Fires that have been raging in the Los Angeles area for a week are at risk of intensifying as intense winds of up to 70mph fan the flames.
At least 24 people have died in the wildfires, more than 100,000 displaced, and over 12,000 homes destroyed or damaged, with entire neighbourhoods reduced to smouldering ash and piles of rubble.
Anticipating the Santa Ana winds – which are known for aggravating wildfires in Southern California – more than 8,500 firefighters attacked the two biggest existing wildfires from the air and on the ground, aiming to prevent them from spreading.
With much of Los Angeles and Ventura County set to experience 50-70mph winds on Tuesday and Wednesday, the National Weather Service put out a red flag warning, marking a rare “particularly dangerous situation”, while the US Storm Prediction Centre warned of “extremely critical” conditions.
Faced with the prospect of new fires igniting and existing ones worsening, Los Angeles City Fire Department chief Kristin Crowley told local residents: “This setup is about as bad as it gets. We are not in the clear.”
Here, Yahoo News takes a look at why the Santa Ana winds have such an influence over California’s wildfires.
What are the Santa Ana winds?
NASA’s Aqua satellite captured this image during wildfires in southern California in 2017. The red thermal imaging shows the fires, while the plumes of smoke are pushed out to see by the Santa Ana winds. (Nasa)
The Santa Ana winds, also referred to as the “devil winds”, are dry and powerful winds that originate inland and blow down the mountains towards the coast of California coast.
They pick up as high pressure builds over the Great Basin, which spans nearly all of Nevada, much of Utah and parts of California.
If there’s a low-pressure system along the coast, then the air will flow west. The more extreme the difference in pressure between both systems, the faster the wind will blow.
The region sees about 10 Santa Ana wind events a year on average, according to the University of California, typically between autumn and January.
The atmospheric event fuelling the LA fires isn’t a typical Santa Ana downslope event. Instead, powerful winds are blowing off the back of a storm system over the lower Colorado River Valley and being amplified by what scientists call a “mountain wave” event.
“When those conditions line up perfectly, it does behave just like a wave in the ocean, when the winds flow over the mountains and then come crashing down on the other side,” scientist Paul Schlatter with the National Weather Service in Boulder, Colorado, told Reuters
When conditions are dry, such as now, the Santa Ana winds pose a serious fire hazard.
Why have they propelled the LA fires?
Homes and cars left barren in the Pacific Palisades neighbourhood of Los Angeles. (Getty Images)
As the winds blow downslope from the top of the San Gabriel Mountains, they become drier and hotter, often with hardly any humidity at all.
California has experienced very dry conditions with very little moisture over the past few months, and the lack of moisture on vegetation and these powerful winds create tinderbox conditions.
“It’s very hard to extinguish a fire under these conditions… when the wind is blowing like this, there’s very little chance of stopping it until the wind subsides,” writes California research ecologist Dr Jon Keeley.
Senior hazard scientist at information service provider Dr Tom Jeffery said: “The Santa Ana winds that are currently driving these fires occur periodically, but the most recent winds are exceptionally strong, with reported speeds of 50 to 60 mph and greater.
“This not only drives the fires and embers but also inhibits flying the tanker aircraft and helicopters used to suppress the fires.”
A study published in 2021 looked at Santa Ana wind events over the past 71 years and found that while there was roughly the same amount of activity through the years, the timing is shifting from fewer events in September and more in December and January.
Where are the LA fires still burning?
Workers restoring infrastructure along a row of destroyed properties in Pacific Palisades. (AP)
As of Tuesday evening UK time, there were four major fires still burning in the Los Angeles area
The most recent of the blazes, the “Auto Fire”, has only recently ignited west of the city in Ventura County and has burnt 56 acres so far.
Closer to LA, the Palisades Fire, which has been raging for a week now, is still only at 17% containment, according to the California Department of Forestry and Fire Protection, and has burnt 23,713 acres.
The Eaton Fire, northeast of downtown Los Angeles, containment is at 35%, having burnt 14,117 acres, while conditions are looking more promising for the Hurst Fire northwest of the city, with containment now at 97%.
Firefighters fear the strong Santa Ana winds blowing towards the coast could undo their progress, with state authorities pre-positioning fire crews in anticipation of reignited blazes.
“We are giving this fire everything we’ve got” Los Angeles County Supervisor Lindsey Horvath told a press conference on Tuesday.
“This is a particularly dangerous situation, from now through tomorrow, the strongest winds will be this evening, and we ask everyone to get prepared now to evacuate.”
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