The National Ocean and Atmospheric Administration said in its US winter weather outlook that La Niña will make an appearance December through February for the third year in a row.
It’s not unusual to see two consecutive winters marked by La Niña, but what US forecasters are calling a “triple dip” is uncommon. Going back some 70 years, this has occurred only two other times.
“It has happened in the past, but it’s not normal,” said Brian Garcia, a meteorologist with the National Weather Service.
What does this mean for the water-starved San Francisco Bay Area? Last winter was abnormally dry amid a La Niña pattern. Could the region see the same this winter?
With La Niña persisting, NOAA’s winter forecast favors wetter weather in the Pacific Northwest and drier conditions in Southern California, for December 2022 to February 2023. Northern California and the Bay Area fall in an in-between area, where the odds of the winter going in one direction or the other aren’t strong. The outlook map suggests the likelihood of a warmer winter are slightly higher than a chillier one in the Bay Area, while there are equal chances of above average, below average and normal precipitation.
The rain forecast is the result of data from past winters marked by La Niña. While the Bay Area has seen more abnormally dry winters during La Niña years, it has also average years and unusually wet ones.
“The forecast of equal chances in your area does in fact mean that current climate signals and historical forecast reliability in your region don’t allow for a confident or reliable forecast shift in climatological probabilities,” Jon Gottschalk, chief of the NOAA Climate Prediction Center’s forecasting branch, wrote in an email. “So the odds at the current time for your area are 33% for each category. No clear shift either way unfortunately. Your area is notorious for high variability or outcomes during La Nina event winters and this is why equal chances is forecast.”
NOAA released its 2022-23 winter weather outlook.
NOAALa Niña is a weather phenomenon that occurs when the equatorial waters in the eastern and central Pacific Ocean cool to below-normal averages. The better-known El Niño, the inverse of La Niña, is when the waters warm. Both can impact the atmospheric conditions worldwide, including the jet stream and storm track.
Local meteorologist Jan Null of Golden Gate Weather Services said that while La Niña influences winter weather, many other factors are at play, including a smattering of oscillations, such as the Arctic and Magellan-Julian oscillations.
“El Niño and La Niña, they are the superstars of the team,” Null said. “They have the highest probability of having a big night. Some of these other bench players can come in and still influence the game.”
A big twists in this year’s forecast is that NOAA predicts La Niña will transition to what’s called ENSO neutral as early as February. In ENSO, the equatorial waters are at average temperatures. A similar pattern occurred in 2016-17, when winter started dry but had a wet ending.
“We had one or two storms in 2016 and then once we turned the new year and we popped out of La Niña, the storm completely blew open,” said Garcia, who works for the weather service’s Bay Area office. “We had two months of nonstop rain. It seemed like nonstop rain. We had so many atmospheric rivers come through our area. That was the year Coyote Creek flooded in San Jose.”
Garcia predicts that 2022-23 could unfold similarly.
“This winter, we will get rain,” he said. “The question is, ‘How much rain will we get?’ From things that I’ve been looking at, it looks like it’s going to be back-loaded. We’ll get a few fronts come through and give us a little bit of rain during the last part of this calendar year, but I really think the next calendar year is going to be the time when we get hit; probably late February through April is going to be our window this year. If we get something in March, we have ‘Miracle March.’ If we get something in April, we have our ‘Amazing April.'”
Null isn’t ready to make a prediction and is sticking with NOAA’s forecast that doesn’t favor one scenario over another.
“I think we just don’t know,” he said. “If somebody really had the answer, they’d be the richest person on the planet.”
This news story has been updated.