Oct. 20 (Bloomberg) -- The northern U.S. will be colder and wetter than normal in the coming winter as the drought in the South hangs on and probably spreads to Florida, according to the National Oceanic and Atmospheric Administration.
A cooling in the Pacific Ocean known as La Nina will drive much of the weather throughout the U.S., Mike Halpert, deputy director of NOAA’s Climate Prediction Center, said on a conference call today. The phenomenon tends to lead to a cooler, wetter North and a warmer, drier South.
The U.S. Northeast may also receive more snow than normal from December to February, Halpert said. Forecasts can’t be made with confidence for that region because of another weather pattern known as the Arctic Oscillation, which has a much greater impact on how much snow falls.
“Big snows in the East are often times related to the Arctic Oscillation and we don’t have the ability to forecast that much more than a week or two in advance,” said Halpert, who is based in Camp Springs, Maryland.
This will be the second year in a row La Nina has dominated weather across the U.S. The phenomenon is blamed for the widespread drought across the South that contributed to wildfires over 3.5 million acres and caused about $5 billion in agricultural losses in Texas, said David Brown, director of NOAA’s Southern Region Climate Services.
Parts of southeastern Texas need 30 inches of rain to return to normal moisture levels, and a large part of the state only received 5 percent to 10 percent of its normal precipitation in the last year, he said on the conference call.
Currently, 91 percent of Texas, 87 percent of Oklahoma and 63 percent of New Mexico have either extreme or exceptional drought conditions, the two most severe levels, Brown said. The La Nina-influenced winter season is expected to spread the drought throughout the southern U.S. into Florida.
Florida is the world’s second-largest citrus producer behind Brazil.
“Odds favor drier-than-normal conditions to continue this winter,” said Brown, who is based in Fort Worth, Texas. “Certainly La Nina is the most reliable predictor.”
In addition to drought in the South, Halpert said the most likely scenario for the coming winter is for the northern U.S. from the Pacific Northwest to the Great Lakes to be colder and wetter than normal.
The northern Great Plains and Ohio and Tennessee valleys will also have an increased chance of flooding, according to a NOAA statement. Earlier this year, heavy snows and rains caused record flooding on the Mississippi, Missouri and Ohio rivers.
Halpert said the Arctic Oscillation is like a see-saw of high and low pressure over the North Pole and the temperate regions to its south.
When the oscillation is positive, colder air stays over the pole, and when it is negative the frigid air drops down over temperate regions including the U.S.
The exact cause of the pressure flip-flop isn’t known and it’s hard to predict, he said.
“Sitting here in October, there is really no way to say what is going to happen in December and the rest of the winter,” Halpert said.
--Editors: Charlotte Porter, Dan Stets
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