A pair of winter weather outlooks released last week by prominent forecasters call for colder weather across the Mid-Atlantic region in coming months, and each said the nation's winter weather will be significantly effected by the current El Nino event, though one outlook called for a fading El Nino and the other sees El Nino strengthening.
Below-average temperatures that will dominate the Mid-Atlantic and Southeast United States from December through February will be driven in large part by El Nino -- the warming of surface temperatures in the central and eastern equatorial Pacific Ocean, according to a winter weather outlook released Thursday by the National Oceanic and Atmospheric Administration (NOAA).
"We expect El Nino to strengthen and persist through the winter months, providing clues as to what the weather will be like during the period," said NOAA's Michael Halpert, deputy director of the Climate Prediction Center. "Warmer ocean water in the equatorial Pacific shifts the patterns of tropical rainfall that in turn change the strength and position of the jet stream and storms over the Pacific Ocean and the U.S."
Other factors, including the North Atlantic Oscillation, are difficult to predict more than one or two weeks in advance, adding uncertainty to forecasts for the Northeast and Mid-Atlantic portions of the country, Halpert added.
NOAA's winter outlook calls for below-average temperatures from southern and eastern Texas to southern Pennsylvania and south through Florida; warmer-than-average temperatures across much of the West and Central regions, especially in an area stretching from Montana to Wisconsin.
The forecast also predicts above-average precipitation in Texas, Florida and the southern portions of Louisiana, Mississippi, Alabama, Georgia and South Carolina. Drier-than-average conditions are expected in the Pacific Northwest and in the Ohio and Tennessee River valleys, NOAA said.
NOAA's winter forecast was similar to one issued a day earlier by AccuWeather.com Chief Long Range Forecaster Joe Bastardi, though Bastardi said he expects the current El Nino event to fade in coming months. The demise of El Nino will result in the stormiest and coldest winter weather pattern in recent years, with an area from southern New England through the Appalachians and Mid-Atlantic, including the Carolinas, being hit hardest, according to Bastardi.
The fading El Nino pattern "will lead to a stormier and colder winter in the southern and eastern United States...[and] other factors are pointing to a winter very similar to that of 2002-2003," Bastardi said.
The storm track that could develop this year will bring storms into Southern California, then across the South and up the eastern seaboard. New York, Boston and Philadelphia could all get up to 75% of their total snowfall in two or three big storms this winter, Bastardi said. Over the past two winters storms tended to take a track farther west from Texas into the Great Lakes, bringing unseasonably mild weather to major East Coast cities.
Areas from Atlanta to Charlotte could have several snowstorms this winter, while the Interstate 20 corridor from Dallas to Atlanta "will be a strike zone for ice and snow," Bastardi said.
The Midwest and central Plains could see below-normal snowfall and temperatures averaging a bit milder than in past years, while a warm and somewhat dry weather pattern is expected from the Pacific Northwest into the northern Plains, he said. The barrage of winter storms that typically hit the Northwest may not occur this winter, but could be seen south in Southern California and portions of the Southwest.
In July, Bastardi said cooler-than-normal summer weather in the Northeast might be a hint that a cold, snowy winter was in store for an area stretching from Boston to Washington, DC (see NGI, July 20). El Nino and recent worldwide volcanic activity may have played a role in the summer cooling trend, Bastardi said.
In a seasonal forecast issued last month, Andover, MA-based WSI Corp. said the final quarter of 2009 will bring cooler-than-normal temperatures to much of the Southeast and Central United States, but above-normal temperatures will dominate key Northeast heating markets for two of the three months (see NGI, Sept. 28). In contrast to Bastardi's forecast, WSI said a moderate El Nino event will probably continue through the winter.
The latest El Nino arrived at the end of June, according to National Oceanic and Atmospheric Administration (NOAA) scientists (see NGI, July 13). El Nino events, which occur every two to five years and typically last about 12 months, are believed to affect a variety of North American weather patterns.
Bastardi and other forecasters, including NOAA and WSI, have said the latest El Nino has played a part in creating a relatively quiet 2009 Atlantic hurricane season (see NGI, June 29).
A cold start to the winter season could snap natural gas storage inventories lower and send prices higher, but it will take a lot more to bring the overflowing storage situation back to a neutral level, Barclays Capital analysts said recently (see NGI, Oct. 12). Only a 10% colder-than-normal winter over the 30-year average, they said, would bring storage balances "back to still near-record levels of last year."
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