Dry winter on tap — or not: Forecast finds a fickle finger
The coming winter is likely to be dry in California, and drought conditions may begin to emerge in the central part of the state, federal climate experts warned Thursday.
But forecasters with the National Oceanic and Atmospheric Administration also said weather patterns are fickle this year, and there’s no clear sign that another prolonged drought like the one that squeezed California earlier this decade will settle in.
“It’s something to keep an eye out on and see how the winter progresses,” said David Miskus, a meteorologist at NOAA’s Climate Prediction Center in College Park, Md. “By February and March, it might become wet again.”
The longterm forecast for California is part of the federal government’s “201920 Winter Outlook.” As with California,
the annual report remained somewhat tentative with its projections for most of the country, largely because telltale weather patterns like El Niño are absent from the picture this year.
Without a dominant atmospheric driver, forecasters anticipate wide swings in temperature and rainfall from December to February, not unlike what the folksy Farmers’ Almanac predicted this year when it called for a Polar Coaster.
Still, federal scientists believe that most states, including California, will be warmer than average this winter. No state is projected to have lowerthanaverage temperatures.
Precipitation will be more variable, they say. Higher levels of rainfall are more likely in the northern tier of the continental U.S., Hawaii and Alaska, while lower levels of rain are more likely along the western part of the Gulf of Mexico as well as in Northern and Central California.
Without an El Niño or a La Niña pattern over the Pacific Ocean, meaning no significant anomalies in tropical sea surface temperatures, the forecasters fell back on lesspredictive weather phenomena, including the MaddenJulian Oscillation and the Arctic Oscillation. These more intermittent and roving atmospheric patterns can whip up winds and clouds in certain parts of the globe — or not — depending on their position.
Such influences favor warm, dry weather along the West Coast in the coming months, according to the outlook, though there’s no evidence such conditions will persist.
A warm patch of water in the northeastern Pacific, sometimes called the Blob, could also contribute to higher temperatures and less rain in California, though that effect is likely to be minimal and shortlived as well, according to the outlook.
Many forecasters outside the Climate Prediction Center downplayed the utility of the government’s outlook, citing the difficulty of making longterm projections.
“They were predicting dry weather for California the last two years,” said Bryan Allegretto, cofounder of the popular forecasting website OpenSnow.com, noting that the federal outlook fell short both times. “A shortrange oscillation can change the entire season in three weeks.”
While past winters started dry, Allegretto said, lateseason fronts quickly turned them around. Last winter, a record wet February brought the seasonal snowpack in the Sierra to a whopping 202% of average.
The Climate Prediction Center acknowledges its outlooks have shortfalls, though it cites a track record of being right more often than being wrong.
The federal government’s report does not include projections for snowfall, partly because it’s difficult to predict. Allegretto, who’s not a meteorologist but is known for his accurate longrange snow forecasts, said he wasn’t about to hazard a guess this early in the season.
Because some recent winters have been wet and California’s big reservoirs are fuller than average, prophesies of a dry year ahead are not as worrisome, though the question of snow remains germane.
Sierra snow is critical to the state’s water supply. Even after a wet winter season ends, melting snow continues to fill reservoirs, providing a boost that cities and farms have come to rely on. The warming climate, however, has meant less snow in recent decades.
“We’re seeing an everincreasing fraction of our precipitation as rain,” said Randall Osterhuber, a snow hydrologist at the UC Berkeley Central Sierra Snow Laboratory in Soda Springs (Nevada County).
Osterhuber said the changing balance of rain and snow has important implications for California’s future water picture, but the trend has little use in yeartoyear forecasting.
“This does not mean that next year is going to be rainier than last year,” he said. “Ask me in May, and I’ll tell you all about this winter.”