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Fewer red-flag fire warnings likely amid sweeping changes by National Weather Service

April 16, 2010 |  1:56 pm


The National Weather Service announced significant changes to the way forecasters issue red-flag fire warnings, in a move that could mean fewer such alerts for fire-prone areas stretching from Santa Barbara to San Diego.

The changes were prompted after officials determined that the current red-flag protocols were not always the most accurate precursors to major fires.

For example, the NWS office in San Diego issued a warning during a period of low humidity prompting fire departments to marshal resources even though officials concluded that the fire danger was fairly limited without strong winds. By contrast, large fires in Los Angeles County could start without high winds, pointing out another vulnerability. That was the case with last year’s Station Fire, which was sparked during a period of high temperatures but no winds.

The new red-flag warning system is meant to be more selective and will also take into account local geography and terrain. San Diego County, which is highly vulnerable during strong winds, will have a different criteria than L.A.’s foothills and mountains.

Largely because of steeper terrain and thicker vegetation, the northern part of the Southland, including L.A. and Santa Barbara, can burn rapidly with little or no wind as long there are dry conditions. In the past, forecasters in the L.A. area issued red-flag warnings as long as the relative humidity dipped below a certain point. Now, for the first time, there will be a wind component, but only a relatively breezy 15 miles per hour.

But as the huge Station Fire in L.A. County proved last year, wildfires can rage here even with virtually no wind. That’s why forecasters will still have a lot of discretion to issue red-flag warnings, even if all the general guidelines are not met, said Mark Jackson, a meteorologist for the National Weather Service in Oxnard.

“We hope to reduce warnings for conditions we learned don’t produce large, damaging fires,” he said. The San Diego office began putting the new guidelines into effect this week; the Oxnard office is expected to do so by June.

-- Hector Becerra

Photo: The Station Fire plume seen from downtown L.A. Credit: Los Angeles Times