# Presentation: 033980

## Lesson 1:  Introducing the Enhanced Fujita Scale

- Dan McCarthy ( NWS SPC)
- and
- Jim LaDue (NWS WDTB)

**Notes:**
Welcome to the 1st of two lessons in the EF-Scale training.    Dan McCarthy and I will be introducing you to the Enhanced Fujita Scale.  Dan is the WCM of SPC and I am a meteorologist instructor at the WDTB.  This lesson is 31 slides long and should take up to 30 minutes to complete.  There are no prerequisites for this lesson.

## Goal and Scope of Training

- The Goal of this Training is to effectively integrate the EF-Scale into the post storm damage assessment.
- Two lessons, each followed by a quiz
- Comparison of the EF and F-Scale
- Using the EF-Scale to estimate tornado strength

**Notes:**
The goal of this training is to introduce you to using the Enhanced Fujita Scale (EF-Scale) in estimating tornado strength.  We are transitioning away from the F-Scale and so you need to know how the legacy F-Scale and the EF-Scale compare with each other.  There will be two lessons:  one is to compare the old with the new scales. The second is to actually rate damage with a few exercises.  Each lesson has a quiz at the end and a survey on the LMS. Complete both the quiz and the survey so that you get credit for taking them.  

## Motivation

- EF-Scale to be used by the NWS starting 01 Feb, 2007
- More complex than F-Scale

**Notes:**
You are seeing these lessons in advance of the planned implementation of the Enhanced Fujita Scale (EF-Scale) scheduled for 01 February 2007.  The two lessons you will be seeing will give you enough understanding of the EF-Scale to be able to start using it on damage surveys.  Everyone involved in participating in damage surveys in the NWS should be familiar with the content in these two lessons. The EF-Scale is complex involving many subtleties of building structure and failure modes within tornado events that lie outside the scope of this training.  We will provide you with a good starting point from which you can explore more about the EF-Scale.

## Lesson 1:  Learning Objectives

- Understand why the EF-Scale was created
- Identify the methodology in creating the EF-Scale.
- Understand the structure of the EF-Scale
- Identify differences between the EF- and F-Scale
- Understand the strengths of the EF-Scale
- Understand the limitations of the EF-Scale

**Notes:**
Here are the learning objectives for lesson 1.  First, you will take a tour on why and how the EF-Scale has been created.  This is important since you will see the methodology on how the wind speeds were selected for various degrees of damage for different damage indicators, or structures.  You’ll also need to calibrate yourself to the new scale, and in order to do that, we’ll show you what the differences are between the legacy F-scale and the current one. You will see some of the strengths of the EF-Scale.  And finally, you need to know that the EF-Scale does have some limitations so that you do not use it past it’s capabilities.

## Performance Objective

- Apply the strengths and limitations of the EF-Scale when rating damage produced by a tornado

**Notes:**
This performance objective applies to how you will use the information in this module to rating an actual tornado damage event.  At the end of this lesson, you should take away with you knowledge of the strengths and limitations of the EF-Scale and apply it to rating an actual tornado or other wind event.

## Why the EF-Scale was created

- Need more damage indicators
- recalibrate winds associated with F-scale ratings
- better correlate wind and rating
- account for construction variability
- Flexibility, Extensibility, Expandability

- Evidence indicates a well constructed house can be blown away by winds much less than 260 mph (Phan and Simiu,2003).

- Objectives:  1,  Why the EF-Scale?

- The framed house is one of only a few F-scale damage indicators.

**Notes:**
The NWS has been using the F-scale in the mid-late 1970s.  The original F-scale only contained an example of documented structures and their a description of expected damage for each rating from F0 to F5. Thus, one of the goals was to provide more damage indicators along with a series of pictures as examples.

Several studies also indicate that lower wind speeds could do F3 to F5 damage than was documented in the F-scale.  We needed to better correlate the degree of damage and the wind speed which includes the variability in construction quality.  Fujita realized in his memoirs “Mystery of Severe Storms” that it was necessary to include building descriptors in assessing tornado damage and acount for construction accountability.

While not changing the wind estimates, he did create a “modified” scale using a ‘little f’ for the type of building damaged in order to calculate ‘big F’ by the degree of that damage.

The EF-Scale to be implemented in the NWS is an extension of this idea but to many more types of structures.  Finally, we need a scale that can be changed so it has to have flexibility, extensibility, and expandability.  

## EF-Scale history:  Steering Committee

- Organize a Steering Committee (2001)

- Jim McDonald - TTU

- Joe Schaefer - SPC

- Brian Smith, NWS OAX

- Michael Riley - NIST

- Objectives:  2, Methodology

- Kishor Mehta -TTU

- Don Burgess – NSSL

**Notes:**
The Texas Tech University (TTU) Wind Science and Engineering (WISE) Research Center personnel recognized that a change to the rating system was needed.  They created an original steering committee that you see listed up here to generate a process to build a new rating system, namely the EF-Scale.  These people all have experience in engineering and the F-Scale.  Two of them worked with Fujita closely during parts of their careers, one has extensive research with storm damage and Doppler radar, another has extensive experience in developing and working with the current tornado database and one has vast knowledge of engineering and statistics.   There were a lot of issues to discuss and the steering committee decided that a forum (workshop) be organized and experts in various aspects of tornadoes be invited to this forum.

## The Steering Committee Organizes a Forum

**The Steering Committee Organizes a Forum**

- Led by Wind Science and Engineering Center, Texas Tech University, 7-8 March 2001
- Objectives
- Representative group of users
- ID key issues
- Make recommendations
- Develop a strategy

- Objectives:  2, Methodology

**Notes:**
In March of 2001, a forum was held in Grapevine, TX and 23 people attended.  As you can see, the forum participants represented a wide range of organizations and disciplines.   The objectives of the forum were 1) bring together a representative group of F-Scale users; 2) identify key issues; 3) make recommendations for a new/modified Fujita scale, and 4) develop a strategy for reaching consensus from a broad cross section of users.   

## The forum identifies EF-Scale development strategies

- Identify additional Damage Indicators (DI)s
- Correlate damage to wind speed
- Degrees of Damage (DOD) for each DI
- Preserve the historical database
- Seek input from users
- Maximize usability

- Objectives:  2, Methodology

**Notes:**
The forum participants met for a day and a half and set a plan in motion that would create the EF-Scale.  

The NWS personnel wanted many more damage descriptions and photographs. 

All the participants wanted to redefine  F-Scale wind speed ranges having a sliding scale to account for structural variablity.

They wanted to preserve and continue the historical database.

They wanted input from the field.  This will allow to keep the EF-Scale updated constantly.

Maximize its usability by having a PDA or available software so that the WCM or surveyor has the reference right at their fingertips.

They agreed upon the lexicon “D to redefine degree of Damage” (DOD) to identify what wind speed range would be required to produce describable damage for various DIs.  The forum wanted to make sure that there was continuity from all tornadoes rated with the F-scale to those to be rated with the EF-Scale.  Both scales would need to be correlated with each other.  The surveyors decided that the names of the F-Scale and the EF-Scale categories should be similar, i.e. F1 becomes EF1, F2 becomes EF2, etc.  Finally, good contacts with the user community are always a good idea as the development proceeded.  See McDonald and Mehta, 2001 for more details.

## EF-Scale Damage Indicators (DIs)

- 28 DIs were identified by the Steering Committee
- DIs and DODs can be added or modified
- Each DI has several Degrees of Damage (DOD)

- Objectives:  2,  methodology; 3, EF-Scale structure

- Framed house

- Single wide mobile home

- Small Retail Building

**Notes:**
The original steering committee, especially Dr. McDonald and Mehta of TTU, identified 28 Damage Indicators (DIs) based on their experience with tornado damage.  The framed house is one DI, a mobile home, and small retail buildings constitute other DIs.   Knowing that continued development of the EF-Scale is likely, more DIs can be added once the research on them have been done.  Or perhaps some Degrees of Damage (DODs) can be also be changed.           
	                                                                                                                   .
For each DI, the steering committee decided that the DOD should range from the initiation of damage all the way up to devastation of the structure.  

## 28 Damage Indicators

- Objectives:  3, EF-Scale structure

- Residences

- Commercial/retail structures

- Schools

- Professional buildings

- Metal buildings/canopies

- Towers/poles

- Vegetation

**Notes:**
Here are the 28 DIs.  They represent a wide variety of structures.  You could break them down into broad categories such as residences, commercial/retail structures, schools, professional buildings (including institutional buildings like universities and hospitals), metal buildings and canopies, and towers or poles.  Note that they’ve included a vegetation category, however we’ve only begun to study the relationship between wind speeds and crop damage.  No flying objects or crop damage have been included as a DI. The categorization of the DIs is not related to the strength of a building, hopefully the pictures can aid you in determining building strength.  This list of DIs is subject to modification as we improve the EF-Scale.

## Degrees of Damage

| DOD | Damage Description | EXP | LB | UB |
| --- | --- | --- | --- | --- |
| 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 or outward; 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 collapsed |  |  |  |
| 10 | Destruction of engineered and/or well constructed residence; slab swept clean |  |  |  |

**Degrees of Damage**

- DOD for a Framed House, FR12 or DOD2

- Objectives:  2,  methodology; 3, EF-Scale structure

**Notes:**
For each one of those DIs, there is a list of DODs where DOD1 starts with initiation of damage, and the highest DOD (10 for a framed house) is devastation or damage associated with an EF5 wind speed.  Intermediate DODs mostly represent increasingly more severe damage.  However, note that some consecutive DODs may indicate different aspects of building damage.  See that for DOD 2 the description is entirely about the roofing area while DOD 3 describes damage to glass exposed to the outdoors.  (It may be that the roof damage must occur as well as the broken windows.)

## Reason behind an upper and lower bound wind speed

- EXP:  Design exhibits typical construction

- Objectives:  2,  methodology; 3, EF-Scale structure

**Notes:**
The Lower Bound and Upper Bound values were devised by the appointment of six well-recognized experts selected for “Expert Elicitation.”  These people included 2 meteorologists, one who worked closely with Fujita another with extensive survey and Doppler radar experience; two engineers; an architect and one person who has degrees in meteorology and engineering and also has extensive tornado spotting and damage experience.  These experts met for a day-and-a-half in order to define wind speed estimates and ranges associated with the varied damage.

The range in wind speeds reflects the desire by the steering committee to account for variations in structure exposure and integrity.  The EXP, or Expected Wind Speed is really an average wind speed between the LB and the UB intended to be a typical wind speed required to do the damage labeled by a particular DOD.  For example with this DOD being a one, two family house, matching typical construction practices, you would experience damage associated with a particular DOD if it was subjected to an expected wind speed of that DOD.                                                                   

This is an example from 1-2 family residences.
(e.g., steel frame, reinforced concrete, strong load path)

## Reason behind an upper and lower bound wind speed (contd)

- EXP:  Design exhibits typical construction

- UB:  Design exceeds codes for typical US home, better than average load path.

- LB:  Design fails to meet US building codes, poor maintenance and/or load path

- Objectives:  2,  methodology; 3, EF-Scale structure

**Notes:**
If the house you’re inspecting fails to meet building codes (e.g., load path with just straight nailing, no clips, frame nailed to foundation), then you may only need a lower bound (LB) wind to do the damage for any particular DOD.  Contrarily, a well engineered house (e.g., load path reinforced with clips, framing properly bolted to foundation), like what you may find near some hurricane prone coastlines, may require an upper bound (UB) wind speed to match the DOD you see.  All these considerations eventually filter down to what rating you may give a structure.  You may also find that the more you know about structures and how the damage occurred, the more easily you’ll be able to rate a structure.  The fastest way to build up expertise besides experience is by talking with the experts and your peers to share ideas on how the structures in your area match with those in other areas.  More on this later.  

This is an example from 1-2 family residences.
(e.g., steel frame, reinforced concrete, strong load path)

## How the winds were derived for each DOD

- Possible Candidates
- Structural analysis to determine resistance and theoretical failure modes
- Simulation of tornado winds to produce structural damage
- Expert Elicitation
- Chosen method?
- Expert Elicitation

- Objectives: 2, EF-Scale methodology

- Chosen Experts:
- Greg Forbes – Meteorologist, TWC
- Don Burgess – Meteorologist, NSSL
- Doug Smith – Engineer, TTU
- Tim Reinhold – Engineer, Clemson University
- Tom Smith – Architect, Consultant
- Tim Marshall – Meteorologist/Engineer, Haag Engineers

**Notes:**
As it turns out, there are a host of methods to derive a wind speed estimate.  The Steering committee could’ve done a detailed structural analysis to determine resistance and failure pressures.  A large wind tunnel or perhaps a computer simulation to derive threshold wind speed to cause structural failure.  Or a method called expert elicitation could be done where experts are chosen to make the estimates.  Expert Elicitation is a method created by the Senior Seismic Hazard Assessment Committee (SSHAC, 1997) to estimate risk potential in seismic zones.  
The first two methods required more funding than was available to the Steering Committee.  Instead, they chose a more economical method of expert elicitation.  Texas Tech chose six experts in damage surveying to estimate the wind speeds.  The developers did have some idea of typical wind speeds through many years of experiments within the wind tunnel laboratory at Texas Tech.  

As time and resources permit, researchers may pursue one of the more rigorous methods of estimating wind speed.  It is also likely that better remote sensing of wind speeds in tornadoes may give us a better relation between 10 m, 3 second winds and building damage.

## Derive Wind Speeds by Expert Elicitation 

**Derive Wind Speeds by Expert Elicitation **

- Objectives: 2, EF-Scale methodology

- Describe the DIs and DODs and present to experts

- Train the experts in elicitation process

- Experts individually estimate wind speeds for each DOD

- Mehta and McDonald analyze results and present to experts for review

- Experts revise their wind speeds

- Iterate again

- Present final estimates to forum for review

**Notes:**
Here is what the TTU did.  First, they created detailed descriptions of each DI and DOD and then presented them to the experts.  

They trained the experts on how to elicit their estimates.  The DODs were given to the experts along with pictures where possible.  

The experts made the estimates, of expected, upper and lower bound winds. 

Then Drs Mehta and McDonald took the average and standard deviations of the expected, upper and lower bound winds and presented them back to the experts as part of round #1.   The DODs were arranged in order of increasing wind speed. 

 Round #2 involved the experts refining the wording of the DODs, and the expected, upper and lower bound winds and handing their elicitations back to Drs. Mehta and McDonald.  The process was repeated until fewer changes were made.  In this case, three rounds were all that were needed.  

Finally there is a peer review process where the original forum members commented on the results.

## Degrees of Damage

| DOD | Damage Description | EXP | LB | UB |
| --- | --- | --- | --- | --- |
| 1 | Threshold of visible damage | 63 | 53 | 80 |
| 2 | Loss of roof covering material (<20%), gutters and/or awning; loss of vinyl or metal siding  | 79 | 63 | 97 |
| 3 | Broken glass in doors and windows  | 96 | 79 | 114 |
| 4 | Uplift of roof deck and loss of significant roof covering material (>20%); collapse of chimney; garage doors collapse inward or outward; failure of porch or carport  | 97 | 81 | 116 |
| 5 | Entire house shifts off foundation  | 121 | 103 | 141 |
| 6 | Large sections of roof structure removed; most walls remain standing  | 122 | 104 | 142 |
| 7 | exterior walls collapsed  | 132 | 113 | 153 |
| 8 | Most walls collapsed except small interior rooms. | 152 | 127 | 178 |
| 9 | All walls collapsed | 170 | 142 | 198 |
| 10 | Destruction of engineered and/or well constructed residence; slab swept clean | 200 | 162 | 220 |

- Objectives:  3, EF-Scale structure

- Example DODs for a Framed House DI  (FR12 or DI2)

- Note some consecutive DODs have larger overlap than others

| DOD | Damage Description | EXP | LB | UB |
| --- | --- | --- | --- | --- |
| 1 | Threshold of visible damage | 63 | 53 | 80 |
| 2 | Loss of roof covering material (<20%), gutters and/or awning; loss of vinyl or metal siding  | 79 | 63 | 97 |
| 3 | Broken glass in doors and windows  | 96 | 79 | 114 |
| 4 | Uplift of roof deck and loss of significant roof covering material (>20%); collapse of chimney; garage doors collapse inward or outward; failure of porch or carport  | 97 | 81 | 116 |
| 5 | Entire house shifts off foundation  | 121 | 103 | 141 |
| 6 | Large sections of roof structure removed; most walls remain standing  | 122 | 104 | 142 |
| 7 | exterior walls collapsed  | 132 | 113 | 153 |
| 8 | Most walls collapsed except small interior rooms. | 152 | 127 | 178 |
| 9 | All walls collapsed | 170 | 142 | 198 |
| 10 | Destruction of engineered and/or well constructed residence; slab swept clean | 200 | 162 | 220 |

**Notes:**
Here’s an example of the results.  Again for 1-2 family residences, you can see that generally increasing DODs result in increasing winds.
But take note when you go from DOD3 to DOD4 (light colored boxes) the wind speeds don’t increase that much.  In DOD3, the threshold of breaking glass prompted the expert group to come up with an expected wind speed of 96 mph.  DOD4 (uplift of roof deck, collapse of chimney, failure of porch) is a different type of damage but the experts estimated the wind speeds similarly to DOD3.  But DOD5 prompted the experts to significantly increase the wind speeds.  

Note that DOD5 and DOD6  (darker colored boxes) are also very similar in wind speeds.  Does that mean if you have large sections of roof removed, but most walls remaining standing and the house still on the foundation that you have a DOD6?  It is conceivable to get that kind of damage and you wonder how you could achieve a rating.  Again, you may not see the progression of damage consistent with smaller DODs be evident.

This is an example from 1-2 family residences.

Each Damage Indicator (DI) has 3-12 levels to assess the Degree of Damage

## Degrees of Damage

| DOD | Damage Description | EXP | LB | UB |
| --- | --- | --- | --- | --- |
| 1 | Threshold of visible damage | 63 | 53 | 80 |
| 2 | Loss of roof covering material (<20%), gutters and/or awning; loss of vinyl or metal siding  | 79 | 63 | 97 |
| 3 | Broken glass in doors and windows  | 96 | 79 | 114 |
| 4 | Uplift of roof deck and loss of significant roof covering material (>20%); collapse of chimney; garage doors collapse inward or outward; failure of porch or carport  | 97 | 81 | 116 |
| 5 | Entire house shifts off foundation  | 121 | 103 | 141 |
| 6 | Large sections of roof structure removed; most walls remain standing  | 122 | 104 | 142 |
| 7 | exterior walls collapsed  | 132 | 113 | 153 |
| 8 | Most walls collapsed except small interior rooms. | 152 | 127 | 178 |
| 9 | All walls collapsed | 170 | 142 | 198 |
| 10 | Destruction of engineered and/or well constructed residence; slab swept clean | 200 | 162 | 220 |

- Example DODs for a Framed House DI  (FR12 or DI2)

- Note some consecutive DODs have larger overlap than others

- Objectives:  2,  methodology; 3, EF-Scale structure

**Notes:**
In the graphical form, 
you can see some adjacent DODs with similar wind speed estimates,
Such as those between DODs 3 and 4. 
Note how much overlap there is between DODs in general.  
The uncertainty regarding building design and exposure should be reflected, as it is here, in the design of this kind of scale.  

This is an example from 1-2 family residences.

## Relating the F-scale with the EF-Scale

- Need of historical continuity
- 2nd set of experts assigned F-scale ratings to the same damage descriptions
- Median F-scale wind speeds compared to that of expected EF-Scale wind speeds

- Objectives:  2,  methodology; 4, EF vs F-Scale

**The F-Scale wind speed was converted from the fastest 1⁄4 mi to a 3 sec gust.**

- Bill Bunting – NWSFO – Fort Worth, Texas
- Brian Peters – NWSFO – Calera, Alabama
- John Ogren – NWSFO – Indianapolis, Indiana
- Dennis Hull – NWSFO – Pendleton, Oregon
- Tom Matheson – NWSFO – Wilmington, North Carolina
- Brian Smith – NWSFO – Valley, Nebraska

- F5 to EF5 threshold wind speed

**Notes:**
Remember that the EF-Scale forum, and we also, want to maintain some type of the integrity and continuity between the old F-Scale and the new EF-Scale.  Otherwise, we fear a significant break in the climatology may result.  One way to help resolve this is to see how well the EF and F-Scale match up when damage is being assessed by a surveyor.  

One way the Steering Committee decided to match the scales was to have a second set of damage survey experts estimate a similar set of pictures as what the EF-Scale expert team saw, but in this case, rate them by the F-scale.  The second set of experts consisted of WCMs and other experienced damage survey experts that participated in the Quick Response Teams from 2003 to 2006.  Median wind speeds were derived from the F-scale ratings and then compared to the expected wind speed of the EF-Scale.

You may find that the median wind speed in the F-scale represented here is a little different.   That is because they were converted from the fastest 1⁄4 mi wind of the F-scale to the 3 second gust frame of reference in the EF-Scale.  This analysis serves the function that the old database can be converted to the EF-Scale, or at least the two databases can be reconciled.

Note that the F5 ratings match closely to the EF5 winds, and the same is true for the lower ratings for both scales.  Given the good correlation in this curve, there is high confidence that this relation is good.   Now we can use the regression equation to establish the wind speed criteria for the EF-Scale ratings.

By the way, this strategy does not eliminate all artifacts that could occur in the climatology by switching to the EF-Scale.  There are some differences in the DODs that can result in you deriving a different rating between the two scales.  I don’t expect that you would come up with a difference greater than one rating. But it is possible in some cases.  We don’t know about how these differences will impact the climatology.

## F-Scale Converted to EF-Scale 

| F Scale | Wind Speed | EF-Scale | Wind Speed |
| --- | --- | --- | --- |
| F0 | 45-78 | EF0 | 65-85 |
| F1 | 79-117 | EF1 | 86-109 |
| F2 | 118-161 | EF2 | 110-137 |
| F3 | 162-209 | EF3 | 138-167 |
| F4 | 210-261 | EF4 | 168-199 |
| F5 | 262-317 | EF5 | 200-234 |

- Wind speeds in mph, 3-second gust

- Objectives:  3, EF-Scale structure; 4, EF vs F-Scale

**Notes:**
McDonald and Mehta took the regression and applied it to convert the F-scale rating wind speed ranges to the EF-Scale.  In this way, there should be continuity in the way we rate the damage.  Again, note that the F-scale wind speed ranges you see here are converted from the fastest 1⁄4 mile to a 3 second gust.  As a result they are a bit higher than what you may see elsewhere.  The 3 second gust is thought to represent how the wind damages structures a little better than the fastest 1⁄4 mile wind speed.  

## DOD to Wind Speed to EF-Scale

| EF-Scale Categories | Wind Speed Ranges |
| --- | --- |
| EF0 | 65-85 |
| EF1 |   86-110 |
| EF2 | 111-135 |
| EF3 | 136-165 |
| EF4 | 166-200 |
| EF5 | >200 |

- Objectives: 3, EF-Scale structure

- Wind speeds in mph, 3-second gust

**Notes:**
The final step in establishing the EF-Scale rating wind speed bounds is to round them off.  From estimating the wind speed from the DOD of any DI, you can make the bridge to establishing an EF-Scale rating using this table.

## Comparing Beaufort, F, and Mach Scales

- 1

- 2

- 3

- 4

- 5

- 6

- 7

- 8

- 9

- 10

- 11

- 12

- 0

- Beaufort Scale

- 1

- 2

- 3

- 4

- 5

- 6

- 7

- 8

- 9

- 0

- 10

- 11

- 12

- Fujita Scale

- 0.6

- 1.0

- Mach Scale

- B1

- B3

- B5

- B7

- B9

- B11

- F0

- F1

- F2

- F3

- F4

- F5

- F12

- M1.0

- M0.6

- M0.7

- M0.8

- B17

- Beaufort:      V = 1.870B3/2		mph
- F – scale:     V = 14.1(F+2)3/2	mph
- Mach scale:  V = (742 +1.3)M	mph

- These scales have wind speed defined first, impacts/damage were assigned to wind speeds.

- Objectives:  3, EF-Scale structure; 4, EF vs F-Scale

**Notes:**
Let us show you how the EF-Scale rating wind speeds compares to that of the three most famous wind speed ratings.  First, let’s graphically review the three wind speed scales.
This is a variation of a graphic created by Ted Fujita to show how and why the F-scale was created.  Just like the Beaufort
and Mach scales, 
the F-scale is a wind speed scale intended to bridge the gap between the other two scales. 

Thus, all three scales have a function describing the winds.  Fujita attempted to fit the observed damage to the scale and he decided that a solid house wiped clean off its foundation would be an F5.  That automatically fixed the wind speed to the F-scale, and now many years of historical inertia have roughly kept Fujita’s original damage descriptions firmly attached to the wind speeds through the various F-ratings.

## Comparing F and EF-Scales

**Comparing F and EF-Scales**

- 1

- 2

- 3

- 4

- 5

- 6

- 7

- 8

- 9

- 10

- 11

- 12

- 0

- Beaufort Scale

- 1

- 2

- 3

- 4

- 5

- 6

- 7

- 8

- 9

- 0

- 10

- 11

- 12

- Fujita Scale

- 0.6

- 1.0

- Mach Scale

- B1

- B3

- B5

- B7

- B9

- B11

- F0

- F1

- F2

- F3

- F4

- F5

- F12

- M1.0

- M0.6

- M0.7

- M0.8

- B17

- EF0

- EF1

- EF2

- EF3

- EF4

- EF5

- EF-Scale

- The EF-Scale is a damage scale:  speeds were estimated from the damage

- Objectives:  3, EF-Scale structure; 4, EF vs F-Scale

**Notes:**
We overlay the wind speed ranges of the EF-Scale on the other scales.  

The EF-Scale is different because the damage scale was created first and reasonable wind speeds later attached to the EF ratings.  

There is no function relating EF rating to wind speed.  If we were to keep the old F-scale but update it using the new wind speeds, there would be no more F5’s, and much fewer F4’s than today.  With regards to the frequency of various F-scale tornadoes, there would be a large climatological break.  The EF-Scale design allows us to avoid making such an obvious fracture in the climatology but the cost is losing a convenient determination of wind speed as a function of rating.

Remember, the old F-scale still serves the function as a wind speed scale to bridge the gap between the Beaufort and Mach scales.  If we were to be true to the F-scale, and that indeed the estimated winds to cause the damage described in the EF-Scale are true, then no observed historical damage could be assigned an F-5.  

## DOD to Wind Speed to EF-Scale question

| DOD | Damage Description – Framed House | EXP | LB | UB |
| --- | --- | --- | --- | --- |
| 1 | Threshold of visible damage | 63 | 53 | 80 |
| 2 | Loss of roof covering material (<20%), gutters and/or awning; loss of vinyl or metal siding  | 79 | 63 | 97 |
| 3 | Broken glass in doors and windows  | 96 | 79 | 114 |
| 4 | Uplift of roof deck and loss of significant roof covering material (>20%); collapse of chimney; garage doors collapse inward or outward; failure of porch or carport  | 97 | 81 | 116 |
| 5 | Entire house shifts off foundation  | 121 | 103 | 141 |
| 6 | Large sections of roof structure removed; most walls remain standing  | 122 | 104 | 142 |
| 7 | exterior walls collapsed  | 132 | 113 | 153 |
| 8 | Most walls collapsed except small interior rooms. | 152 | 127 | 178 |
| 9 | All walls collapsed | 170 | 142 | 198 |
| 10 | Destruction of engineered and/or well constructed residence; slab swept clean | 200 | 162 | 220 |

- Objectives:  3, EF-Scale structure

- Quiz:  What DOD best corresponds with this damage?

**Notes:**
Let’s try an example.  I give you a picture of a one story house, stucco exterior, load path meeting codes.  What do you think the damage rating is for this house?  Up next will pop a quiz responder where you can make the call.  I pause this slide so that you may view the damage descriptions and make a decision before you go on.

## EF-Scale_L1_1

**Notes:**
If you see the choices extend below the bottom of the page, use the scroll bar on the right side of the quiz page to view all choices.  The submit button is at the bottom of all the choices.  You have two chances to correctly answer the quiz item.  Don't worry, you're not being graded.  :^)  When you're finished with the quiz and you want to go on with the lesson, select the 'finish' button, or you may leave the quiz at any time.

## DOD to Wind Speed to EF-Scale review

| DOD | Damage Description – Framed House | EXP | LB | UB |
| --- | --- | --- | --- | --- |
| 1 | Threshold of visible damage | 63 | 53 | 80 |
| 2 | Loss of roof covering material (<20%), gutters and/or awning; loss of vinyl or metal siding  | 79 | 63 | 97 |
| 3 | Broken glass in doors and windows  | 96 | 79 | 114 |
| 4 | Uplift of roof deck and loss of significant roof covering material (>20%); collapse of chimney; garage doors collapse inward or outward; failure of porch or carport  | 97 | 81 | 116 |
| 5 | Entire house shifts off foundation  | 121 | 103 | 141 |
| 6 | Large sections of roof structure removed; most walls remain standing  | 122 | 104 | 142 |
| 7 | exterior walls collapsed  | 132 | 113 | 153 |
| 8 | Most walls collapsed except small interior rooms. | 152 | 127 | 178 |
| 9 | All walls collapsed | 170 | 142 | 198 |
| 10 | Destruction of engineered and/or well constructed residence; slab swept clean | 200 | 162 | 220 |

- Objectives:  3, EF-Scale structure

- Expected wind 97 mph

**Notes:**
This house suffered an uplift of the roof deck, certainly >20% roof loss.  There’s a garage door-like opening that’s been covered in plywood.  I suspect that and possibly a car port was damaged or removed by the wind.  This description fits best with DOD4 and an estimated wind speed range from 81 – 116 mph.  I gave it the EXP wind of 97 mph.  Let’s go to the next page to apply an EF#  rating.

Determining whether or not you should stick with an expected wind speed requires a lot of experience and knowledge of construction quality and exposure.  The next lesson dives into a little more detail on construction quality about at least one type of DI:  the one- and two-family house.

## EF-Scale answer

| EF-Scale Categories | Wind Speed Ranges |
| --- | --- |
| EF0 | 65-85 |
| EF1 |   86-110 |
| EF2 | 111-135 |
| EF3 | 136-165 |
| EF4 | 166-200 |
| EF5 | >200 |

- Wind Speed in mph, 3-Second gust

- Objectives:  3, EF-Scale structure

**Notes:**
An EF1 covers the winds we estimated from the picture.  Note that if we determined that this structure had a sound roof (hurricane) clip installation, perhaps I might’ve given an UB wind for DOD4 and then that would bump it to EF2.  Not knowing that, I will remain here at EF1.

## Strengths of EF-Scale

- EF-Scale
- 28 DIs
- Accounts for differences of structural integrity within a DI
- Wind speeds determined from damage
- Continuity from the F-scale
- Expandibility, Flexibility, Extensibility

- F Scale
- Only a Couple DIs
- No accounting for differences of structural integrity within a DI
- Wind speeds not derived from damage

- Objectives:  5, EF-Scale strengths

**Notes:**
The EF-Scale is more comprehensive than the F-scale with 28 DIs.  It accounts for structural diversity in strength within DIs and its effects on assigning wind speeds to DODs. Wind speeds are determined from damage using expert elicitation methods.  There is  continuity from the legacy to the new scale.  And the EF-Scale is expandible, meaning new DIs can be added, combined and estimated wind speeds assigned to the DODs can be modified.

## EF-Scale limitations

- Change in scale may introduce artifacts into the historical record
- Complicated
- Wind speeds subject to change for each rating
- No function relating wind speed to rating
- Debate continues about wind speed assignments

- Objectives:  6, EF-Scale limitations

**Notes:**
The EF-Scale isn’t perfect.  There still could be artifacts introduced into rating structures that could yield difficult to measure changes in tornado intensity climatology.  The EF-Scale requires a steep learning curve beyond the capabilities of these modules.  You’ll need to gain experience in using it given a host of resources (we’ll let you know what these are), and by communicating with experts and your peers.  Wind speeds are subject to change which may invoke a challenge in public education when these changes occur.  As opposed to the F-scale, there is no elegant wind speed vs rating function that helps bridge the gap between the Beaufort and Mach scales.  Finally, there is still debate going on with regards to wind speed assignments.   

## EF-scale_L1-2

**Notes:**
If you see the choices extend below the bottom of the page, use the scroll bar on the right side of the quiz page to view all choices.  The submit button is at the bottom of all the choices.  You have two chances to correctly answer the quiz item.  Don't worry, you're not being graded.  :^)  When you're finished with the quiz and you want to go on with the lesson, select the 'finish' button, or you may leave the quiz at any time.

## Summary:  Lesson 1

- EF-Scale created to provide more DIs, more realistic wind speeds
- EF-Scale winds were estimated using expert elicitation
- EF-Scale contains 28 DIs, each with several DODs ranging from first damage to destruction or if the estimated wind speeds correspond to an EF 5 rating.
- EF-Scale winds significantly lower than F-scale for EF (F3) and higher
- EF-Scale is complicated requiring a longer time for familiarization

- Objectives:  1-6

**Notes:**
EF-Scale created to provide more DIs, more realistic wind speeds
EF-Scale winds were estimated using expert elicitation
EF-Scale contains 28 DIs, each with several DODs ranging from first damage to destruction or if the estimated wind speeds correspond to an EF 5 rating.
EF-Scale winds significantly lower than F-scale for EF (F3) and higher
EF-Scale is complicated requiring a longer time for familiarization

## References and suggested reading

- McDonald, J.R. and K.C. Mehta, 2001: Summary report of the Fujita Scale forum. Wind Science and Engineering, Texas Tech University, Lubbock, TX, 36 pp.
- Phan, L.T. and E. Simiu, 1998: The Fujita tornado intensity scale: a critique based on observations of the Jarrell tornado of May 27, 1997. NIST Tech. Note 1426, U.S.  Department of Commerce, Gaithersburg, MD, 20 pp.
- SSHAC, 1997: Recommendations for probabilistic seismic hazard analysis: guidelines on uncertainty and use of experts, NUREG/CR6372, UCRL-ID-122160, Vol. I, Lawrence Livermore National Laboratory, Livermore, CA, 131 pp.

- Suggested reading:
- A Recommendation for the Enhanced Fujita Scale:  _[http://](http://www.spc.noaa.gov/efscale/)__[www.spc.noaa.gov/efscale](http://www.spc.noaa.gov/efscale/)__[/](http://www.spc.noaa.gov/efscale/)_

**Notes:**
Take a look at these references if you like.  A full report of the EF-Scale is available on the Storm Prediction Center web site or using the link above.  This document has all the tables of DODs for each of the 28 DIs.  

## In Lesson 2

- Lesson 2 provides you a chance to use the EF-Scale on some damage tracks

**Notes:**
In lesson 2, you will apply the EF-Scale to some case studies.  This way, you’ll get a better feel for how the EF-Scale should be applied in a damage survey.  You’ll also be introduced to the EF-kit.  It is an application that helps you in a survey or to get familiar with the EF-Scale.

## Contacts

- If you have any questions about this lesson, contact
- Jim LaDue,  _[James.G.LaDue@noaa.gov](mailto:James.G.LaDue@noaa.gov)_
- Dan McCarthy, Daniel.McCarthy@noaa.gov

**Notes:**
Contact Jim LaDue or Dan McCarthy with the addresses above.