'Historically Strong' El Niño, Extreme Winter Possible In CA

CALIFORNIA — The Golden State could see another winter for the record books if El Niño continues gaining steam and sticks around as long as forecasters expect. The National Oceanic and Atmospheric Administration updated its El Niño outlook late last week, one month after scientists confirmed the weather phenomenon's unusually early arrival.

Forecasters note the pattern almost always reaches peak strength between November and January, and on Thursday said there was an 81 percent chance El Niño would reach "moderate-to-strong" intensity during that timeframe.

There is also a 1 in 5 chance it could be "historically strong," rivaling the winters of 1997-98 and 2015-16, according to the updated advisory.

El Niño — the warmer phase of the El Niño Southern Oscillation (ENSO) — replaces its counterpart La Niña, which had stuck around for three consecutive winters. The opposing climate patterns are a departure from normal conditions in the Pacific and can have global impacts on the jet stream and weather, particularly during the winter months in the United States.

On Thursday, NOAA's Climate Prediction Center said the odds were greater than 90 percent that El Niño would persist through the 2023-24 winter season.

According to NOAA, El Niño causes the Pacific jet stream to shift south and spread east, which is usually associated with warmer and drier winter conditions in northern states and wetter conditions in the South and Southwest, including much of California.

No two El Niños are the same and a variety of factors can play into their overall influence, including how much strength it develops.

"El Niño can affect our weather significantly," NOAA explains. "The warmer waters cause the Pacific jet stream to move south of its neutral position. With this shift, areas in the northern U.S. and Canada are drier and warmer than usual. But in the U.S. Gulf Coast and Southeast, these periods are wetter than usual and have increased flooding."

The atmospheric response to El Niño can vary significantly, and impacts can be muddled when ocean temperatures are running warmer globally, as they are now. ENSO forecasters noted temperatures in the Pacific are notably above-average.

"In fact, the temperature of the subsurface in June 2023 was the third-warmest June value on our record, which goes back to 1979," wrote Emily Becker, the lead writer for NOAA's ENSO Blog. "This warm subsurface will feed the surface for the next few months, helping to sustain El Niño."

While much warmer temperatures in the Pacific are usually a strong indicator, the more widespread warmth lends to plenty of uncertainty.

"Generally, the stronger the sea surface temperature anomaly, the stronger the atmospheric response, and the more consistent the pattern of El Niño's remote impacts on rain and temperature patterns," Becker wrote. "However ... the warm global ocean may complicate this relationship."

ENSO forecasters update their El Niño outlooks every month, and NOAA typically releases its official U.S. Winter Outlook in October.