The Science Behind LAFD Fire Weather

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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 daily to determine the BI:

First, fuel moisture readings are taken at Fire Station 108 on Mulholland Drive, and communicated to the Division 3 office located at Fire Station 88 in the San Fernando Valley.

These fuel moisture readings are matched with predicted fire weather information (i.e. high/low temperatures, humidity, wind speed and direction) provided by a group of federal meteorologists at the Fire Weather Center (FWC) in Riverside, California.

This inter-agency group composed of California Department of Forestry & Fire Protection, Bureau of Land Management, the Forest Service and the California Emergency Management Agency, provides the data necessary for Los Angeles Firefighters to determine the Daily Fire Rating and local pre-deployment of resources.

Along with real-time weather surveys conducted by LAFD Division 3 personnel, the National Weather Service (NWS) web site is used to monitor current fire weather conditions in and near the City of Los Angeles.

National Weather Service information may be different from that provided by the Fire Weather Center. The National Weather Service may indicate a Red Flag Warning, whereas the FWC indicates a lesser rating i.e. Extreme or Very High.

When the National Weather Service and FWC information do not match, real time weather surveys and long-term predictions gain importance, as they are considered the best predictor of fire weather conditions in the City of Los Angeles.

The daily BI-levels are stated as a numerical value:
BI 0 to 37 = Low
BI 38 to 47 = Moderate
BI 48 to 110 = High
BI 111 to 161 = Very High
BI 162 to 211 = Extreme
BI 212 and above = Critical

Red Flag Alert days occur simply when the wind speed is 25 miles per hour or more and the relative humidity is 15% or less.

A red flag warning means that critical fire weather conditions are either occurring now... or will shortly. History has proven that a combination of strong winds, low relative humidity and warm temperatures will create explosive fire growth potential.

On Extreme, Critical and Red Flag Alert days the Los Angeles Fire Department pre-deploys resources into select Neighborhood Fire Stations serving brush areas. The specific stations/locations selected for pre-deployment are based on fire experience, area access and fire potential.

Republished with permission of Los Angeles Fire Department. View original article here.



Author:Brian Humphrey - PIO - Los Angeles Fire Department