Event (5) Fire jetting out of lee-slope eddy away from main fire

Air Observer

From an ABC TV News Bulletin, from a Calfornia news helicopter. 119.7° 34.4° looking N at about 18:00 PDT 5th May 2009.

This photo of the Jesusita Fire in California shows two channelling events acting together to move the fire rapidly both downwind and cross wind. The right-hand edges of both events have dense smoke and active convection.
In both cases flames can be clearly seen emerging from the lee-slope eddy and “jetting” out. This is likely due to thermal expansion within the eddy, which also leads to ejection of embers which ignite the landscape downwind. Observation of jetting is diagnostic.

Implications

Phenomenon	Urgency	Indicated Red Flag Warning
Dynamic channelling	1	6) Channelling event
Deep flaming zone	?	2) Conditions conducive to plume-driven fire

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This material arises from work carried out by the HighFire Risk Project.

Material prepared by R. McRae September 2009.