How Santa Ana winds form
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How Santa Ana winds contribute to fires

1. Typically, strong high pressure moves across California and generates winds that howl through north-south canyons in places such as Malibu, sometimes downing power lines that ignite blazes.

Reporting and illustration by Paul Duginski / Los Angeles Times ()
2. When a high pressure dome exists to the east, winds become primarily northeasterly. High-pressure air moves toward low pressure, so lower pressure closer to the coast intensifies the force. This week, the low happened to move inland rather than along the coast. ()
4. Terrain makes the winds fickle. Mountain ranges block winds in some areas, particularly at lower elevations, even as strong winds are howling through other areas. ()
5. Winds seek out openings through the mountains, much like water would. Canyons and passes provide narrow openings that accelerate the winds like a nozzle on a garden hose does to water. ()