Santa Anas a particular threat in some Southern California areas

Why does Malibu seem to erupt in flames every fall, while most of Los Angeles, which has its share of houses clinging to brushy hillsides, does not?

The reason, according to a new study, is blowing in the wind.

Researchers have developed the first high-resolution map of Santa Ana wind events, showing that the hot, dry blasts don't sweep uniformly across the Southland and that the danger of large, wind-whipped wildfires is therefore greater in some parts of the region than others.

Guided by local topography, the seasonal Santa Anas follow certain corridors to the sea, consistently skirting other areas.

"Most people, think, 'Ah, it's a Santa Ana day, Southern California is in trouble,' and that is true," said Max Moritz, the study's lead author and co-director of the UC Berkeley Center for Fire Research and Outreach. "But there is much more spatial difference in that story, much more diversity."

The paper, published February in the online version of Geophysical Research Letters, includes a map marked with distinct bands outlining the favored Santa Ana routes.

"The Santa Monica Mountains and the Malibu area are just hammered," Moritz said. "Then the whole L.A. Basin to the south of there is actually in a sheltered window. You go farther south and you get another big band of high fire danger" in the Laguna Hills area of Orange County and then another in eastern San Diego County.

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--Bettina Boxall