About Those Infamous Winds Fanning California’s Flames

December 8, 2017

The always prescient Joan Didion described the Santa Ana winds—currently the driving force behind the devastating California wildfires—and their relationship to Los Angeles this way:

“Los Angeles weather is the weather of catastrophe, of apocalypse, and, just as the reliably long and bitter winters of New England determine the way life is lived there, so the violence and the unpredictability of the Santa Ana affect the entire quality of life in Los Angeles, accentuate its impermanence, its unreliability. The wind shows us how close to the edge we are.”

Now those winds have pushed the city and greater metro area over the edge, turning the landscape into a fiery hellscape. Winds gusting up to hurricane force have created some of the most dangerous fire conditions in 30 years according to Los Angeles’ fire chief.

This Santa Ana wind event is exceptional, but the winds themselves are a regular feature of life in Southern California from fall through spring. December and January are usually the peak of the wind season, which is usually driven by an atmospheric tug of war between weather systems over the Great Basin—the region that sits between the Sierras and the Rockies—and the Pacific Ocean, with California unfortunately caught in the middle.

The whole pattern starts in the desert when high pressure sets up over the Great Basin. That, by the way, is exactly what happened earlier this week as a monster ridge built over the region.

Winds circle the area of high pressure clockwise in what scientists call an anticyclonic flow. That air can eventually start to slip away from the high pressure, especially if there’s a low pressure system over the Pacific, and flow over the Sierra Nevada mountains and toward the coast.

Known as a katabatic wind, this type of wind can be found in various spots all around the world. In Northern California, they’re called Diablo Winds. In Alberta, they’re Chinooks. In Austria, they’re dubbed foehn winds. I could go on but you get the drift.

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