S. California faces fire threat from Santa Ana winds
High fire danger is forecast for Southern California over the Thanksgiving holiday, as Santa Ana winds bring dry, gusty conditions from Ventura to San Diego through Friday.
“This is a critical period with multiple days of Red Flag conditions,” the National Weather Service in Los Angeles wrote in a forecast discussion. “The public needs to be extra cautious with anything that could start a fire.”
The service described the event as the strongest of the season so, with gusts of up to 70 mph, along with humidity percentages into the single digits. Given the threat, Southern California utilities are considering cutting power to nearly 200,000 customers to prevent their equipment from sparking a wildfire.
The winds could impact holiday travelers on major interstates that run through coastal mountains and mountain passes, according to the National Weather Service in San Diego.
“Those living near fire prone undeveloped areas, like the national forests, should make or review the family plan including what to take and evacuation routes in the event of an evacuation order is issued or a nearby wildfire threatens,” wrote the weather service in Los Angeles in a forecast discussion.
The renewed fire weather marks a turnaround from October’s atmospheric river, which brought extreme precipitation to Northern California, but not quite enough rain to end the fire season farther south.
“October was very wet — unusually wet — and that bought us about three to four weeks,” said Alex Tardy, warning coordination meteorologist at the weather service in San Diego.
However, November has been mostly dry and punctuated by several rounds of warm Santa Ana winds, which at times have brought record-breaking temperatures to the coast, quickly drying out vegetation and nearly erasing the benefits of earlier autumn rains.
The region saw a relatively quiet summer, even as bone-dry forests went up in flames in Northern California and the Sierra.
“We expected quite a bit of fire activity in Southern California — it didn’t materialize,” Tardy said.
Fire meteorologists attribute the slower season in part to sparse growth from a dry winter and spring.
The region did not see a “superbloom” of flowers, grasses and weeds that had helped to fuel recent fire seasons.
But explosive fires were possible where winds coincided with enough fuel to burn. That was evident in September’s Alisal Fire in the Los Padres National Forest near Santa Barbara.
It was also apparent in the forests of the southern Sierra Nevada, which saw its driest water year on record at only 9.9 inches. Nearly 20 percent of giant sequoia trees are estimated to have been killed by severe fire in the region over the last two years.
Santa Ana winds are most frequent and strongest during the winter months, and climate outlooks aren’t promising relief from the warm, dry weather just yet.
“The dice are loaded for dry conditions to continue for most of the West, especially for Southern California,” said Michael DeFlorio, a research analyst at the Center for Western Weather and Water Extremes at Scripps Institution of Oceanography in San Diego.
A number of forecast models are favoring dry weather for Southern California and the Southwest at least for the coming weeks, and potentially for the bulk of the winter season. These include models that predict atmospheric river activity and cutting-edge “machine learning” models developed at Scripps in collaboration with the NASA Jet Propulsion Laboratory, in addition to outlooks provided by the Climate Prediction Center.
The emerging La Niña, which is predicted to strengthen into the winter, is a key driver of the dry outlook, but it’s not the only one.
The current configuration of sea surface temperatures in the Pacific can promote high-pressure ridging that diverts the storm track.
This kind of “blocking” pattern led to back-to-back dry winters in the West in 2020 and 2021. It’s also driving the dry spell right now, as strong storms are directed far to the north into Canada and the Pacific Northwest.