El Niño conditions present, rain or snow a maybe

By JP Crumrine
Correspondent

Before the forecast, just a recognition that it was warm, actually very hot, on the Hill last week. The National Weather Service (NWS) reported that the temperature reached 88 degrees in Idyllwild Oct. 18. That is 3 degrees higher than the previous high of 85 degrees recorded in 2003. As this week cools, what is ahead?

Out of three possible precipitation outcomes for the coming winter — much wetter than average, much drier than average or near average — National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center’s outlook for December-February says that odds are leaning toward a much drier than average winter for northern states from the Great Lakes to eastern Washington and toward a much wetter than average winter across the South, with the highest odds of a relatively wet winter in the Southeast. White areas mean equal chances for all three possible outcomes. **NOAA CLIMATE PREDICTION CENTER MAP.**

Winter is approaching and what can meteorologists tell us?

That cooler, lower temperatures are coming and an El Niño condition is present along the equatorial Pacific Ocean.

And for precipitation?

“There’s a high uncertainty for the precipitation forecast for 2023-24,” said Alex Tardy, warning coordination meteorologist at the NWS San Diego office.

Even the NWS winter forecast released last week said the odds of a wetter than average winter in Southern California were only 30 to 40%. That follows their forecast earlier this month that there was a 75 to 85% chance of a “strong” El Niño during November through January and a 30% chance of a “historically strong” El Niño.

El Niños have typically brought wetter winters to the Hill. But that has not always been the case during the past 30 years. Although the winter of 1997-98 was very snowy, recent El Niños, except for 2016, have been drier than average.

Last winter’s precipitation occurred in the third year of La Niña conditions, which are more typically dry.

Daniel Swain, climate scientist at the Institute of the Environment and Sustainability at the University of California, Los Angeles, said current conditions should tilt the odds toward a wetter than average winter in Southern California, but the very warm ocean temperatures in the northern Pacific are a new twist. These could affect the routes of the jet stream that complicates long-term forecasts.

“Short-term forecasts are much better than seasonal because the models don’t care about the ocean temps for the next few days,” he said last week on his monthly YouTube video. “There is more uncertainty than usual for an El Niño of this size.”

But the NWS outlook for December through January predicts chances of precipitation exceeding averages in Southern California by only 30 to 40%. Better than even odds, but not high.

“An enhanced southern jet stream and associated moisture often present during strong El Niño events supports high odds for above-average precipitation for the Gulf Coast, lower Mississippi Valley and Southeast states this winter,” said Jon Gottschalck, chief of the Operational Prediction Branch of the NWS Climate Prediction Center in an Oct. 18 news release. But note that he did not include Southern California in this statement.

However, if the jet stream does drop far enough south to drive atmospheric rivers across Southern California, this winter may rival 2022-23. Last year, Idyllwild received 45.5 inches of precipitation, almost double the long-term average of 24.4 inches. That was the fourth wettest winter in 80 years.

On Sunday, the NWS short-term forecast for the week was “Fair, dry, and seasonal weather should prevail over the mountains and deserts this week. Temperatures will be slightly below average through midweek, followed by modest warming later in the week.” But Swain said, “A stronger but mainly dry ‘inside slider’ low pressure system will move across Great Basin, bringing much colder/windier conditions in CA.”