Santa Ana winds and record-breaking heat raise fire fears

Record-breaking temperatures, gusty Santa Ana winds and bone-dry conditions have Southern California bracing for a weekend of fire danger.

The National Weather Service issued a red-flag warning for a large swath of Southern California, including the mountains and valleys of Los Angeles, Ventura, San Bernardino, Orange and Riverside counties. The warning, which denotes the potential for rapid fire growth and extreme fire behavior, is in effect through 4 p.m. Saturday but could be extended into Sunday, according to the weather service.

Forecasters also were expecting red-flag conditions in Santa Barbara County above Montecito but said they’d last for only two to three hours Friday night, short of the six hours required for an official advisory to be issued.

Already by Friday morning, the wind had helped fuel two brush fires that grew to several hundred acres each.

The larger of the two broke out in the San Jacinto Mountains in Riverside County at about 1:15 a.m. Friday, burning through stands of pine trees and prompting an evacuation order for the community of Mountain Center.

By 6:30 a.m., the Bonita fire had grown to 600 acres and was about 5% contained, said April Newman, public information officer for the California Department of Forestry and Fire Protection and the Riverside County Fire Department.

“The wind definitely poses a challenge for us, especially with the Santa Anas and the red-flag warning that we have for the day,” Newman said. “That’s on top of the dry brush from the lack of waterfall that we’ve had this season.”

Wind gusts in the area of the fire could peak Saturday at 30 to 35 mph, said Bruno Rodriguez, meteorologist with the National Weather Service in San Diego.

Winds were expected to be even stronger further north in the Thousand Oaks area, where the Erbes fire ignited at about 5 p.m. Thursday and spread from 20 acres to more than 200 in less than an hour.

Fire crews had stopped the blaze’s progress by 9 p.m. at roughly 250 acres and expected to have it fully contained by Friday afternoon.

The weather service was recording wind gusts of 30 to 45 mph, with isolated gusts of 60 mph, across the L.A. County forecast area Friday but said they would likely diminish later in the afternoon before picking up again Saturday morning.

Though Santa Ana wind events are more typical in the fall and early winter, they can happen any time of the year with the right weather pattern, said Joe Sirard, meteorologist with the National Weather Service in Oxnard.

In this case, a large area of high pressure in the upper atmosphere was causing high pressure at the surface to build into the Great Basin, creating northeast winds across the area, he said.

“So it’s a warm upper-level high, and what that does is it causes the hot temperatures to develop down in the coastal valleys with the offshore Santa Ana winds,” Sirard said.

Unlike onshore winds, which bring in moisture as they blow from the ocean over the land, Santa Ana winds originate inland, gaining speed, warming up and drying out as they move from higher to lower elevations and squeeze through narrow canyons and passes.

Relative humidities plummeted into the single digits Friday in some areas, and they weren’t expected to recover much overnight, “which for fire agencies is a challenge,” said Mark Jackson, head meteorologist at the National Weather Service in Oxnard.

Temperatures were forecast to be 15 to 25 degrees above normal across Southern California on Friday, reaching into the high 80s and low 90s, with highs in the mid-90s possible in parts of Orange County and the Inland Empire, the weather service said.

On Thursday, the National Weather Service recorded a high of 91 degrees at Camarillo Airport and two other weather stations near San Diego.

“That was the warmest temperature in the nation yesterday, in the whole United States,” Sirard said. “And it’s likely that we’re going to have somewhere in our area be the nation’s hot spot again today. So if you like warm weather, this is the place to be this weekend.”

Camarillo Airport had already reached 88 degrees by 10:30 a.m. Friday, tying the daily record set in 1975, and appeared on track to approach the all-time record for January of 94 degrees, the weather service said.

Friday’s heat also was expected to meet or exceed daily records in downtown Los Angeles, Long Beach, Burbank and Santa Barbara, and at weather stations at UCLA and LAX.

Temperatures were expected to cool off slightly in some areas starting Saturday but remain 10 to 20 degrees above normal through the weekend.

Forecasters warned that another, even stronger wind event could start Monday night and bring wind gusts of 60 mph or higher, with isolated gusts of up to 80 mph possible in some areas.

A low pressure system is expected to drop down over Southern California, centered over Ventura, Los Angeles, Orange, San Bernardino and Riverside counties, Rodriguez said.

“Monday into Tuesday it’s looking very strong, likely the strongest so far this season,” he said of the winds.

Still, he said, for the San Diego forecast area, the fire danger from that weather event could be limited by slightly higher humidity, as well as a slight chance of precipitation late Tuesday into Wednesday in the mountains and lower deserts of the Coachella and San Diego areas. There was also a chance of some snow accumulation in the mountains, he said.

Jackson cautioned that even if the humidity rises to the 15% to 25% range or higher Tuesday, the L.A. area still could see red-flag conditions because of the winds, plus the fact that vegetation is dried out due to lower-than-average rainfall.

“Anytime you get wind speeds over 60 mph, you have that potential for very damaging wind gusts and the impacts that will go with that,” he said. “So this is a fairly significant wind event.”

The winds, which are expected to be strongest Tuesday, could extend down into the L.A. Basin, with gusts over 50 mph possible in downtown Los Angeles, he said.

The weather service warned of rough seas along the Los Angeles and Ventura County coasts, with a high surf advisory expected Saturday evening through Tuesday. West-facing beaches could see large breaking waves of five to eight feet Saturday and Sunday and six to 10 feet by Monday afternoon, Sirard said.

There also was concern about wind-driven waves crashing into east-facing harbors like Catalina Island’s Avalon.

“We always advise people to stay out of the water if possible and avoid going out on jetties and that sort of thing because you can get these rogue waves that come in and wash people off,” Sirard said. “It’s a very dangerous situation.”

Conditions are expected to become cooler and less dry by the end of next week. Longer-term National Weather Service forecasts show a greater than 50% chance of above normal precipitation in most of California through next Friday and into the middle of the following week, which Jackson called “encouraging.”

“We’re still quite a bit below normal for the season,” he said. “But this would be a very welcome change in conditions.”