Wildfire risk has returned to Southern California with the arrival of the strongest Santa Ana wind event of the season. Just a week ago, a potent winter storm dropped several inches of rain on the region as part of a cold, wet pattern that seemed sure to draw fire season to a close. But skies quickly cleared, and the weather changed on a dime.
The National Weather Service in Los Angeles warned of the threat of wind damage, power outages and wildfires Wednesday as dry and roaring Santa Ana winds bear down.
“If (a) fire ignition occurs there could be rapid spread of wildfire that would lead to a threat to life and property,” the Weather Service wrote.
Although last week’s rain should help to limit the spread of any fire that occurs, the strength of the winds and bone-dry air have forecasters concerned.
Peak gusts ranging from 60 to 75 miles per hour were expected Wednesday, with isolated gusts up to 95 mph in the very high terrain. Early Wednesday morning, a wind sensor on Magic Mountain Truck Trail, 23 miles north of Los Angeles at an elevation over 4,500 feet, clocked a 102 mph gust.
Rich Thompson, a fire weather meteorologist with the Los Angeles National Weather Service, said in a tweet that this week’s Santa Ana winds are dangerous, despite recent rain.
“This time of year, my mantra ‘wind trumps everything’ still holds true,” he wrote, referring to wildfire danger. “Be ready.”
Winds are blowing “offshore” from the north and northeast as a strong high pressure center over Nevada and Utah sends air rushing toward lower pressure off the California coast. The surface pressure difference between Los Angeles and Daggett, a town about 100 miles to the northeast, is used to estimate potential wind strength. That difference is expected to be “well above the 97th percentile for this time of year and would be one of the stronger offshore gradients we’ve seen in quite some time,” the Weather Service in Los Angeles wrote.
A red flag warning for high fire danger was in effect for Ventura County and western portions of Los Angeles County until 7 p.m. Wednesday.
“That whole area is very wind-prone. They should see quite strong winds into Wednesday,” said Ryan Kittell, a meteorologist with the National Weather Service in Los Angeles.
This region also had less rain in the recent storm – under an inch for much of Ventura County – and has generally missed storms this autumn that have soaked other parts of Southern California.
“Usually five inches everywhere is a starting point for fire-season-killing rain,” Kittell said. “We’re close to that in some areas but not quite (there).”
More time and more rain are needed to mute fire danger into the winter, he said.
“The plants that are still living – they really haven’t had much time to soak up moisture from the soil,” he said. Meanwhile, leaves and other dead plant debris on the ground are drying out quickly after last week’s storm.
That trend will continue with another Santa Ana event expected this weekend.
South and east of Los Angeles County, recent soaking rains have dampened fire danger considerably, particularly in inland mountain areas. However, the landscape isn’t yet as green as it would be later in the winter, and coastal parts of San Diego and Orange counties still face an “elevated” fire weather threat Wednesday.
“We do have potential for some fire growth if there are ignitions in the right sensitive area,” said Alex Tardy, the warning coordination meteorologist for the National Weather Service’s San Diego office. “We have another Santa Ana following this for the weekend, so we need to consider the significant drying of fuel that will occur after Wednesday.”
La Niña typically brings long breaks between storms for Southern California, as well as an amplified jet stream that can lead to windy patterns like the one bearing down this week, he said. With the core winter months predicted to be drier than normal, it could be touch-and-go for wildfire risk through the cold season.
“We are not out of fire season, even though the event last week was much wetter than most November storms and it was widespread,” Tardy said.
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