Downscaling for Fire Weather – Forecasting in Complex Topography

Heath HockenberryNational Weather Service Fire Weather Program Manager

Fire Weather – How are forecasts made?Fire Weather – How are forecasts made?

Like everything else, start with the broad model output.Like everything else, start with the broad model output.

Unlike everything else, apply basic conceptual Unlike everything else, apply basic conceptual knowledge of terrain and fuels.knowledge of terrain and fuels.

So how do we get from this….So how do we get from this…. To this ?To this ?

Fire Weather – “Old School” MeteorologyFire Weather – “Old School” Meteorology

Operational Fire weather is far from a complex, fine Operational Fire weather is far from a complex, fine scale model with fire feedbacks and parameterizations.scale model with fire feedbacks and parameterizations.Conceptual models are still the basis of forecasting in Conceptual models are still the basis of forecasting in complex terrain.complex terrain.

Essential readingEssential reading Essential TrainingEssential Training

S-190 Introduction to S-190 Introduction to Wildland Fire BehaviorWildland Fire Behavior

Basic Concepts and Terminology of Basic Concepts and Terminology of Wildland FireWildland Fire

Introduction to Fire Behavior TermsIntroduction to Fire Behavior TermsThis example…SpottingThis example…Spotting

Fire producing sparks or embers that are carried by Fire producing sparks or embers that are carried by the wind or convection that start new fires beyond the wind or convection that start new fires beyond the main firethe main fire

S-290 Introduction to S-290 Introduction to Wildland Fire BehaviorWildland Fire Behavior The “heart” of fire weather is taught in The “heart” of fire weather is taught in

this course…this course…StabilityStability WindsWinds

Adjustment to Temperature using Average Lapse Rate

S-290 TechniquesS-290 Techniques

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 beltThe thermal belt Inversion DepthInversion Depth

S-290 TechniquesS-290 Techniques

S-390 and S-490 S-390 and S-490 Advanced Wildland Fire BehaviorAdvanced Wildland Fire Behavior

Wind Downscaling…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 Due to the complexity of terrain and atmospheric interaction these are…atmospheric interaction these are…

DIFFICULT TO PREDICT!DIFFICULT TO PREDICT!

Terrain Correction Factors

Suggested General Wind correction factors:Suggested General Wind correction factors:

Assuming:Assuming: Gently sloped terrain.Gently sloped terrain. Neutral or unstable (or above inversion).Neutral or unstable (or above inversion). Windward slope exposed to general winds.Windward slope exposed to general winds.

Upper 1/3 of slope: 0.4 to 0.6 of General WindUpper 1/3 of slope: 0.4 to 0.6 of General Wind

Middle 1/3 of slope: 0.3 to 0.4 of General WindMiddle 1/3 of slope: 0.3 to 0.4 of General Wind

Lower 1/3 of slope: 0.2 to 0.3 of General WindLower 1/3 of slope: 0.2 to 0.3 of General Wind

Sheltered Areas: near zeroSheltered Areas: near zero

Terrain Correction Factors Example

0-1 mph6 mph

6 mph6 mph

Local slope windsLocal slope winds

Terrain Correction Factors Example

0-1 mph5 mph

7 mph10 mph

General WindsGeneral Winds

20 mph

Terrain Correction Factors Example

2 mph11 mph

13 mph16 mph

20 ft Winds=20 ft Winds=General Winds + Local WindsGeneral Winds + Local Winds

20 mph

Terrain Correction Factors Example

20 ft Winds=20 ft Winds=General Winds + Local WindsGeneral Winds + Local Winds

0 mph2 mph

2 mph16 mph

20 mph

High Elevation Gaps

Strong pass winds can also result from upperwinds combined with a low level pressure gradient.

Advanced Incident Advanced Incident Meteorology ForecastingMeteorology ForecastingForecasting on an Incident Management Team…Forecasting on an Incident Management Team…

Satellite Dish allows ingest and dissemination of forecast products

IMET ForecastingIMET Forecasting

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

July 7th 2003 Brent Wachter

Incident Management Team Worried about the forecasted Gap wind Event

East Flank of Fire Left Alone →

↑ East

South →

↓ West

← Air Tanker Drop

Protect Taos Pueblo and Taos to the West

IMET ForecastingIMET Forecasting

Sanford FireSanford Fire

Data: Rick Stratton, SEM, Missoula Fire Lab

Sanford Fire Fuel

ENGLISH8 12 0 600 1700 54 87 50 20 75008 13 0 600 1700 52 88 50 20 75008 14 0 600 1700 52 88 50 25 75008 15 0 600 1700 57 87 50 27 75008 16 0 600 1700 56 81 50 23 75008 17 0 600 1700 57 81 50 20 75008 18 0 600 1700 53 81 50 21 7500

WTR Weather Stream File for FARSITE

IMET ForecastingIMET Forecasting

Regression Equations TechniquesRegression Equations TechniquesNational Fire Danger Rating National Fire Danger Rating Forecasts from local NWS Forecasts from local NWS Offices.Offices.

Multiple Regression for Grassy Mtn RAWS - Summer Min Eq

y=(.34A)+(0.037B)+(-0.0021C)+(0.62D)+2.3 R2=0.86

0

20

40

60

80

0 20 40 60 80

Boise Min Temp

Gra

ss

y M

in T

em

p

Grassy fcst

Fire-business driven fuel Fire-business driven fuel dryness prediction, tailoring dryness prediction, tailoring broad scale models to predict broad scale models to predict fuels’ receptiveness to fire.fuels’ receptiveness to fire.

DGEX vs. GFS DGEX vs. GFS (Model Downscaling)(Model Downscaling)http://wwwt.emc.ncep.noaa.gov/mmb/mmbpll/dgexhome.ops/http://wwwt.emc.ncep.noaa.gov/mmb/mmbpll/dgexhome.ops/

500 mbht/Vort

850 mbwind

AcknowledgementsAcknowledgements

NWS Mets and IMETs Chuck Redman, Coleen NWS Mets and IMETs Chuck Redman, Coleen Decker, Chris Gibson, Brent Wachter, Jim Decker, Chris Gibson, Brent Wachter, Jim Prange, Bob Servick, Julia Rutherford, Bernard Prange, Bob Servick, Julia Rutherford, Bernard Meier, Larry VanBussum, and Chuck Baker.Meier, Larry VanBussum, and Chuck Baker.

Predictive Services GACC Mets Terry Marsha, Predictive Services GACC Mets Terry Marsha, John Saltenberger and Tim Mathewson.John Saltenberger and Tim Mathewson.

NCEP’s Geoff DiMego.NCEP’s Geoff DiMego.

The National Interagency Fire Center Training The National Interagency Fire Center Training Branch.Branch.