The December forest fires are already a reality

This story originally appeared in High Country News and it is part of the Climatic desk collaboration.

In Southern California, December wildfires are somewhat rare, but not completely out of the ordinary. And this year, extremely dry conditions and strong Santa Ana winds created the perfect recipe for dangerous late-year fires.

On the night of December 9, the franklin fire sparkled in the hills above Malibu, tearingh about 3,000 acres in just 24 hours. As of noon on December 12, the fire was less than 10 percent contained, burning just over 4,000 acres and destroying at least seven structures.

Last month, the mountain fire it ignited under similar conditions in nearby Ventura County and grew to 1,000 acres within the first hour. In two days there were more than 20,000 acres; 240 structures were destroyed before firefighters contained them in early December.

And it hasn’t rained yet, not since the mountain fire or all fall.

It’s true that the Santa Ana winds (dry winds that blow from the high desert toward the coast and bring low humidity, sometimes below 10 percent) routinely increase in the fall and winter. But what is less normal is the lack of precipitation. fascinating Southern California at this time, although the region is not technically in a drought still.

A weather station in downtown Los Angeles has recorded only 5.7 inches of rain this year, and not even a quarter of an inch has fallen in December, which is typically the middle of the region’s rainy season. Most years would have seen three or more rainy days by then, enough to curb some of the wildfire risk; about 90 percent of the region’s rainfall arrives between October and the end of April.

“We are still waiting for the start of the rainy season in that part of the state, which would significantly wet fuels and end the threat of large fires,” he said John Abatzoglouprofessor of climatology at the University of California, Merced.

In wetter years, the windy season presents a lower risk of fire. But now, “when ignitions and wind collide,” as Abatzoglou said, the landscape is primed for fire. The dry grass and bushes are ready to burn, and the Fire danger The Los Angeles County Fire Department’s forecast on Dec. 11, the day the fire grew significantly, was high or very high throughout the Los Angeles Basin, Santa Monica Mountains and Santa Clarita Valley. “It hasn’t rained yet this season in Southern California,” he said. Daniel SwainUCLA climate scientist. “That’s the key. “That’s the real trick.”

Strong winds coinciding with bone-dry vegetation are not just a problem for Southern California. Dry conditions increase the risk of wildfires across the country, during the east coastthe spring and fall fire seasons, for example. And winter fires have broken out elsewhere in the West: Colorado’s rapid advance Marshal fire It broke out on December 30, 2021, and went from a small grass fire to a suburban conflagration, ultimately burning more than 1,000 homes, in just one hour.