Water & Drought

Forecasters see 95% chance of El Niño this winter

From left, Dominic Smith, Aiden Shephard  and Blake Machado,  all age 14 and of El Dorado Hills, wade to shore around rocks exposed by the American River’s low water level near the Rainbow Bridge in Folsom earlier this summer.
From left, Dominic Smith, Aiden Shephard and Blake Machado, all age 14 and of El Dorado Hills, wade to shore around rocks exposed by the American River’s low water level near the Rainbow Bridge in Folsom earlier this summer. pkitagaki@sacbee.com

As Sacramentans endured another round of triple-digit temperatures Thursday, weather forecasters offered predictions of relief in the months to come: A strong El Niño winter is almost certainly heading toward California, likely bringing heavy precipitation.

The National Weather Service’s Climate Prediction Center, in its monthly update, said California has a 95 percent chance of experiencing El Niño this winter. That’s up from 90 percent a month ago and 85 percent in June.

“The news is that ... we now have a strong El Niño,” said Mike Halpert, deputy director of the climate center in College Park, Md., during a conference call with reporters. “Obviously, our confidence is increasing.”

Forecasters said El Niño is shaping up as one of the fiercest on record, possibly in the top three. But they said it’s unlikely to be as strong as the winter of 1997-98, when the Sacramento region was drenched with rains and deadly floods hit portions of the Sacramento Valley.

And there probably won’t be enough precipitation to cure the drought, forecasters warned. The Sierra Nevada needs three times the normal precipitation to wipe out the state’s water shortage. The wettest winter on record, in 1982-83, was just twice as wet as normal, said Kevin Werner, director of the National Oceanic and Atmospheric Administration’s regional climate service in Seattle.

“One season of above-normal rain and snow is unlikely to erase four years of drought,” Halpert said.

On a day when temperatures hit 107 degrees in Sacramento, state officials were quick to warn that Californians shouldn’t assume the drought is ending. State residents reduced water consumption by 31 percent in July, significantly above Gov. Jerry Brown’s executive order calling for 25 percent savings, and officials don’t want Californians to become complacent.

“Current El Niño conditions cannot tell us how many storms may cross California this coming winter or how much rain and snow will fall in our state,” said state climatologist Michael Anderson in a prepared statement. “Strong El Niño events in the past have led to wetter-than-average conditions in the southern part of the state but offered mixed results for California’s main water supply regions in the north. This uncertainty means that Californians should continue to use water carefully and sparingly in the face of the ongoing extreme drought.”

El Niño is a fairly reliable predictor of rains in Central and Southern California. But Werner said “there are weak correlations” between the El Niño phenomenon and what happens in Northern California, home to the state’s two most important reservoirs, Shasta and Oroville.

Nor could forecasters say if the precipitation in Northern California will fall as rain or snow. Water officials prefer a bountiful snowpack, which is easier and more predictable to manage.

One season of above-normal rain and snow is unlikely to erase four years of drought.

Mike Halpert, Climate Prediction Center

“There’s a lot of uncertainty,” Werner said.

El Niño winters generally occur when equatorial Pacific Ocean temperatures rise at least 1.5 degrees Celsius above normal during the preceding summer. In August, temperatures were 2 degrees Celsius, or 3.6 degrees Fahrenheit, above normal.

The temperature differential isn’t as pronounced as it was in the months leading up to the 1997-98 El Niño winter. And the wind patterns suggest that a repeat of 1997-98 isn’t likely.

The 1997 pattern “by any measure ... is still stronger than 2015,” Halpert said.

The forecasters also cautioned that El Niño doesn’t guarantee a wet winter. The summer of 1987 saw one of the strongest El Niño patterns ever, but the ensuing winter was something of a dud: just 15 inches of rain in Sacramento, about 3 inches less than normal.

El Niño patterns bring different weather to different parts of the country. Halpert said the Pacific Northwest is likely to experience “drier than average conditions” this winter. He added that El Niño has already made for a relatively quiet hurricane season in the Southeast.

Dale Kasler: 916-321-1066, @dakasler

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