Examining Behavior of the 2017 Thomas Fire Using Polarimetric Radar (181)

Sean Luchs, NWS Houston/Galveston, Dickinson, TX

Rich Thompson, NWS Los Angeles



Recognizing and anticipating changes in fire behavior are critical to fighting wildland fire effectively and safely. Information in service of this comes to wildland firefighters from many sources: briefings, personal observations, communication with other firefighters, and communication with aviation resources. Weather data is also used, but is largely confined to direct weather impacts on the fire area. There has been some work in using radar and satellite to describe a fire's smoke/debris plume, but the descriptions have largely been limited to general observations of the extent of smoke impacts with little effort in a tactical evaluation of fire behavior. However, the Thomas Fire may have shown potential for using radar data to gain insights on fire behavior.

By the time of its containment in mid-January 2018, the Thomas fire was responsible for burning over 280,000 acres, the largest on record in California. It was also intensely destructive, consuming over 1,000 structures in the Wildland Urban Interface of Los Angeles. This location also made it easily recorded and well sampled by the National Weather Service's WSR-88D radars in the area. Video and radar data is used to investigate reports on December 16, 2017, of a plume collapse. There are indications that this collapse has a signature in differential reflectivity data. A patch of lowered differential reflectivity present near the fire's updraft diminishes with the plume collapse, and returns as a new plume returns. This demonstrates the possibility of using radar data as a way to alert firefighters to an impending threat to their safety and possible new erratic fire growth. More study will be necessary to determine how much lead time is possible, but speculate it may be similar to a tornado warning.