Mudslides offer a preview of what could be a wet winter in Southern California

As heavy rain pelted Hollywood Burbank Airport on Thursday morning, the pilot of Southwest Flight 278 out of Oakland came over the intercom with a warning: The runway was short and wet. It was going to be a bumpy landing.

Paris Organist, a 31-year-old Oakland resident sitting in the front row, put up his foot to brace himself as the plane rolled off the end of the runway just after 9 a.m., its landing gear plowing into a concrete barrier designed to stop airplanes that overshot their mark. Mud splattered on the plane’s windows.

“We looked it up on Google Maps, and it showed we were almost to the road.… We noticed the plane had sunken into the ground,” Organist said.

At around the same time, 58 miles northwest at the California Highway Patrol’s Fort Tejon office in Lebec, Officer Jeff Burdick started hearing a gaggle of radio traffic about the 5 Freeway through the Grapevine: Crash. Spin-out. Another crash. Out the window he could see that it had started snowing heavily.

“It was just all of a sudden,” he said. “We looked up and were like, ‘Ah, crap.’”

The storm that pelted Southern California on Thursday flooded roadways, triggered mud and debris flows in the burn areas of Malibu and dumped several inches of snow on mountain passes, shutting down the 5 Freeway through the Grapevine for much of the day.

Eric Menjivar, a spokesman for Caltrans, said road crews were pelted with a simultaneous onslaught of issues.

“It’s one of those days where you’re like the GIF of the cat on the keyboard … that’s just typing on the computer really fast,” he said. “It caught a lot of people off guard. We were looking at the forecast, and it looked like we weren’t going to get hit too bad. This morning, all that changed.”

After a year of severely dry weather, a powerful storm such as the one that hit the Southland this week would typically be welcomed. But unprecedented fires over the last year have left hillsides from Montecito to Lake Elsinore highly vulnerable to mudslides during heavy rains.

So the deluge brought more than the usual dangers, and offered a preview for the season ahead if there are more powerful winter storms. While no one was injured on Thursday, a massive mudslide in Santa Barbara County earlier this year — just weeks after the massive Thomas fire swept through — killed more than 20.

In Riverside and Orange counties, mandatory evacuations were ordered for areas that had burned in this summer’s Holy fire, with residents in the Lake Elsinore and Trabuco Creek areas told Thursday afternoon to leave their homes.

Pacific Coast Highway was closed for several hours because of mudslides in the Woolsey fire burn scar in Malibu. At least one vehicle, a silver Mercedes sedan, was stuck in a thick layer of sludge as crews removed mud and rocks from the road.

“First the fires, now the mud,” said Gunter Renshaw, who moved to Malibu five months ago.

The storm, which came out of the Gulf of Alaska, is a “nice little jump-start on the rainy season,” said climatologist Bill Patzert. California, he said, “has been in a state of fire fatigue. This will probably give us fire relief for the rest of the season.”

Since the start of the water year on Oct. 1, downtown Los Angeles has received more than 4 inches of rain — more than the average amount of precipitation for this time of year and significantly more than last year, when about 1/10 of an inch of rain fell.

The last water year — Oct. 1, 2017, to Sept. 30, 2018 — was the third driest in downtown L.A. since records began in 1877, dropping just 4.72 inches — about 32% of the average rainfall of 14.93 inches.

Conditions were so dry last year that the Thomas fire, which began on Dec. 4, 2017, whipped out of control by Santa Ana winds, destroying more than 1,000 structures.

By 4 p.m. Thursday, downtown Los Angeles had received 2.09 inches of rain over the preceding 24 hours.

There are a couple of reasons why it’s hard to say whether the rest of the season will be rainy.

Not only is there a “wannabe” El Niño in the Pacific Ocean along the equator, a weather phenomenon that can cause a series of subtropical storms to hit California, Patzert said, but there’s also a “blob” of warm water in the northeastern Pacific Ocean, which in years past has reinforced a drought-worsening ridge of high pressure that diverts storms away from the West Coast and into the central United States.

“It’s a rematch of the blob versus El Niño,” Patzert said. “Most forecasters are being cautious about January, February and March, which are usually our wettest months.”

Thursday’s rain was more intense than expected. On Wednesday morning, the National Weather Service’s office in Oxnard tweeted that the rain event was expected to produce light to moderate rain, and the threat of mudslides and debris flow was expected to be “minimal to none.”

But the storm that meteorologists were trying to forecast is a notoriously difficult one to pin down, the weather service said. It’s known as a “cutoff low” in which part of the jet stream — the river of air in the upper atmosphere upon which storms ride west to east — is cut off from the main flow of air, producing a counterclockwise movement of winds and low pressure that’s home to the storm.

Forecasters had thought that the storm-producing area of low pressure would stay farther off the coast, producing lighter rainfall in Southern California. Instead, the cutoff low moved directly over the area, producing more intense rain over the region, lightning in Orange County, and 2 to 3 inches of snow over the 5 Freeway through the Grapevine, according to the weather service.

The rain caused spin-outs and dozens of crashes on freeways and local streets throughout Los Angeles County. A roadway in Encino that was flooded with 2 feet of water stalled cars and required firefighters to rescue stranded motorists.

Corona del Mar High School in Newport Beach canceled classes and sent students home early after the campus flooded.

The 5 Freeway in the Grapevine was shut down after snow blanketed the mountainous area. About two dozen commercial trucks got stuck and had to be towed off the roadway, said Caltrans spokesman Jeremiah Teves. As they used snowplows to clear the roadway, Caltrans crew dubbed it “Operation Snowflake,” Teves said.

The storm was expected to linger through early Friday, forecasters said.

Times photographer Al Seib and Times Community News staff writer Andy Nguyen contributed to this report.