Shifted Storm Track Pounds Sierra, Leaves San Diego with Meager Rain

February in San Diego came on like an entire pride of lions. Six stormy days into the month, the city had already recorded more rain than it normally gets all of February.

Since Feb.10, however, the month has behaved more like a timid kitten. Storms have flirted with the region, but San Diego mostly has been on the outside looking in. Below-normal rainfall has fallen the last three weeks.

March is expected to roar into the mountains of Northern California with the biggest storm of the year. A rare blizzard warning has been issued for the Sierra, which could see as much as 10 feet of snow at the highest peaks by Sunday. Complete white-out conditions Friday could reduce visibility to zero and make travel impossible. Some highways are already closed, and most ski resorts have or will shut down, too. Snow could fall as low as 1,000 feet for the first time all season. 

In San Diego County, the next storm should arrive with more of a meow than a roar. Strong winds are expected in the mountains, but from late Friday through Sunday, forecasters predict no more than a quarter inch of rain will fall at the coast in the North County, and likely less than a tenth of an inch in the South County. 

But with apparent assistance from El Niño, San Diego didn’t miss the rainfall parade this year. Thanks to the wet start, this was the city’s wettest February in 19 years, with more than twice the usual amount of rain. And this weekend’s storm, meager as it’s expected to be locally, could still lift the city’s rainfall total to near or above normal for an entire year. 

The state as a whole appears to be headed for a rare, second-straight wet year (the first time since 2010 and 2011), which is making water managers happy and turning talk of drought and water rationing into a distant memory. 

While San Diego mostly dried out the second half of February, powerful storms continued to pound much of the state to the north. Almost all locations across California have recorded above-normal rainfall.

California’s snowpack continues its progression from pitiful in early January, to passable in early February, to plentiful by early March. For the first time since Oct. 1, most of the state’s mountains, with the possible exception of the Southern Sierra, could have a snow surplus by early next week.

Meanwhile, at some of the state’s reservoirs, which were above seasonal averages before the recent storms thanks to a wet winter last year, water is being released to avoid dangerously high levels in the coming weeks and months.

And the weeks ahead look favorable, even approaching ideal, for keeping the state flush with water with minimal flooding complications. 

“We should get a storm a week through March,” said Mike Anderson, California’s state climatologist. “It’s not shutting off. Hopefully, the pattern stays.”

Anderson, who works for the state’s Department of Water Resources, said besides adding precipitation, the coming pattern, with its lack of long stretches of sunny days, should help prevent rapid snow melt. These conditions would make it easier to capture and store runoff from the snowpack, which basically serves as a giant reservoir. 

The storm that started to pound the Sierra today has everything lined up perfectly for a very snowy few days, Anderson said. The storm, which originated in the Gulf of Alaska, has plenty of cold air and a long plume of moisture from the Pacific to tap into.

In dry years, storms of this magnitude avoid the state entirely, Anderson said.

“It’s a big storm,” he said. “We would normally expect something like this to show up most years. But we usually get it in January or February, not in March.”

Daniel Swain, a meteorologist and climatologist at UCLA, said the storm will bring extremely heavy snowfall rates – as much as 5 inches per hour in some spots. Some 24-hour and 48-hour snowfall records could be in jeopardy, including at lower elevations, which have seen very little snow so far this year because the storms have been relatively warm.

“Widespread 80- to 90-inch accumulations are possible at higher elevations,” Swain said. “And that’s probably a conservative estimate.” 

The heavy snow will coincide with winds gusting to 65 mph or greater, creating legitimate blizzard conditions starting tonight. It’s rare that the strongest winds and heaviest snow occur simultaneously, Swain said.

Different Down South

Big storms, common in late January and early February, have stopped showing up with regularity in San Diego. Ivory Small, science and operations officer at the National Weather Service’s Rancho Bernardo office, says since early February, the storm track has shifted north. The storm this weekend is tiny locally, but there is still plenty of potential out in the Pacific, and a shift back to the south in March would not be a big surprise.

On Feb. 2, the jet stream, the high-altitude winds that direct most storms around the globe from west to east, was extremely powerful and right over San Diego. Small said the winds above Miramar were clocked at 197 mph, the fastest he could recall in the region in decades.

“That was unusual – very unusual,” Small said. “What was happening early in the month, the lows were dropping farther south and more toward our coast. Lately, the lows have been progressing north.”

The supercharged jet stream in early February, Small said, was reminiscent of the conditions in 1997 – another El Niño year.

Dan Cayan, a climate researcher at the Scripps Institution of Oceanography, said an amplified jet stream is one of El Niño’s calling cards. Unlike other recent El Niños that fizzled and didn’t produce anticipated copious rainfall, he said this episode has more-or-less met expectations.

Along the California coast, as is often seen during significant El Niños, surface waters have been anomalously warm and sea levels have been anomalously high.

A deep, wintertime low-pressure system formed as expected in the North Pacific, Cayan said, albeit later than usual. It materialized the last half of January, which is when San Diego’s wet stretch began. 

“As typical of El Niño years, the subtropical Pacific jet stream was strongly activated,” Cayan said. “An associated (southerly) displaced and energetic storm track began to make landfall In California. In response to storminess, coastal ocean wave energy was … elevated, and with heightened sea levels, this caused some coastal damage.” 

Cayan said via email that El Niño is still in place, but it is starting to diminish. Accordingly, on-and-off North Pacific storminess affecting California may last through March, then fade.

“Most models predict El Niño will transition to neutral in late spring or early summer (May or June),” Cayan said. “Several models predict continued transition to La Niña conditions by late summer – autumn.”  

In the shorter term, the weather service’s Small said forecast models show another storm should visit San Diego County the middle of next week. He said he would not be surprised to see a strong jet stream return to Southern California in March, although probably not with the ferocity it displayed earlier this month.

“I would let people know that there’s still a lot of energy in the Pacific,” he said. “So keep those umbrellas handy.”

Rains we’ve had so far, Small said, have largely been beneficial. California’s fire season has been delayed, while at the same time, an estimated 1 million acres have burned this week in the Texas Panhandle and the southern Plains. 

“That’s what WE could be doing right now without this rain,” Small said. “This is a real plus, if you’re trying to keep your fire starts down. The moral of the story is, not too shabby.”

February Numbers

San Diego’s 4.58 inches of rain in February is more than double the monthly average (2.20). It is the city’s wettest February since 2005, when 5.83 inches were recorded. The city’s total for the season, which began Oct. 1, is 9.64 inches. Normal for the entire year is 9.79.

February in San Diego should end with an average temperature of 57.9 degrees, which is 1.1 degrees cooler than normal. 

Oceanside, which recorded 6.84 inches of rain in February, also more than doubled its normal rain for the month (2.90). But Oceanside has been more than 1.5 degrees warmer than normal.