Devastating wildfires continued to burn across the Los Angeles metropolitan area on Friday, prompting mandatory evacuations and school closures across the region. There is little opportunity for relief next week; conditions will remain conducive to the spread of existing wildfires and the starting of new fires as gusty winds persist amid unusually dry conditions.
Officials reported five major fires burning in the Los Angeles area as of Friday morning. The Palisades Fire in Pacific Palisades and Malibu has burned more than 20,000 acres, while the Eaton Fire in Altadena has grown to more than 10,000 acres. At least 10,000 buildings are believed to have been destroyed across Los Angeles, and 10 people were killed.
Favorable fire weather requires dry vegetation, low humidity and strong winds. The combination of these ingredients makes fires easy to start and spread quickly; it was this dangerous mix that allowed the Palisades and Eaton fires to spread beyond any crew's ability to control earlier this week.
Firefighters have since been able to bring the blaze under control with the help of out-of-state reinforcements, replenishing hydrant water and reduced wind speeds. (Earlier this week, Santa Ana’s seasonal winds not only caused fires to spread rapidly, but also sometimes prevented firefighting aircraft from using water and retardant chemicals to control the blazes.) The bad news is that those winds may now become even more dangerous. It's about to pick up again - and on all other fronts, things are unlikely to turn in firefighters' favor anytime soon.
The National Weather Service's Storm Prediction Center, which issues fire weather forecasts, said the risk of fires across Los Angeles will remain high through the weekend.
We may see two milder Santa Ana wind events over the next few days - one early Sunday and another possibly Tuesday. These wind gusts could encourage the spread of existing fires and spark additional fires.
Santa Ana wind events occur when there is a pressure difference between the Great Basin (a large swath of land in Nevada and Utah) and the coastal communities surrounding Los Angeles.
Meteorologists often use the air pressure difference between Las Vegas and Los Angeles to predict these winds. Stronger air pressure differences can create stronger winds that blow toward the coast, fueling existing wildfires. This is something they predict we may see again in the coming days.
Vegetation in the area will also continue to be unusually dry. It's the middle of Southern California's rainy season, but it's nowhere to be found. Los Angeles International Airport experienced its third wettest February on record last year, with just 0.03 inches of rain falling at the airport since early last summer.
Although mid-January is prime rainy season time for Los Angeles, there is little hope of meaningful rainfall over the next week and a half. The National Oceanic and Atmospheric Administration's Climate Prediction Center announced Thursday that we have officially entered La Niña, a pattern of cooler-than-normal water temperatures in the Pacific Ocean around the equator. Atmospheric changes caused by La Niña force the jet stream northward across the eastern Pacific, diverting storms to Canada's west coast instead of the western United States, leading to rain shortages in states like California.
At this point, the main storm track across the Pacific will remain near the Gulf of Alaska through mid-January, leaving little chance for rain to extend as far south as Southern California.
Forecasters expect weak La Niña conditions to persist into late winter, with the pattern likely to disappear in the spring. Unfortunately, this timing may coincide with the start of the dry season in Southern California.
That's not to say we might not see a chance for rain in the coming months. However, there will be almost no rainfall until at least mid-January, which will leave vegetation across the region unusually dry. The continued risk of new and additional fire growth will depend on the onset of low humidity and gusty winds, while any additional Santa Ana wind events could become hazardous in the coming weeks.