What Rabbit Rules tells us about the Esperanza Fire

On 26 October 2006 a sudden, intense fire run on the Esperanza fire killed five fire fighters. The event was simulated by Rabbit Rules – an experimental recursive fire spread model– which has shown skill at simulating some extreme aspects of coupled fire/atmosphere behavior. The intense run was the outcome of four fire/fuel/atmosphere conditions: (1) a mostly flanking fire line with a small head fire component directed to blowing the fire down the east slope along much of the extent of the unnamed creek valley, (2) a change in fuels from mostly grass on the slopes to mostly chaparral in the valley, (3) maintenance of a head fire driven by easterly Santa Ana winds through grasses within the adjacent desert valley near Cabazon, CA, and (4) terrain-induced shifting of winds to blow from the northeast up the unnamed valley.

The run commenced when the head fire at the edge of the desert was drawn into the entrance of the unnamed valley and ignited chaparral there. The heat plume moving up-valley (southwest) from this fire set up a circulation that shifted winds to change the existing flanking fire into a head fire that ran down slope and ignited chaparral. Firebrands from these ignitions spread across the valley to ignite more chaparral and reinforced the existing circulation. This sequence of events spread up the valley as a chain reaction so that much of the valley was on fire within a few minutes. The intense run culminated at the valley end when the heat plume blasted past an octagonal house killing five fire fighters.

Results of the simulation including fire line history and time series of wind speeds will be presented.