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Exceptional Santa Ana winds behind devastating LA fires

Abnormally strong Santa Ana winds caused ferocious fires to spread through parched areas of Southern California in the last 48 hours, destroying homes around Los Angeles.

The Santa Ana winds refer to seasonal northeasterly winds that periodically blow dry air through coastal areas of Southern California around this time of year. They develop when air descending from the Sierra Nevada Mountain Range becomes warmer and drier as it flows down towards the coast, being enhanced further by the San Gabriel and Santa Monica Mountains.

Under certain synoptic conditions, the Santa Ana winds can be exacerbated by breaking mountain waves, which occur when even stronger upper-level winds rapidly descend towards the surface on the leeward side of a mountain range.

This dangerous combination of Santa Ana winds being bolstered by breaking mountain waves caused the spike in dangerous fire weather that affected Los Angeles and other areas of Southern California this week.

Image: Modelled wind gusts at 4am Los Angeles time on Wednesday, January 8.

Wind gusts of up to 100 mph (161 km/h) were recorded in the San Gabriel Mountains to the east of Los Angeles early on Wednesday morning. Gusts of 84 mph (135 km/h) were also recorded at the Hollywood-Burbank Airport on Tuesday night.

Malibu, California is burning all along the PCH after explosive Santa Ana winds overnight on the backside of amplifying upper system - pic.twitter.com/1C0FLFENDm

— Reed Timmer, PhD (@ReedTimmerUSA) January 8, 2025

In addition to these powerful winds, the dryness of the air and landscape contributed to the destructive fires. Large areas of Southern California are currently in moderate to severe drought.

Images captured from the ground showed how quickly flames were able to spread across the dry landscape, scorching tress and buildings alike. Satellite images also revealed the massive scale of the fires from above.

Video: Visible satellite imagery showing the Palisades and Eaton fires in Los Angeles on Wednesday, January 8, 2025.

As of 9pm local time on Wednesday, the two largest fires in Southern California – the Palisades and Eaton fires – were uncontained.

Fortunately, the strongest winds have now passed and wind speeds are expected to reduce further through Wednesday night. However, another surge of Santa Ana winds is expected to occur on Thursday, but without the support of a breaking mountain wave it is expected to be weaker than the surge earlier in the week.

Visit https://www.fire.ca.gov/ for the latest information on fires burning in California.