El Niño update for California: Meteorologists say this one could be ‘historically strong’
Past El Niño years won’t help meteorologists determine what this winter will look like, the National Weather Service said in a Tuesday morning update, because conditions this year are not typical.
An El Niño was declared in May, meaning sea surface temperatures are warmer than normal in the equatorial eastern Pacific.
This region of the ocean typically drives large-scale atmospheric patterns that impact us locally, said Courtney Carpenter, warning coordination meteorologist with the National Weather Service in Sacramento, in a video update.
Here’s what El Niño conditions mean for California, and what meteorologists predict winter in the northern parts of the state will be like, as of late November:
How El Niño affects Northern California
Southern California and the desert southwest tend to be wetter than normal, and the Pacific northwest typically is warmer and dryer than normal in periods of El Niño, Carpenter said.
“As always, here in Northern California, we’re stuck somewhere in the middle,” she said.
In the past, Northern California has recorded anywhere from very dry to very wet winters during El Niño periods. Conditions in this part of the state typically lean toward wet or near normal, Carpenter said, but the region has seen some very dry El Niño winters.
Above normal snowfall during moderate and strong El Niño winters is typical at higher elevations, she said.
How strong will this year’s El Niño be?
This year, El Niño conditions developed earlier in the summer than previous ones have, Carpenter said.
“Typically, El Niño develops later in the fall into the winter,” she said. “This one was well in place here as we head into our winter.”
The probability of El Niño lasting through winter is 100%, Carpenter said. The conditions are anticipated to last through spring, with a 62% chance conditions will last through April to June 2024.
As it stands now, the probability of a strong El Niño in California is 75 to 85%, she said, with an over 35% probability of a “historically strong” El Niño that rivals 1997-98 and 2015-16.
A strong El Niño records surface water temperatures warmer than normal, the weather service said. The further the sea surface temperatures are away from normal, the stronger the El Niño event is said to be.
“(It’s) a mixed bag when we talk about El Niño and what that means for our winter,” Carpenter said.
Past vs. present El Niños in California
The El Niño that occurred in 1997-1998 recorded well-above-normal levels of precipitation, while 2015-2016’s El Niño was dryer than normal in most parts of the state.
“No two El Niño events are the same,” Carpenter said. “Even strong ones.”
Over the last several decades, the warmest region of the ocean has been the central Pacific, she said. This El Niño is notably warm in the eastern Pacific, off the coast of South America.
“We talk a lot about these extreme events occurring, but we’ve never really seen ocean temperatures this warm,” Carpenter said. “How that affects our storm pattern here locally remains to be seen.”
All of these factors mean meteorologists are going to be less reliant on past El Niño years to tell them what’s going to happen this winter, she said.
National Weather Service predicts winter outlook
Seasonal outlooks don’t capture how much it will or won’t rain, Carpenter said, but look at the overall pattern for a long period of time.
The odds are leaning toward above-normal precipitation for most of Northern California, Carpenter said. The Central Coast and Southern California are also in for a potentially wetter-than-normal year.
Temperatures are also predicted to be higher than normal across the state.
“Typically in El Niño winters, you see those warmer temperatures,” she said. “Warmer, wetter storms with higher snow levels.”
California typically sees five strong atmospheric rivers a year, with the exception of last year when the state saw double that amount, Carpenter said. California experienced over 20 atmospheric rivers in total in 2022.
The state is starting the season in a much different situation than it did last year after four years of exceptional drought, she said. This year, California had a very wet previous winter and a long-lasting snow pack, and the reservoirs are starting out much fuller than they were last winter.
“Any single storm can produce impacts — as we know — from strong winds, heavy snow and flooding either at the local scale or across the state.”
This story was originally published November 23, 2023 at 5:00 AM.
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