# Presentation: 335027

## A Detailed Look at Extreme Wind Damage in Derecho Events 

- NWS/Weather Forecast Office, Norman OK
- Robert H. Johns
- NWS/Storm Prediction Center, Norman OK

**A Detailed Look at Extreme Wind Damage in Derecho Events**** **

## Extreme Non-Tornadic Wind Damage Events 

**XDW**** – **e_**X**_treme** **_**D**_amaging** **_**W**_ind

## Extreme Non-Tornadic Wind Damage Events 

- Pakwash Forest Blowdown Event
- 18 July 1991 - Northwest Ontario Canada

## What is a Derecho?

- Used national radar summary charts to cross-check reports and observations for temporal and spatial continuity of the event

**From Johns and Hirt, 1987**

- Area of widespread convectively induced wind damage and/or severe wind gusts produced by the same MCS that meet specified criteria for length, chronological progression, and temporal continuity

## What is a Derecho?

## Radar Criteria

**From Johns and Hirt 1987**

- The derecho producing MCS must have temporal and spatial continuity. However, movement of associated radar echoes need *NOT* be continuous
- 2) Multiple swaths of wind damage (gusts) MUST be a part of the same MCS (from radar summary charts)

## What JH87 Did NOT Do

## A Derecho is an EVENT

**A Derecho is an **_***EVENT***_

## What Convective Elements Are Associated with XDW Events?

- Some Events Involve Supercells

- Supercell

**1 July 1997 – Central Minnesota**
**29 June 1998 – Central Iowa**
**4 July 1999 – Northern Minnesota**
**27 May 2001 - Oklahoma**

- Non-Supercell

**15 July 1995 – Upstate New York**
**30-31 May 1998 – Minnesota to New York**

## 1 July 1997 – Central Minnesota

## 1 July 1997 – Central Minnesota

## 1 July 1997 – Central Minnesota

**Range ~ 48 km (24 nm)**

**1 kft**

**4 kft**

**7 kft**

**9 kft**

**12 kft**

**16 kft**

**22 kft**

**26 kft**

## 29 June 1998 – Central Iowa

## 29 June 1998 – Central Iowa

## 29 June 1998 – Central Iowa

**1 kft**

**4 kft**

**10 kft**

**19 kft**

**Range ~ 35 km (17 nm)**

## 4 July 1999 – Northern Minnesota

## 4 July 1999 – Northern Minnesota

## 4 July 1999 – Northern Minnesota

**7 kft**

**17 kft**

**24 kft**

**31 kft**

**Range ~ 140 km (71 nm)**

## 4 July 1999 Blowdown

## 4 July 1999 – Northern Minnesota

**BWCA Forest Blowdown Event**

## 4 July 1999 Damage

## 4 July 1999 Blowdown

## 4 July 1999 Blowdown

**0.5****0**
**Reflectivity**

**VIL**

**0.5****0**
**Velocity**

**0.5****0**
**SR Velocity**

**Range ~ 210 km (100 nm)  Beam Height 9.5 kft**

## May 27, 2001 KS-OK-TXMemorial Day Derecho

**Severe Reports 27 May 2001**

**1 Death**

**4 Injuries**

**160,000 without power**

**Over $300 million damage**

## The “Environment”

**OUN**
**00Z 28 May 2001**

**CAPE   4874 j/kg**

**CIN   0 j/kg**

**LI   -11**

**WBZ   11653 ft**

**700-500 LR   7.6 deg/km**

**LCL   858 mb**

## The “Environment”

**OUN**
**00Z 28 May 2001**

**Sfc-6km shear   30 m/s**

**Sfc-3km SRH   264m****2****/s****2**

**BRN   47**
**BRN Shear 67 m****2****/s****2**

**LFC-EL wind   280/30kt**

**Storm motion   320/40kt**

## Oklahoma Mesonet Peak Winds

## Visual Appearance

*****

**Photo taken here **
**at 723 pm CDT**

**KTLX Reflectivity 0025 UTC**

## 27 May 2001– Oklahoma

## 27 May 2001– Oklahoma

## 27 May 2001– Oklahoma

## 27 May 2001– Oklahoma

## 27 May 2001– Oklahoma

## Non-Supercell XDW Events

**15 July 1995 - Upstate New York**

## Non-Supercell XDW Events

**15 July 1995 - Upstate New York**

## Non-Supercell XDW Events 

**30-31 May 1998 - Minnesota to New York **

## Non-Supercell XDW Events 

**30-31 May 1998**

**Spencer SD Tornadic Supercell**

**Deaths:      6**
**Injuries:   150**
**Damage:  ~ $20,000,000**

## Non-Supercell XDW Events 

**30-31 May 1998 – MSP metro area**

## Non-Supercell XDW Events 

**30-31 May 1998 –southern Wisconsin**

## Non-Supercell XDW Events 

**30-31 May 1998 – southern Wisconsin**

**5 kft**

**12 kft**

**24 kft**

**18 kft**

## Operational Considerations

-  Supercells *within* a derecho producing
-    MCS can be associated with an enhanced
-    threat for XDW

-  Supercell XDW events *may* have somewhat
-    different characteristics than Bow Echo
-    XDW events

-  In *some* derecho events - the most extreme
-    damage is associated with supercells

## Unique? Characteristics of Supercell XDW Events

**Quite ****long in duration**** at any one location along the path (10-20 minutes - or longer in extreme cases vs. a few minutes or less for bow echoes)**
**Have a much higher probability of being accompanied by ****large hail**** (> 4cm)**
**3) Very ****tight damage gradients**** along the periphery of XDW area**

## Operational Considerations

**Overall message is that warning forecasters need to be keenly aware of an enhanced potential for wind damage (possibly high-end) when circulations are present**

- Most likely area for XDW is near the low-level mesocyclone and in the precip-filled RFD area

- Much more than a simple ‘downburst’

## Acknowledgements

-  NWS Warning Decision Training Branch (Formerly OSF/OTB)
**David Andra** - NWSFO, Norman OK
**Todd Krause** - NWSFO, Minneapolis MN
**Karl Jungbluth** – NWSFO, Des Moines IA
**Ken LaPenta** – NWSFO, Albany NY
**Rusty Kapela** – NWSFO Milwaukee WI
**Charles Doswell III** – National Severe Storms Laboratory
**Les Lemon** – Consulting Meteorologist
**Jeff McKay** – Owatonna MN

**Acknowledgements**

## On the Internet

**Point your browser to:**
- _www.srh.noaa.gov/oun/papers/derecho.html_