FlamMap Wind Grid Files

FlamMap runs can use gridded inputs for the speed and direction wind variables. These two grids can be generated by external computational fluid dynamics or weather modeling software and saved as ASCII grid or GeoTIFF format files before you can use this option. You can also save the grids from a previous FlamMap run that used the Wind Ninja Option.

Farsite can utilize external gridded winds using an Atmosphere (.ATM) file.

Data Units

Data units are the same as those used for other wind stream input options in FlamMap:

Wind Speed MPH @ 20 foot, or km/h @ 10m (integer)
Wind Direction Azimuth Degrees (integer)

Wind adjustment factors (WAF) are calculated the same for gridded inputs as for stream inputs. The exact method is described with equation #44 in Finney (2004).

Resolution and Registration

Each of the two gridded inputs must be,

the same cell size and extent,
in the same datum and projection as your landscape file, and
at a minimum the same extent of the analysis area.

When using the stand alone WindNinja application best practice is to use your landscape file as the input.

Direction ASCII Grid Example

Example of wind direction grid.

The speed and direction grids are input to FlamMap using the Inputs tab in the "Runs:" dialog box.