The region's topography conspired with the wind to thwart fire-suppression efforts. Steep canyons were largely inaccessible to ground crews. As the blazes raced uphill they grew more intense, consuming dense chaparral dried by drought. Flames as high as 80 feet, throwing off temperatures near 1,200 degrees, then ignited another typical Southern California fuel: canyon-top homes.
"That's where people want to live, and that's where the fire goes," said L.A. County Fire Chief Michael Freeman on Monday night, squinting up at hills obscured by smoke. "It's what we always see."
The Porter Ranch fire burned in an area that has repeatedly been scorched by wildfires driven by fierce Santa Ana winds.
"If they anchor themselves in the Santa Susana Mountains they seek to cross the 118 Freeway. . . . It is a historic path," said Los Angeles Fire Department spokesman Brian Humphrey. "The fire wants to go to the coast."
In the fall of 1993, 1982 and 1970 flames carved a path of destruction across the Santa Monica Mountains from the San Fernando Valley to the Pacific Ocean, just as fire officials feared they might again this week.
A history compiled by the Santa Monica Mountains National Recreation Area shows a fire corridor running roughly from Santa Susana Pass near the 118 west of Chatsworth, down Malibu Canyon to the sea.
One spot has burned 12 times since 1925 and may have burned a 13th time this week, said Robert Taylor, who prepares fire maps for the recreation area.
Two UC researchers who are mapping Santa Ana wind corridors in Southern California say the Santa Susana Pass area experiences some of the fiercest gusts in the region.
"That's where the winds are the strongest," said Alex Hall, a UCLA associate professor of atmospheric and oceanic sciences.
Santa Anas blow when desert winds push down canyons over passes and low mountains, warming and gaining speed along the way.
Hall likened the passes to holes in a bowl that allow the desert air to escape.
Fires have historically raged in two other Santa Ana corridors, in Orange and San Diego counties.
"It's really a striking pattern," said Max Moritz, co-director of the UC Berkeley Fire Center, who is working on the wind-mapping project with Hall. "Our preliminary work shows that these corridors line up well with fire history patterns, fire frequency and fire size."
