In the majority of 

communities sampled, sirens are activated if the National Weather Service (NWS) issues a warning for 

the area served by the sirens. Other communities have decided to rely mainly on local officials, trained 

tornado spotters, and/or a local emergency team for determinations about whether (and when) to activate 

the sirens. In some places, the fire or police department is in charge of sounding the sirens. 

NIST NCSTAR 3, Joplin Tornado Investigation 415 
 

 

 

Appendix K 

Table K– 1. The number of qualifying community emergency management 

websites chosen, by State. 

State 

No. of 

Sources State 

No. of 

Sources 

Alabama 3 Montana 

Alaska Nebraska 1 

Arizona Nevada 

Arkansas 2 New Hampshire 

California 1 New Jersey 

Colorado 3 New Mexico 1 

Connecticut New York 

Delaware North Carolina 

Florida 2 North Dakota 

Georgia 4 Ohio 4 

Hawaii 1 Oklahoma 5 

Idaho 1 Oregon 1 

Illinois 4 Pennsylvania 

Indiana 3 Rhode Island 

Iowa 4 South Carolina 

Kansas 3 South Dakota 

Kentucky 3 (5) Tennessee 3 

Louisiana Texas 4 

Maine Utah 1 

Maryland Vermont 

Massachusetts Virginia 

Michigan 2 Washington 1 

Minnesota 2 West Virginia 

Mississippi 4 Wisconsin 4 

Missouri 4 Wyoming 3 

The patterns of sounds used by siren systems also differ from community to community. While the 

majority of the 76 sampled locations did not provide publicly accessible online information about the 

lengths (in minutes) of their siren soundings, some did, and differences were found to exist even among 

this smaller sample. Some communities may sound the siren for a finite time interval, whereas others 

may sound the siren continuously using a repeating time interval. Using a finite time interval, a siren may 

sound for 3 min and then stop, regardless of when the emergency begins and ends. On the other hand, 

416 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

Appendix K 

when using a repeating time interval, a siren may sound for 3 min and turn off for 8 min, and repeat that 

pattern until the emergency is over. There is the potential for individuals familiar with a repeating time 

interval to become confused when visiting another community that uses a finite time interval pattern (and 

vice versa). 

There are also differing practices in regard to the types of sounds used. In some cases, the sound pattern 

differs based upon whether there is an actual emergency or the community is simply testing the system. 

In others, the community disseminates different sounds or tones to distinguish between types of 

emergencies; e.g., the tones are different for system tests versus hazmat warnings versus weather 

warnings. Plymouth, Minnesota, for example, uses a steady siren for tornadoes and a warble (or 

wavering) siren for all other emergencies. Finally, sirens may be set at differing volume levels, based 

upon spacing and the landscape, from community to community. 

Guidance provided to the public on how they should react when sirens are sounded varies across 

communities as well. In 10 of the 76 communities sampled, when a siren is sounded, individuals are 

supposed to turn to an information source, like a weather radio or news channel, to find more information. 

In 35 of the sampled communities, individuals are supposed to take cover and then tune into an 

emergency information source, like a weather radio or a local radio or television news station. However, 

only 18 of these 35 communities provide further guidance on what “taking cover” actually means. 

Generally, recommendations for “taking cover” state that if an individual is in a sturdy building, they

should immediately shelter in a basement, storm cellar, or a small interior room on the lowest level of the 

structure. The same recommendation is given for sheltering in schools, factories, or shopping centers. 

Also, it is generally recommended to stay away from glass. Five communities recommended that 

individuals should cover their head with a blanket or get under a table or mattress when sheltering in an 

interior room. Thirteen of the sampled communities give even more guidance on where to shelter; they 

instruct their residents to evacuate mobile homes and vehicles upon hearing the sirens sounded for a 

tornado and to go into a sturdy building. If there is no sturdy building available, people are instructed to 

lay flat in a ditch and cover their heads but beware of flash floods. 

Emergency communication issues can arise even within the same community. A city in Kentucky has 

both a siren and a public address system. Their intent is to use the siren to alert the public, and then to 

follow the alert with instructions on what to do via the public address system. This system provides a 

good example of how to structure alerts and warnings to prompt effective responses from the community 

before and during disasters. However, the problem is that the sirens can be heard throughout a half–mile 

radius, while the public address system can only be heard within a quarter–mile radius. This can cause 

confusion in the quarter–mile areas where people can hear a siren but not the public address system 

(www.lexingtonky.gov/index.aspx?page=1420). 

Of the 76 communities sampled, all of which had outdoor sirens, 42 stated specifically that the purpose of 

these sirens is to alert only persons located outdoors. None of the communities stated that their purpose is 

to alert people located indoors as well as outdoors. In Houston, Georgia, the sirens are placed only in 

areas where citizens are unlikely to hear any other warning, rather than all throughout the city. In 

Madison County, Alabama, the sirens can be heard by about 75 percent of the population, while in 

Louisville, Kentucky, 94 percent of the population can be reached with the sirens. Little Rock, Arkansas, 

states that its sirens are not intended to alert people who are indoors, whether or not they are sleeping, or 

who are in vehicles with the windows rolled up. 

NIST NCSTAR 3, Joplin Tornado Investigation 417 
 

Appendix K 

Overall, outdoor warning systems vary among communities within the United States, both within and 

outside of tornado–prone areas. Many communities, especially smaller towns and rural areas, even within 

tornado alley, do not have sirens. Additionally, there is significant variability in the design of tornado 

communication systems that can make it difficult to understand, from city to city and even within the 

same area, the information that they convey and how to appropriately respond. 

418 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

Appendix L 

U.S. CODES AND STANDARDS ON OUTDOOR WARNING SYSTEMS 

There are national model codes and standards applicable to outdoor siren–based communication systems 

for tornadoes (and other emergencies). A model code is a set of rules that is recommended for others to 

follow. A model code does not carry the force of law unless it is adopted. On the other hand, a standard 

is a technical document that contains more detailed description of how to measure, test, or satisfy the 

provisions of a particular code. As an example, a code may say that a community or a building must have 

an alarm system. The standard will provide more detailed information on how to meet the requirements 

of this code, including information about what kind of system must be installed and how the system must 

work (www.nfpa.org). 

The National Fire Protection Association’s (NFPA) National Fire Alarm and Signaling Code (NFPA 

72),197 essentially an installation standard, includes requirements for emergency communication systems, 

and can be applied to tornado siren systems. NFPA 72 contains a chapter (Chapter 24) specifically 

devoted to emergency communication systems (2013). This chapter establishes minimum requirements 

for the performance, reliability, and quality of installation for emergency communication systems. By 

definition, emergency communication systems are those that are intended to communicate information 

about emergencies, including (but not limited to) fires, accidents, and natural disasters. Chapter 24 

provides requirements for in–building communication systems, namely one–way in–building fire 

emergency voice/alarm communication systems, in–building mass notification systems, two–way radio 

communications enhancement systems (in buildings), area of refuge emergency communication systems 

(in buildings), and elevator emergency communication systems (in buildings). For the category that is 

most applicable to a community–wide tornado siren system, namely wide–area mass notification systems, 

NFPA 72 specifies requirements for the wide–area systems’ components, including the emergency

command center, high–power speaker arrays, high–power speaker array enclosures and mounting, and 

speaker array structural loads for wind– and seismic–resistant design. These wide-area mass notification 

systems are generally installed to provide real-time information to outdoor areas. 

NFPA 72 (2013) provides guidance on how to create and disseminate an emergency message, if the alert 

or warning system has that capacity. It suggests ways to improve intelligibility, the use of an alert tone in 

addition to a message, and the types of message content that will prompt a more efficient recipient 

response. This guidance is helpful for those communities with outdoor public address systems or visual 

signage; however, there is no mention of requirements for sound patterns, length of sounds, sound types, 

etc., or about the use of the siren system itself. 

All other current requirements that can be applied to tornado siren systems are standards. The first group 

of standards, listed below, focus on providing requirements for the construction, performance, and testing 

of the entire communication system. 

197 Even though NFPA 72 has been a code for a number of years, it is a referenced standard in the model fire codes and is often 

administered and enforced in that manner. 

NIST NCSTAR 3, Joplin Tornado Investigation 419 
 

 

 

 

 

 

 

 

 

 

 

 

Appendix L 

	 NFPA 1221 (2013), Standard for the Installation, Maintenance, and Use of Emergency Services 

Communication Systems (Chapter 14 on Public Alerting Systems) 

	 UL198 2017 (2011), Standard for General–Purpose Signaling Devices and Systems 

	 UL 1971 (2008), Standard for Signaling Devices for the Hearing Impaired 

	 IEC199 60849 (1998), Standard for Sound Systems for Emergency Purposes 

NFPA 1221, or the NFPA’s Standard for the Installation, Maintenance, and Use of Emergency Services 

Communication Systems has a chapter (Chapter 14) that focuses on public alerting systems. The standard 

states that such systems can be used to alert the public to natural or man–made events, including 

tornadoes. However, this standard provides very little in the way of requirements and even cites NFPA 

72 for requirements on the audible alarm. 

UL also has a standard on signaling devices intended for emergency or non–emergency use in both indoor 

and outdoor locations (UL 2017–2011), that can be applicable to tornado warning systems. The standard 

provides requirements for device construction and performance, as well as tests for evaluating the 

performance of particular components or capabilities. UL also has a standard on signaling devices for the 

hearing impaired (UL 1971–2008) that can be applicable to tornado warning systems. This standard 

covers the construction of the device’s enclosure, cover, ventilation openings, corrosion protection, 

insulating materials, mounting parts, operating mechanisms, and wiring, cables, connections, and circuit 

boards (i.e., mainly the construction of the device). The standard also provides requirements for the 

performance of the system by specifying a series of tests. Installation and operating instructions are 

included as well. 

Finally, IEC 60849 (1998) is another standard on sound systems for emergency purposes. The standard 

applies to sound reinforcement and distribution systems that are used to effect rapid mobilization of 

occupants in an indoor or outdoor area in an emergency. It specifies performance requirements for sound 

systems that use tone signals or voice announcements to broadcast information for the protection of lives. 

All four of these standards focus on requirements for designing and installing the notification system, 

without providing much in the way of requirements for system use (other than intelligibility 

measurements, which will be described below). These standards do not address how the device should be 

used to disseminate information, such as the types of emergencies for which the system should be used, 

system activation procedures, sounding patterns, or guidance that should be provided to the community 

about the system. 

Another group of standards, listed below, focus primarily on sound and intelligibility levels (including 

how to measure each): 

	 ANSI200 S1.13 (2010), Measurement of Sound Pressure Levels in Air 

	 ANSI S1.26 (2009), Method for the Calculation of Absorption of Sound by the Atmosphere 

198 Underwriters Laboratories.
 

199 International Electrotechnical Commission.
 

200 American National Standards Institute.
 

420 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

Appendix L 

	 ANSI S12.14 (2007), Methods for the Field Measurement of the Sound Output for Audible Public 

Warning Devices Installed at Fixed Locations Outdoors 

	 ANSI S3.2 (2009), Method for Measuring the Intelligibility of Speech over Communications 

Systems 

	 ISO201 9921 (2003), Ergonomic Assessment of Speech Communication 

	 ANSI S3.5 (1997), Methods for the Calculation of the Speech Intelligibility Index (SII) 

	 IEC 60268–16 (2011), Sound System Equipment (Part 16: Objective Rating of Speech 

Intelligibility by Speech Transmission Index
 

First, ANSI S1.13 (2010), Measurement of Sound Pressure Levels in Air, provides an objective way to 

measure sound pressure, or pressure fluctuations, in the air. The greater the amplitude of pressure 

fluctuation, the “louder” the sound will be perceived. This standard presents a method that relies solely

on physical parameters and not on subjective interpretation or opinion about volume. This relates 

specifically to emergency communication for tornadoes because it provides a standardized method of 

evaluating the performance of emergency sirens (i.e., whether the sound will reach specified areas of the 

community). 

Similarly, ANSI S1.26 (2009), Method for Calculation of the Absorption of Sound by the Atmosphere, 

provides a method of calculating atmospheric absorption losses of sound from any moving or stationary 

source for a range of meteorological conditions. This becomes especially useful when evaluating whether 

siren tones will reach desired areas under the types of weather conditions expected during tornadoes. 

The standard most relevant to tornado sirens is ANSI S12.14 (2007), Methods for the Field Measurement 

of the Sound Output for Audible Public Warning Devices Installed at Fixed Locations Outdoors. This 

standard provides procedures for measuring and reporting certain properties of sounds produced by 

audible public warning devices. ANSI S12.14 can be used, for example, by customers of public warning 

devices to verify the compliance of their systems with specific sound output specifications. 

The last four standards listed above all relate to measuring or assessing speech intelligibility, i.e., the 

capability of being understood, comprehensible, and clear (NFPA 2010). Intelligibility measurements 

apply to mass communication or siren systems that allow for the dissemination of voice messages. ANSI 

S3.2 (2009), Method for Measuring the Intelligibility of Speech over Communication Systems, presents a 

standardized method for evaluating the intelligibility of a voice communication system. This method 

involves comparing the monosyllabic words trained listeners receive (and identify) with the words trained 

talkers or speech coders speak into a communication system. The communication system connects the 

talkers with the listeners, all of whom are required to be native speakers of English and have no speech or 

hearing defects. ISO 9921 (2003), Ergonomic Assessment of Speech Communication, standardizes 

ergonomic assessment of speech communication by recommending levels of speech–communication 

quality required for conveying messages in different applications, including when warning of a hazard or 

danger. Referenced within ISO 9921 are terms known as the “speech intelligibility index” and “speech 

transmission index.” Both refer to objective measures for predicting the intelligibility of speech. ANSI

201 International Organization for Standardization. 

NIST NCSTAR 3, Joplin Tornado Investigation 421 
 

 

 

 

Appendix L 

recently updated its standard on one method, which is now entitled ANSI S3.5 (1997), Methods for the 

Calculation of the Speech Intelligibility Index (SII), and the IEC also updated their standard on a different 

method, which is referred to as IEC 60268, Part 16, “Objective Rating of Speech Intelligibility by Speech 

Transmission Index.”

There are also standards that are devoted to the individual physical components that make up 

communication systems. Two examples follow: 

	 UL 1480 (2010), Standard for Speakers for Fire Alarm, Emergency, and Commercial and 

Professional Use 

	 UL 1989 (2010), Standard for Standby Batteries 

The one most specific to emergency communication is UL 1480 (2010), Standard for Speakers for Fire 

Alarm, Emergency, and Commercial and Professional Use. This standard lists requirements for the 

construction of these types of speakers as well as various types of speaker performance tests. Similar 

standards are available for other components of communication systems, such as the UL 1989 (2010) 

standard on standby batteries. 

In sum, no national codes or standards exist to provide requirements or standardization on the ways in 

which outdoor tornado siren systems should be used to disseminate emergency communications before or 

during tornadoes. Instead, as indicated above, current codes and standards focus on the construction, 

performance, and testing of the physical components of such systems. NFPA 72 has begun to provide 

guidance on the types of messages that should be disseminated via wide–area voice communication 

systems (typically used in communities); however, this guidance does not assist those communities that 

must rely on tone–based sirens (i.e., systems without the ability to send public address announcements). 

422 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

Appendix M 

NOAA/NWS WARNING TEXT FOR THE JOPLIN TORNADO 

M.1 WARNING ISSUED AT 5:09 PM CDT 

WFUS53 KSGF 222209
 

TORSGF
 

MOC097–222300–
 

/O.NEW.KSGF.TO.W.0030.110522T2209Z–110522T2300Z/
 

BULLETIN – EAS ACTIVATION REQUESTED
 

TORNADO WARNING
 

NATIONAL WEATHER SERVICE SPRINGFIELD MO
 

509 PM CDT SUN MAY 22 2011 

THE NATIONAL WEATHER SERVICE IN SPRINGFIELD HAS ISSUED A
 

* TORNADO WARNING FOR... 

WESTERN JASPER COUNTY IN SOUTHWEST MISSOURI... 

* UNTIL 600 PM CDT. 

* AT 505 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A TORNADO 10 MILES WEST OF 

CARL JUNCTION...OR 6 MILES EAST OF COLUMBUS...MOVING EAST AT 30 MPH. THIS STORM HAS A HISTORY OF 

PRODUCING FUNNEL CLOUDS AND TENNIS BALL SIZE HAIL. 

*	 LOCATIONS IMPACTED INCLUDE AIRPORT DRIVE...ALBA...ASBURY...ATLAS...BROOKLYN HEIGHTS...CARL 

JUNCTION...CARTERVILLE...LAKESIDE...NECK CITY...NORTHEASTERN JOPLIN...OAKLAND P!RK/ORONOGO/

PURCELL...WACO AND WEBB CITY. 

NIST NCSTAR 3, Joplin Tornado Investigation 423 
 

 

 

 

 

 

Appendix M 

INTERSTATE 44 BETWEEN MILE MARKERS 13 AND 18 WILL ALSO BE IMPACTED BY THIS TORNADO. 

IN ADDITION TO A TORNADO...THIS STORM IS CAPABLE OF PRODUCING LARGE DAMAGING HAIL UP TO TENNIS 

BALL SIZE. 

PRECAUTIONARY/PREPAREDNESS ACTIONS... 

THE SAFEST PLACE TO BE DURING A TORNADO IS IN A BASEMENT. GET UNDER A WORKBENCH OR OTHER PIECE OF 

STURDY FURNITURE. IF NO BASEMENT IS AVAILABLE...SEEK SHELTER ON THE LOWEST FLOOR OF THE BUILDING IN 

AN INTERIOR HALLWAY OR ROOM SUCH AS A CLOSET. USE BLANKETS OR PILLOWS TO COVER YOUR BODY AND 

ALWAYS STAY AWAY FROM WINDOWS. 

IF IN MOBILE HOMES OR VEHICLES...EVACUATE THEM AND GET INSIDE A SUBSTANTIAL SHELTER. IF NO SHELTER IS 

AVAILABLE...LIE FLAT IN THE NEAREST DITCH OR OTHER LOW SPOT AND COVER YOUR HEAD WITH YOUR HANDS. 

&& 

LAT...LON 3733 9461 3735 9436 3708 9430 3711 9462 3720 9462 

TIME...MOT...LOC 2208Z 260DEG 26KT 3716 9472 

HAIL 2.50IN 

$$ 

WISE 

M.2 WARNING ISSUED AT 5:17 PM CDT 

WFUS53 KSGF 222217
 

TORSGF
 

KSC021–MOC097–145–222300–
 

/O.NEW.KSGF.TO.W.0031.110522T2217Z–110522T2300Z/
 

BULLETIN – EAS ACTIVATION REQUESTED
 

424 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

 

 

 

 

 

Appendix M 

TORNADO WARNING 

NATIONAL WEATHER SERVICE SPRINGFIELD MO 

517 PM CDT SUN MAY 22 2011 

THE NATIONAL WEATHER SERVICE IN SPRINGFIELD HAS ISSUED A 

* TORNADO WARNING FOR... 

NORTHWESTERN NEWTON COUNTY IN SOUTHWEST MISSOURI/

SOUTHEASTERN CHEROKEE COUNTY IN SOUTHEAST KANSAS... 

SOUTHWESTERN JASPER COUNTY IN SOUTHWEST MISSOURI/

* UNTIL 600 PM CDT. 

* AT 514 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A TORNADO NEAR RIVERTON...OR 4 

MILES NORTH OF BAXTER SPRINGS...MOVING NORTHEAST AT 40 MPH. 

*	 LOCATIONS IMPACTED INCLUDE BAXTER SPRINGS...CLIFF VILLAGE...DENNIS !CRES/DI!MOND/DUENWEG/

DUQUESNE...FIDELITY...GALENA...IRON GATES...JOPLIN...LEAWOOD...LOWELL...REDINGS MILL...RIVERTON... 

SAGINAW...SHOAL CREEK DRIVE...SHOAL CREEK ESTATES...SHOAL CREEK ESTATE AND SILVER CREEK. 

INTERSTATE 44 BETWEEN MILE MARKERS 0 AND 13 WILL ALSO BE IMPACTED BY THIS TORNADO. 

IN ADDITION TO A TORNADO...THIS STORM IS CAPABLE OF PRODUCING LARGE DAMAGING HAIL UP TO GOLF BALL 

SIZE. 

THERE IS ADDITIONAL TORNADO WARNING FOR A SEPARATE STORM ACROSS CENTRAL AND NORTHERN JASPER 

COUNTY.
 

PRECAUTIONARY/PREPAREDNESS !CTIONS/
 

THE SAFEST PLACE TO BE DURING A TORNADO IS IN A BASEMENT. GET UNDER A WORKBENCH OR OTHER PIECE OF 

STURDY FURNITURE. IF NO BASEMENT IS AVAILABLE...SEEK SHELTER ON THE LOWEST FLOOR OF THE BUILDING IN 

AN INTERIOR HALLWAY OR ROOM SUCH AS A CLOSET. USE BLANKETS OR PILLOWS TO COVER YOUR BODY AND 

ALWAYS STAY AWAY FROM WINDOWS. 

IF IN MOBILE HOMES OR VEHICLES...EVACUATE THEM AND GET INSIDE A SUBSTANTIAL SHELTER. IF NO SHELTER IS 

AVAILABLE...LIE FLAT IN THE NEAREST DITCH OR OTHER LOW SPOT AND COVER YOUR HEAD WITH YOUR HANDS. 

&& 

NIST NCSTAR 3, Joplin Tornado Investigation 425 
 

Appendix M 

LAT...LON 3716 9479 3707 9426 3697 9430 3701 9479
 

TIME...MOT...LOC 2216Z 247DEG 36KT 3708 9470
 

HAIL 1.75IN
 

$$
 

WISE 

426 NIST NCSTAR 3, Joplin Tornado Investigation 
 

 

 

 

 

 

 

 

Appendix N 

METHODS FOR DEVELOPMENT OF EVIDENCE–BASED EXPLANATION 

OF DECISION–MAKING IN THE JOPLIN TORNADO
	

The main analysis technique used to develop an evidence–based explanation of decision–making in the 

Joplin tornado was the analysis method framework (Framework) originally developed by Ritchie and 

Spencer (1994). The Framework allows the analyst to classify and organize survivor data into themes, 

concepts, and categories (Ritchie, Spencer, and O’Connor 2003), which can later be developed into a 

model. 

This technique involved a four–step process: (1) data indexing, (2) data sorting, (3) data description, and 

(4) pattern detection. First, data indexing helps the analyst to organize or manage the data from interview 

transcripts. All interview transcripts were loaded into Atlas TI. Using a pre–developed code book 

(containing all categories and accompanying definitions that would be used to tag data later on in the 

process), analysts applied relevant codes (or data labels) to sections of text in each transcript (Richards 

and Richards 1994). 

The next step was to sort the data so that the text with similar content or properties was located together 

(Ritchie, Spencer, and O’Connor 2003). In order to complete this step, NIST analysts ran “queries” 

within Atlas TI that allowed them to capture all text on a particular code or set of codes from all 

interviews (or a particular set of interviews). What resulted from each query was a document that 

contained all of the original text from each interview that corresponded with the particular code or set of 

codes. 

Once the data were indexed and sorted, NIST analysts worked to describe the data. All data within a code 

or category were investigated to identify the range of the content and dimensions within the theme. In 

other words, the data within each main category was explored for axes of variation so that new, sub–

categories could be developed. Once the subcategories within each main category were fully developed, 

a Microsoft Excel spreadsheet was created to organize all of this new data. A new row was added for 

each interviewee and all of the columns associated with each person contained data for each main 

category and the associated subcategories. As the analyst combined and condensed the data using the 

subcategories, the data became more abstract in nature, and the subcategories could be used in the next 

stage of the analysis. 

The last stage in the Framework was pattern detection. This process allowed the analyst to find links and 

connections between two or more phenomena in the data (Ritchie, Spencer, and O’Connor 2003). During

pattern detection, the data in the spreadsheet were sorted by a variety of factors, including the types of 

cues perceived, the interpretations developed from these cues, and the actions taken in response to the 

storm. Each time a behavioral trend was identified among the codes, categories, or subcategories, the 

analyst developed diagrams and memorandums to document the trend. Within the memorandums, the 

analyst noted how the level of matching was distributed across the data by recording what percentages of 

the interviewees were involved in a given behavioral trend. As multiple trends were identified, they were 

combined into a larger diagram known as an evidence–based explanation of decision–making. A model 

NIST NCSTAR 3, Joplin Tornado Investigation 427 
 

 

 

Appendix N 

to depict this explanation was developed for the 2011 Joplin tornado (see Fig. 4–41 in Chapter 4). The 

model highlights the factors that influenced NIST interviewees (the sampled survivors, i.e., “decision–

makers”) to make decisions and take certain types of actions before the storm hit.

REFERENCES 

Richards, Lyn and Tom Richards. 1994. “From Filing Cabinet to Computer.” Pp. 146–172 in Analyzing 

Qualitative Data, edited by A. Bryman and R.G. Burgess. London: Routledge. 

Ritchie, Jane and Liz Spencer. 1994. “Qualitative Data Analysis for Applied Policy Research.” Pp. 173–

194 in Analyzing qualitative data, edited by A. Bryman and R. G. Burgess. New York, NY: 

Taylor & Francis. 

Ritchie, Jane, Liz Spencer, and William O’Connor. 2003. “Carrying out Qualitative Analysis.” Pp. 219–

262 in Qualitative Research Practice, A Guide for Social Science Students and Resarchers, edited 

by J. Ritchie and J. Lewis. Thousand Oaks, CA: Sage. 

428 NIST NCSTAR 3, Joplin Tornado Investigation