Three brushfires that occurred over Sunday and Monday in the Malibu area have everyone from residents to firefighters on high alert.
and strong winds have combined to cause two Red Flag Warnings in the past two weeks and, with Southern California in the midst of an historic dry spell, the fire warnings are expected to persist. Low humidity, warm weather
Many Malibu residents are familiar with the signs along Pacific Coast Highway that warn of the current level of fire danger in the city (“high,” “low,” or in the case of a Red Flag, “extreme”). But how do firefighters gage fire danger?
Bryan Humphrey, spokesman for the Los Angeles Fire Department, recently answered that question in an article posted to the department’s website and reprinted below. While it referred specifically to the City of Los Angeles, the same methodology is used in Malibu and elsewhere:
How are decisions made by the Los Angeles Fire Department to pre-deploy resources on days of high wildfire hazard?
The answer is science.
The LAFD utilizes a Burning Index (BI) to determine the department’s commitment to pre-deploy resources. A number of procedures occur each day to determine the BI in Los Angeles.
First, dead vegetation fuel moisture readings are taken in the early afternoon at Fire Station 108 on Mulholland Drive near Coldwater Canyon, and communicated to LAFD’s North Division Headquarters located at Fire Station 88 in the San Fernando Valley.
Second, a group of federal meteorologists at the Southern California Geographic Area Coordination Center (SCGACC) in Riverside, California provide a “fire weather forecast” consisting of a predicted high temperature, low relative humidity, wind speed and direction for the next day.
Third, historical data (high/low temperature, high/low relative humidity and hours of rainfall in the last 24 hours) is mixed into the brew.
All of this information is fed into equations that make up the National Fire Danger Rating System (NFDRS). The result is the BI. Theoretically, fire danger is elevated when BIs reach high values.
On days of Extreme Fire Danger, the Los Angeles Fire Department may pre-deploy resources at select Neighborhood Fire Stations in-and-near areas prone to wildfire.
Not all forecasts become reality, so LAFD North Division staff conduct real-time weather surveys, monitor Remote Automated Weather Stations (RAWS) in and near the City of Los Angeles and consult the National Weather Service (NWS) to stay abreast of fire weather conditions and forecasts.
The NWS and SCGACC may come to different conclusions on the forecast as well, based on which computer model each agency trusts. Ultimately, the LAFD makes decisions on pre-deployment based on all of these inputs – with a lot of experience mixed in.