The likelihood of a potentially powerful El Nino taking shape in the Pacific Ocean is increasing, raising concerns that Southern California could be hit with a season of extreme rainfall.
There is now an 82% chance that El Nino is likely to emerge in the next few months, up from the 61% chance estimated a month ago. And now it has a 96% chance climate patterns The National Weather Service’s Climate Prediction Center said Thursday that the phenomenon — characterized by warm ocean waters in the central and eastern tropical Pacific — will remain in place this winter.
It remains to be seen how strong this recurrence of El Nino could be. There is up to a 37% chance that this will happen “very strongby the end of the year, exceeding the forecast of 25% issued last month.
Forecasters also said there was a 30% chance that El Nino would be “strong”, a 22% chance it would be “moderate” and a 9% chance it would be “weak”.
According to Marty Ralph, director of the Center for Western Weather and Water Extremes at the Scripps Institution of Oceanography at UC San Diego, many forecast models suggest “a very large El Niño” will occur.
“There’s a pretty good chance that it’s well above the El Nino threshold, in a modest way, and then there’s some chance that it’s well above that,” he said earlier this week.
(Paul Duginsky/Los Angeles Times)
Just three weeks ago, the World Meteorological Organization said it had observed a marked change in sea surface temperatures in the equatorial Pacific, a sign that the arrival of El Niño is imminent.
“There is high confidence in the onset of El Niño, which will then intensify in the coming months,” Wilfran Moufouma-Oukia, the organization’s climate forecasting chief, said in a statement. statement. “Models indicate this could be a strong event.”
However, he said forecasts are evolving and may still change. But Thursday’s announcement indicates that the likelihood of a powerful El Niño continues to increase.
According to WMO, El Niño is one of the most powerful climate patterns on Earth, capable of reshaping global weather and influencing rainfall and drought. It usually occurs every two to seven years and lasts about nine to 12 months.
According to the National Weather Service, a typical El Niño is associated with above-average rainfall in Southern California. A strong El Niño could shift a subtropical jet stream that normally brings rain to the forests of southern Mexico and Central America toward California and the southern United States.
Although there’s no doubt that El Niño will bring a powerful rainy season to Southern California, some of the earlier high-powered patterns have been monsters.
There have been only three “very strong” El Niños in the past half century, in 1982–83, 1997–98 and 2015–16. The first two brought heavy and destructive amounts of rainfall to the Golden State.
In early 1998, the storm caused massive flooding and landslides in California, killing 17 people and causing more than half a billion dollars in damage. Nearly a year’s worth of rain fell on Downtown LA in just one month. At least 27 homes were so severely damaged that they could not be safely placed along the coast, according to California Coastal Commission.
During the winter of 1982–83, damage on the coast was particularly severe due to high tides amid powerful storms. Approximately $100 million in damage was reported. US Army Corps of Engineers informed 33 seaside homes were destroyed and another 3,000 homes, as well as 900 coastal businesses, were damaged by storm surge, waves, erosion, and other forces.
But 2015–16 El Nino – despite being strong in the equatorial Pacific – did not bring the expected rainfall impact to Southern California, and failed to pull the state out of a five-year drought. That water year actually saw below average rainfall in the region, and average or above average rainfall in Northern California.
However, according to the Coastal Commission El Niño “caused record coastal erosion on many California beaches.”
The effects of that season’s El Niño were more consequential elsewhere. The central North Pacific had a “record-breaking hurricane season” with 16 tropical cyclones moving through the unusually warm ocean – more than three times the average, according to National Oceanic and Atmospheric Administration. Severe drought also occurred in the Caribbean – so severe that 65% of Antigua’s farmers went out of business, with a 1 billion gallon reservoir dried up.
Therein lies a big asterisk regarding El Nino. Since 2000 or so, Ralph said, “The traditionally expected relationship between El Niño, La Niña, Southern California, and winter wetness has gone the other way. El Niño has not been excessively wet, and La Niña has been extra wet.”
During La Niña, sea surface temperatures in the central and eastern Pacific Ocean cool – the opposite of the El Niño trend. The jet stream also shifts northward, typically pushing winter storms toward the Pacific Northwest and Canada, while parts of California become drier than average, especially in the south.
Ralph co-authored a scientific paper that specifically sought to understand why 2010–11, 2016–17, and 2022–23 were very wet years in California despite the existence of La Niña. As it turns out, El Nino and La Nina aren’t the only players in determining how much rain and snowfall Southern California gets.
The El Nino/La Nina pattern likely affects some storms that hit California, Ralph said, but only the typical seasonal variations that originate north of Alaska or Hawaii. El Niño and its cold sister pattern, however, do not affect the “atmospheric rivers” that can bring large amounts of precipitation from tropical regions to California, Ralph said.
These types of storms have become increasingly prevalent in recent years, leading to powerful winter storms even without the presence of El Niño.
For example, last fall brought with it another La Niña, and a dangerously dry winter was expected for Southern California. Instead, the weather was wetter than average. .
But the 2023–24 El Niño, known as “strong”, brought with it a significantly wetter year for Southern California, with Downtown LA receiving 155% of normal annual rainfall. That February, record rainfall occurred and a memorable five days of continuous rain occurred, causing hundreds of landslides in LA alone. Dozens of homes and buildings were damaged by the debris flow, including 15 houses that were red tagged.
While El Niño doesn’t always perform as expected for Southern California, some experts still find value in using its arrival as a scene-setter for potential weather impacts. According to the World Meteorological Organization and the National Weather Service, El Niño is usually associated with increased rainfall over parts of southern South America, Central Asia, and the Horn of Africa. is also associated with dry season in Washington, Oregon, Idaho and Alaska, as well ohio river valley in the Midwest and upper South, as well as Australia, Indonesia, and parts of southern Asia.
If a strong El Nino arrives, it could tag the team along with the existing deep marine heat wave on the West Coast. Both the marine heat wave and the coming El Niño “will have impacts on animals, fish, birds and marine mammals,” said Andrew Leasing, a research oceanographer at NOAA’s Southwest Fisheries Science Center.
“In general, warmer water – whether it’s a marine heat wave or El Niño – reduces ecosystem productivity at the base of the food web, and thus there is less food around and up the food chain for our larger animals, fish, birds, etc.,” Leising said.
Leising said he expects the current marine heat wave, which would normally begin to subside between October and December, to become longer due to the arrival of warm sea water from El Niño.
He doesn’t expect we’ll see “extremely hot temperatures” with the confluence of a marine heat wave and El Niño, “but I wouldn’t be surprised if we break some records this fall, even if by small margins.”
Scientists don’t know much about the cumulative effects of a long-lasting marine heat wave. One effect is that, according to Leesing, they “keep prey around them in deeper water”, as they don’t like really warm water near the surface.
“Let’s say we keep this heat away from SoCal, and it turns into heat coming from El Nino during the fall and winter. It will take a longer time for animals to be exposed to these warmer temperatures, so not only will they have less food, but the warmer temperatures alone could be a problem for some of them,” he said.
The current marine heat wave technically began in May 2025, waning as last expected, but then did not retreat from the coast and stayed away from Southern California, Leising said.
“Then it expanded again during December and basically it’s continued ever since, and is stuck there near Southern California. That’s not a normal pattern.”
