LOS ANGELES — On the heels of a record-setting wet and warm August, forecasters on Thursday announced that El Niño is gaining strength and will almost certainly persist into 2024.
El Niño, the warm phase of the El Niño-La Niña Southern Oscillation pattern, is a major driver of weather worldwide and is often associated with hotter global temperatures and wetter conditions in California.
The system arrived in June and has been steadily gaining strength, with a 95 percent chance that it will persist into at least the first three months of 2024, according to the National Oceanic and Atmospheric Administration. The odds of the system becoming a “strong” El Niño have increased to 71 percent.
That could result in a soggy January, February and March in Central and Southern California, said Daniel Swain, a climate scientist with UCLA.
“Right now, if you had to put money on it, the good money would probably be on a significantly wetter-than-average second half to winter in particular,” Swain said during a briefing Thursday, noting that those months are already the wettest time of year in Central and Southern California.
However, the odds of that occurring currently range from 40 percent to 60 percent, he said, so it is far from a guarantee.
NOAA officials shared a similarly inconclusive outlook for the Golden State. The strong El Niño will be meeting with long-term drying trends and anomalously warm ocean temperatures driven by climate change, making its outcome increasingly difficult to predict.
Forecasts currently show equal chances of wetter- or drier-than-normal conditions between October and December in most of California, said Scott Handel, a meteorologist with NOAA’s Climate Prediction Center.
But “given the strong El Niño event likely to occur this winter, we are leaning toward above-normal precipitation, slightly, for the Los Angeles area this winter,” he said.
Adding to the uncertainty is characteristic variation of El Niño events, with no two playing out the same way.
“It is never a guarantee,” said Jan Null, a meteorologist with Golden Gate Weather Services. “The best case study is last year with a La Niña, and all the models calling for below-normal precipitation. That was not what happened.”
This La Niña winter was among the wettest in recent memory, with more than 30 atmospheric rivers pummeling California, causing devastating levee breaches, fatal flooding and the resurgence of Tulare Lake.
Null said data from previous El Niño events also demonstrate its unpredictability. A strong El Niño in 1957-58 resulted in above-average precipitation across California, as did very strong El Niños in 1982-83 and 1997-98.
But the most recent very strong El Niño in 2015-16 was relatively dry in California, resulting in just 86 percent of normal precipitation in the South Coast region that includes Los Angeles, Null said.
“I would not put any money on a long-range forecast — there are too many other things that could change the outcome,” he said.
That includes lesser-known patterns that can also affect weather behavior, such as the Madden-Julian Oscillation, the Pacific Decadal Oscillation and the North Atlantic Oscillation.
Null said most of the models he has reviewed point to a “dry-ish” December, a “normal-ish” January, and a February and March that are above normal for precipitation.
“All of this is overlaid with the fact that the oceans and the atmosphere are warmer,” he added. “Every weather event has some climate change DNA in it these days.”
Indeed, the outlook comes as NOAA officials affirm that August was Earth’s hottest month on record. The three-month period of June through August, known as meteorological summer in the Northern Hemisphere, saw record warmth as well.