Santa Ana winds are common in southern California during cooler months and have fueled many of the Golden state’s most ferocious wildfires. Here is everything you need to know:
What are the Santa Ana winds?
Santa Anas are dry, warm and gusty northeast winds that blow from the interior of southern California toward the coast and offshore, moving in the opposite direction of the normal onshore flow that carries moist air from the Pacific into the region.
How do they form?
Santa Anas are created by high pressure over the Great Basin – the vast desert interior of the west overlapping several states. The sinking air loses its moisture and flows in a clockwise direction toward southern California, where it must get past towering mountain ranges that separate the desert from the metropolitan region lining the coast. Like a slow-moving river that suddenly narrows and turns into rapids, the air speeds up as it squeezes through mountain passes and canyons, becoming drier and warmer as it descends.
Why do they increase wildfire danger?
Humidity levels often plunge to single-digit percentages during a Santa Ana wind. The extreme lack of humidity in the air causes vegetation – living and dead – to significantly dry out and become susceptible to fire.
The tremendous wind speeds can stoke any spark – from a fallen power line to a cigarette bud – into a rapidly spreading conflagration.
Santa Anas are linked to some of the worst wildfires southern California has experienced, including the Woolsey fire, which killed three people and destroyed more than 1,600 structures in November 2018, and the Franklin fire, which damaged or destroyed nearly 50 homes in the Malibu area.
How did they get their name?
A commonly accepted explanation is that the name is linked to Santa Ana Canyon in Orange county. Other theories persist, along with other nicknames including “devil winds.”