Scorching, deadly fires that tore through Los Angeles apace last week were whipped up by furious winds that had barrelled in from the desert.
The blazes are still raging. And this week the so-called Santa Ana or “Devil” winds are back. This is what it could mean.
What are the Santa Ana winds?
Santa Ana winds are hot, dry winds that blow in from the northeast.
They pick up speed as they hit the mountains around LA, and send humidity levels plunging, further upping the fire risk.
Although investigators are still confirming the spark of each fire, these winds have largely been blamed for last week turning the wildfires into infernos that razed entire neighbourhoods to the ground.
Adding fuel to the fire has been the impacts of climate change, which is making the weather hotter and drier, creating tinderbox conditions that allow fires to balloon.
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Los Angeles has had no significant rainfall in over eight months, even during what is now supposed to be the wetter season.
How the Santa Ana winds fuelled last week
In the early hours of last Tuesday, weather chiefs issued a rare “particularly dangerous situation” red flag warning as they braced for violent winds.
It was “about as bad as it gets in terms of fire weather”, the National Weather Service (NWS) Los Angeles said.
How prescient that warning was.
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At 10.30am PST the first fire started in Palisades – the spark not yet determined. Over the next few days, wind speeds reached 99mph in places, five further fires broke out, together burning more than 40,000 acres and counting.
After the winds had died down on Thursday, firefighters over the weekend managed to extinguish three of the fires.
But on Monday, the two biggest blazes, Palisades and Eaton, were still raging, with less than half of their perimeters under control. The Hurst fire was also still ablaze, but almost contained.
When are the high Santa Ana winds back?
Worse still, on Monday winds picked up again, and the NWS issued another “particularly dangerous situation” red flag warning for 4am local time on Tuesday until noon on Wednesday.
Fears of further destruction rocketed, the wind threatening to reverse progress firefighters had made in containing the fires.
It will bring hot, dry north-easterly winds of 30-40mph, with gusts up to 65mph.
Tuesday will be the most dangerous day, fire behaviour analyst Dennis Burns warned at a community meeting on Sunday.
The warnings cover the areas of Calabasas and Agoura Hills, Eastern San Gabriel Mountains, Malibu Coast and Santa Clarita Valley.
“Critical fire weather is expected, so PLEASE have multiple ways of getting notifications in case of new fires,” NWS urged.
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What will the high winds mean for Southern California?
Although the speeds are unlikely to reach those of last week, they are enough to fan “extremely rapid spread”, warned Sky News’ meteorologist Chris England.
“Yes, the winds are coming back,” he said. “And it’s staying dry with the wind coming from the interior.
“It won’t be as windy as when the fires started, but that’s more than enough to ensure extremely rapid spread and difficult containment.”
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Joe McNorton, fire scientist for the European Centre for Medium-Range Weather Forecasts (ECMWF), said the moderate winds will “potentially [sustain] the risk of fire spread before conditions ease”.
Officials have tried to reassure worried residents, pre-positioning fire engines to be ready to respond to any new fires and deploying firefighters to patrol high risk areas.
LA County fire chief Anthony Marrone said: “All fire departments and all law enforcement agencies in the area will be prepared.”
Governor Gavin Newsom urged people to be “ready to evacuate if you get the order”.
