# Presentation: 929015

## Using Short Range Ensemble Model Data in National Fire Weather Outlooks

- Sarah J. Taylor
- David Bright, Greg Carbin, Phillip Bothwell
- NWS/Storm Prediction Center
- Richard Naden
- Southwest Predictive Services

## Overview

- SPC Fire Weather Program
- Use of short range ensemble forecasts (SREF)
- Case Studies
- July 8, 2003
- Recent Santa Ana event (October 25-31, 2003)
- Conclusions

## SPC Fire Weather Program

- Fire weather forecasts began in 1998
- Purpose is to provide national fire weather guidance to NWS, federal, state and local government agencies
- Product will outlook areas where critical fire weather conditions combined with pre-existing fuel conditions forecast to occur

## Critical Fire Weather Areas
Extremely Critical Fire Weather Areas
Dry Thunderstorm Areas
Issued for widespread dry lightning

- Extremely Critical Fire Weather Areas
- Dry Thunderstorm Areas
- Issued for widespread dry lightning

- SPC Fire Weather ProgramTypes of Outlooks:

## Critical Fire Weather Area

- Outlooks based on forecasts of Relative Humidity, maximum temperatures, sustained winds, and pre-existing fuels
- RH criteria varies by geography
- Temperatures must be greater than 60 F
- Sustained surface winds (10 meter) must be greater than 20 mph
- High Fire Danger Class Index, low 100/1000 hr fuel moisture, long term drought

## SPC Fire Weather Outlook Issued on Sunday October 26, 2003

## Use of SREF output

- What is an ensemble forecast??
- Collection of different model solutions
- By changing the initial conditions, different forecast solutions are created
- SPC uses a 15 member ensemble from NCEP
- Consists of Eta, Eta KF, RSM models
- 48 km resolution

## Use of SREF output

- Ensemble forecasts first applied operationally in the 1990s
- Studies have shown that ensembles are more skillful than using 1 single model (Wandishin et al, 2001, Bright and Mullen 2001)
- SPC began using SREF operationally in 2002

## Use of SREF output

- At the SPC, nearly 300 SREF products are available:
- Relative Humidity
- Temperature
- Wind
- Fosberg Fire Weather Index
- Haines Index
- Convective precipitation
- Combinations of the above

## Use of SREF outputStatistical Fields

- Mean and Spread
- Shows the “average” of the ensemble
- Will smooth small scale features
- Probability
- Indicate the percentage of ensemble members which meet certain criteria
- Extreme values
- Useful in predicting “worst case” events

## Fosberg Fire Weather Index Mean and Standard Deviation Valid July 8 at 2100 UTC

## Probability of Fosberg FWI greater than 75

- Probability of Fosberg FWI greater than 50

## Maximum Fosberg Fire Weather Index valid 18 UTC July 8, 2003

## Case Studies/Verification

- SPC Fosberg Fire Weather Index is used to verify fire weather outlooks
- Index is calculated with local objective analysis scheme
- Fosberg FWI greater than 50 is a “threshold” value

## Case Studies (July 8, 2003)

- Forecast valid at 18 UTC on July 8
- Minimum RH with Mean Surface Wind

- Sustained winds 20 kts or greater
- Minimum RH less than 5%

## Maximum Fosberg Fire Weather Index valid 18 UTC

- Observed maximum Fosberg FWI - valid 2100 UTC July 8, 2003

## Santa Ana Event October 2003

- Statewide loss of 20 lives
- 2600 houses with over 725,000 acres burned
- Monetary loss figures for the disaster are estimated to be over two billion dollars

## Satellite Loop

## Image courtesy of Liam Gumley, Space Science and Engineering Center, UW-Madison

**2055 UTC October 27, 2003**

## Slide 21

## Loop runs from 18 UTC October 26- 00 UTC October 27

## Loop runs from 18 UTC October 26- 00 UTC October 27

## Loop runs from 18 UTC October 26- 00 UTC October 27

## Santa Ana Event October 2003

- SREF showed some skill
- Increased resolution of model would likely create better forecasts
- Fosberg Fire Weather Index did not verify well for this event

## Conclusions

- Short range ensemble forecasts will be used more and more in the future
- With increased experience and development, ensembles will likely prove to be more useful than a single deterministic model

## Conclusions (Continued)

- Model resolution increases
- Better model physics
- Ongoing research in Initial Condition perturbations
- Increased ensemble spread
- Data mining tools and display

## Acknowledgements

- The authors would like to thank Steve Weiss at the Storm Prediction Center for his review and Jason Levit for his assistance with case study data

## For more information

- Visit the SPC Fire Weather Page:
- _[www.spc.noaa.gov/fire](http://www.spc.noaa.gov/fire)_
- Page contains latest SPC fire outlooks, Eta forecasts and latest surface analysis
- Will include ensemble forecast guidance in the future
- This presentation is available online:
- 	www.spc.noaa.gov/publications/taylor/srefams.html
- Email: Sarah.Taylor@noaa.gov