1. A Mountain Wind Model for Assisting Fire Management
Gary L. Achtemeier
Center for Forest Disturbance Science
USDA Forest Service, Athens, GA

2. Purpose for Study
Forestry organizations responsible for managing prescribed fire or controlling wildfire rely on weather forecasts of wind speed and wind direction for planning and allocation of resources.

3. Purpose for Study
At the locations of fire sites in mountainous areas, winds are highly variable and may differ from winds at distant weather stations or from winds collected at safe sites just a few kilometers from fire lines.

4. Purpose for Study
These uncertainties in winds can upset plans and place fire fighters in jeopardy.

5. Background for Study
Weise, et al., (2007) comparison study of several wind schemes and impacts on FARSITE predictions of fire spread for the Esperanza fire in southern California.
Need winds in complex terrain to link with fire spread and relative emissions model, Rabbit Rules.
Something fast and easy.

6. Rule-Driven Solutions
Complex physical equations recast as simple equations written as computer programs solved recursively (Wolfram, 2002).
Success with the fire spread model Rabbit Rules.
Add rules as needed.

7. MWM – Rule M1
The movement of air through mountainous terrain can be explained by a simple pressure function.

8. MWM – Rule M1 Mathematical Form of the P-Function

9. MWM – Rule M1
Inserted into the pressure gradient terms in a simple CFD wind model that predicts average winds for a 100 m deep layer draped over terrain.
Results

10. Stone Mountain, GA Solitary granite monolith
Rises 235 m above surrounding terrain
1200 m by 960 m

11. 1 2 3 4
Askervein Hill

15. Part of a 400 m high ridge near Ashwood, VA
Part of a 400 m high ridge near Ashwood, VA. (Image courtesy Google Earth)

16. 1

17. 2 1

18. 3 2 1

19. 4 3 2 1

20. 5 4 3 2 1

22. Map of MWM winds at 0900 PDT 26 October 2006.

23. Conclusions
The Mountain Wind Model is a work in progress. Rule M1 produces wind fields as shown. Additional rules would be required to model mountain winds for the following conditions:
Turbulent flows under high winds,
Flows at higher terrain where pressure observations currently used lose validity,
Light winds dominated by thermally-induced circulations – both day and night,
Stable temperature strata, and
Probably more.

24. MWM - Is it realistic? Reinventing the wheel? ????