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Unit 9: Extreme Fire Behavior

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Firewhirl

The graphic below illustrates one firewhirl development situation. Here a fire is burning on the lee side of a ridge from the general winds. Solar heating has created thermals in the basin below the fire, and warm upslope drafts are feeding the fire. Wind eddies on the lee side of the ridge can offer the triggering mechanism to start the whirls. Fire whirls might remain mostly stationary for several minutes. They frequently might move upslope until they reach the top where stronger winds break up the whirls, or they can move downslope in the direction of the prevailing wind.

Firewhirl
Firewhirl development

We should mention here that dust devils or the smaller whirl winds develop under very similar conditions. The last factor, intense heat from a fire, is not always a requirement, as dust devils develop easily over desert lands, plowed fields, and other heat absorbing surfaces.

Copyright 2008, by the Contributing Authors. Cite/attribute Resource . admin. (2005, November 10). Unit 9: Extreme Fire Behavior. Retrieved January 07, 2011, from Free Online Course Materials — USU OpenCourseWare Web site: http://ocw.usu.edu/Forest__Range__and_Wildlife_Sciences/Wildland_Fire_Management_and_Planning/Unit_9__Extreme_Fire_Behavior_6.html. This work is licensed under a Creative Commons License Creative Commons License