Computational Fluid Dynamics (CFD) technology has been used to model wind speed and direction in mountainous terrain at a relatively high resolution compared to other readily available technologies. The process termed "gridded wind"; is not a forecast, but rather represents a method for calculating the influence of terrain on general wind flows. Gridded wind simulations are typically produced at resolutions of 100 m using laptop computers. Resolution is limited only by elevation data resolution and computer memory. Initial comparisons between simulated winds and measured average wind speeds and directions for specific locations indicate excellent agreement. Results suggest that as the upper air wind speed increases the relative magnitude of uncertainty in the simulated winds decreases. The modeled winds generally seem to be most accurate for simulation scenarios associated with large scale strong pressure differences such as cold front passage, Foehn (Santa Ana), and onshore/offshore winds. This high resolution wind information has proven useful for identifying areas and/or conditions around a fire perimeter that may produce high fire intensity and spread rates and for identifying specific locations where fire spotting might occur. Currently the output from the process can be summarized in the form of a shaded relief map with wind vectors overlaid on the terrain image, GIS shape files, and custom wind direction and speed files that can be utilized by the FARSITE fire growth simulation program. The accuracy of FARSITE fire spread predictions is improved in the few cases where gridded winds have been used.

[This publication is referenced in the "Synthesis of knowledge of extreme fire behavior: volume I for fire managers" (Werth et al 2011).]