Downscaling for Fire Weather –
Forecasting in Complex Topography
Heath Hockenberry
National Weather Service Fire Weather Program Manager

Fire Weather – How are forecasts made?
Like everything else, start with the broad model output.
Unlike everything else, apply basic conceptual knowledge of terrain and fuels.
So how do we get from this….
To this ?

Fire Weather – “Old School” Meteorology
Operational Fire weather is far from a complex, fine scale model with fire feedbacks and parameterizations.
Conceptual models are still the basis of forecasting in complex terrain.
Essential reading Essential Training

Basic Concepts and Terminology of
Wildland Fire

Introduction to Fire Behavior Terms
This example…Spotting
Fire producing sparks or embers that are carried by the wind or convection that start new fires beyond the main fire

The “heart” of fire weather is taught in this course…
Stability Winds

Adjustment to Temperature using Average Lapse Rate
Known: Elevations and the temperature at the lowest elevation
Elevation Change: 2000 feet
Average Lapse Rate -3.5F/1000 feet
Simple calculations like this are done all the time in fire weather, for temperature adjustments.

The thermal belt Inversion Depth

Advanced Wildland Fire Behavior
Wind Downscaling…
• General
Winds
• Local
Winds

Examples of Local Wind circulations: slope winds and sea breezes

20 FT WINDS RELATIONSHIP
20 ft winds = General Winds + Local Winds
Which dominates?
General? Local? Both?

Terrain Forced Flows
The effects of terrain on General Winds:
Dissipation of wind by terrain features
Acceleration of wind by terrain features
Diversion of wind around terrain features
Due to the complexity of terrain and atmospheric interaction these are…
DIFFICULT TO PREDICT!

Terrain Correction Factors
Suggested General Wind correction factors:
Assuming:

Gently sloped terrain.

Neutral or unstable (or above inversion).

Windward slope exposed to general winds.
Upper 1/3 of slope: 0.4 to 0.6 of General Wind
Middle 1/3 of slope: 0.3 to 0.4 of General Wind
Lower 1/3 of slope: 0.2 to 0.3 of General Wind
Sheltered Areas: near zero

Terrain Correction Factors
Example
0-1 mph
6 mph
6 mph
6 mph
Local slope winds

Terrain Correction Factors Example
20 mph
0-1 mph
5 mph
7 mph
10 mph
General Winds

Terrain Correction Factors Example
20 mph
2 mph
16 mph
11 mph
13 mph
20 ft Winds=
General Winds + Local Winds

Terrain Correction Factors
Example
20 mph
0 mph
2 mph
2 mph
16 mph
20 ft Winds=
General Winds + Local Winds

High Elevation Gaps
Strong pass winds can also result from upper winds combined with a low level pressure gradient.

Forecasting on an Incident Management Team…

Satellite Dish allows ingest and dissemination of forecast products

Why Pibals?
Diurnal Wind Patterns.
Complex Terrain.
Smoke/Public Health Concerns
Model problems!!!!

Incident Management Team
Worried about the forecasted Gap wind Event
↑ East
East Flank of Fire
Left Alone →
↓ West
South →
July 7 th 2003 Brent Wachter

Protect Taos Pueblo and Taos to the West
← Air Tanker Drop

Data: Rick Stratton, SEM, Missoula Fire Lab

Sanford Fire
Fuel

WTR Weather Stream File for FARSITE
ENGLISH
8 12 0 600 1700 54 87 50 20 7500
8 13 0 600 1700 52 88 50 20 7500
8 14 0 600 1700 52 88 50 25 7500
8 15 0 600 1700 57 87 50 27 7500
8 16 0 600 1700 56 81 50 23 7500
8 17 0 600 1700 57 81 50 20 7500
8 18 0 600 1700 53 81 50 21 7500

Regression Equations Techniques
National Fire Danger Rating
Forecasts from local NWS
Offices.
Multiple Regression for Grassy Mtn RAWS -
Summer Min Eq y=(.34A)+(0.037B)+(-0.0021C)+(0.62D)+2.3
R2=0.86
80
60
40
20
0
0 20 40
Boise Min Temp
60 80
Grassy fcst
Fire-business driven fuel dryness prediction, tailoring broad scale models to predict fuels’ receptiveness to fire.

DGEX vs. GFS (Model Downscaling) http://wwwt.emc.ncep.noaa.gov/mmb/mmbpll/dgexhome.ops/
500 mb ht/Vort
850 mb wind

NWS Mets and IMETs Chuck Redman, Coleen
Decker, Chris Gibson, Brent Wachter, Jim
Prange, Bob Servick, Julia Rutherford, Bernard
Meier, Larry VanBussum, and Chuck Baker.
Predictive Services GACC Mets Terry Marsha,
John Saltenberger and Tim Mathewson.
NCEP’s Geoff DiMego.
The National Interagency Fire Center Training
Branch.