La Niña Usually Equals A Dry Winter. So Why Is CA Getting So Much Rain?

In just a few days, a relentless stretch of storms tore across California, killing seven people, triggering evacuations and sending floodwater racing through burn scars.

The rapid-fire systems may have surprised residents anticipating a drier winter, but a National Weather Service meteorologist told Patch a weak phase like La Niña can still deliver a few surprises.

Brian Lewis, a meteorologist with the National Weather Service’s Oxnard office, said forecasters rely heavily on guidance from NOAA’s Climate Prediction Center when interpreting the El Niño-Southern Oscillation, or ENSO. This climate phenomenon can offer hints of how seasons may pan out, but it can't tell a complete story.

Most Californians understand that El Niño equals a wet winter and La Niña equals a dry one. But Lewis says that the rule of thumb doesn't always work.

The recent storms illustrate how other climate factors can override the typical influence of La Niña, especially when ocean temperatures elsewhere in the Pacific run unusually warm, he said.

“There’s even some interpretation that the warmer Pacific is kind of overriding some of those colder equator temperatures,” Lewis told Patch.

That warmer backdrop, he noted, may be helping fuel the steady stream of storms that has moved across the region this month.

Seasonal outlooks heading into winter favored below-normal rainfall and warmer-than-average temperatures across much of California, Lewis said. But the recent stretch of storms, including several that broke daily or monthly rainfall records across Southern California, has complicated those early projections.

“One storm can really change things quite a bit, especially when we have an atmosphere where it really gets picked up by a storm system coming south,” he said.

New data from the NWS confirmed just how historic the latest storm was for Southern California.

With 6.01 inches of rain falling over three days, Santa Barbara marked its wettest three-day stretch ever recorded in November, surpassing a 2002 record. On Sunday alone, Santa Barbara Airport logged 2.90 inches, its third-wettest November day on record.

Also as of Sunday, Oxnard recorded 3.18 inches of rain — not only a new daily record, but also the third-wettest November day since records began in 1923.

Meanwhile, the Bay Area also saw unusual rainfall totals recorded on Monday. San Francisco International Airport recorded 1.14 inches on Monday, breaking the previous daily record of 0.91 inches set in 1996, according to the weather service.

Looking ahead, Lewis said the rainstorms may briefly quiet down after this weekend, with projections showing a drier stretch before the possibility of another storm arriving in early December. But with a weak La Niña in place, he cautioned that the signal is not strong enough to offer a clear picture of how the rest of winter will unfold.

“With the weak La Niña, be prepared for anything,” Lewis said. “It’s not as strong of a signal as a strong El Niño, where the climatology is a little more obvious.”

He said some past La Niña years brought wet weather in October and November, followed by a sharp turn toward dry conditions for the rest of winter — another reminder that long-range forecasts can offer limited certainty for California.

Lewis said the recent storms were forecast by local offices, but compared with seasonal projections, they could be seen as unexpected.

“In terms of the outlook that was put out, yeah, I think that’s maybe fair just compared to climatology,” he said.

For now, he said, Californians should watch day-to-day forecasts and remain aware that short-term weather patterns can override seasonal expectations, especially when ENSO signals are weak.

Bay Area meteorologist Jan Null told the San Francisco Chronicle this week that when El Niño entered public consciousness in the early 1980s, it was when the state recorded one of the wettest winters on record.

“Then we hit 1997-98 — another huge El Niño, another flood season," Null said. "So that idea got cemented. Once it’s in the public psyche, it’s hard to shake.”