A new U.S. government forecast predicts that much of the southern United States will receive above-average precipitation this winter, while northern parts of the country could experience a drier-than-normal season. Credit: NOAA

This winter could bring some desperately needed rainfall to parched California, the Southwest, and other water-starved regions but worsen drought or lead to drier-than-usual conditions in some other large swaths of the country, the U.S. government’s premiere civilian weather and climate monitoring agency announced Thursday. The periodic climate pattern called El Niño, which promises to be exceptionally intense in coming months, dominates the just-released December 2015 to February 2016 weather outlook from the National Oceanic and Atmospheric Administration (NOAA).

El Niño is a warming of the eastern equatorial Pacific Ocean that recurs every 2 to 7 years and roils rainfall and temperature patterns worldwide. NOAA forecasters have previously reported that the current El Niño could develop into one of the three strongest since 1950.

Because El Niños can sometimes bring increased rain to California, this winter’s NOAA outlook sees some drought relief in southern and central parts of the state. Additional statewide drought relief might occur during February and March, the outlook suggests.

Although the winter outlook is good news for California, a wet winter is not guaranteed.

“Although the winter outlook is good news for California, a wet winter is not guaranteed, and even a wetter-than-average winter is unlikely to erase 4 years of drought,” said Mike Halpert, deputy director of NOAA’s Climate Prediction Center in College Park, Md., in a conference call for reporters on Thursday.

In a NOAA press release issued the same day as the press briefing, Halpert stated, “California would need close to twice its normal rainfall to get out of drought, and that’s unlikely.”

No Cure-All

El Niño does not provide a drought cure-all for a couple of reasons. First, El Niño wields limited influence on the complex global climate system of which it’s a part. Second, El Niño typically delivers uneven amounts of rain across California.

NOAA assigns a probability of occurrence to each of its predictions, indicating the odds that an anticipated weather pattern will actually occur. Southern California is looking at a 50% chance of experiencing a wetter-than-normal winter, according to the agency. However, NOAA expects only a 33% chance of a wetter winter in Northern California.

“[El Niño] really offers less predictability for a wetter-than-normal winter in Northern California—a region where it could have the greatest impact on lessening the drought,” Alan Haynes, NOAA’s service coordination hydrologist in the California Nevada River Forecast Center in Sacramento, Calif., told reporters in the press teleconference. Much of California’s annual water supply accumulates in reservoirs and snowpacks in the state’s north.

The winter weather outlook forecasts a wetter winter than usual for the Southwest, South, and mid-Atlantic. In Florida, the chance of soggier conditions reaches 70%. The Southern Plains region and the South are also headed for a colder-than-normal winter, according to the forecast.

High and Dry

El Niño could very well exacerbate an emerging drought in the Pacific Northwest.

While El Niño might provide some drought relief to parts of California and drought-plagued southern regions, it could very well exacerbate an emerging drought in the Pacific Northwest—which is forecast to have a warmer winter than usual.

“El Niño increases the chances for drier and warmer weather in the Pacific Northwest, where drought has started to develop,” said Haynes. What’s more, “below-median precipitation is most likely” for the region, according to the winter outlook.

Drought development is also “likely in Hawaii, parts of the northern Great Plains, and in the northern Great Lakes region,” said Halpert. The outlook foresees a drier-than-usual winter in western Alaska and the northern Rocky Mountains as well. Unusual warmth will prevail in Hawaii, Alaska, the West Coast, northern Great Plains, Great Lake regions, and Northeast, with probabilities ranging from 33% up to 60%, according to NOAA.

Past El Niños coincided with outbreaks of winter tornadoes in the Southeast and Florida. This winter will also bring an elevated risk of tornadoes, according to Halpert.

—Cody Sullivan, Writer Intern

Citation: Sullivan, C. (2015), This winter’s El Niño might only dent western U.S. drought, Eos, 96, doi:10.1029/2015EO037601. Published on 16 October 2015.

Text © 2015. The authors. CC BY-NC 3.0
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