A weak El Nino under way in the Pacific Ocean should contribute to a mild winter for much of the United States, the National Weather Service reported Tuesday.
“The strengthening El Nino event will influence the position and strength of the jet stream over the Pacific Ocean, which in turn will affect winter precipitation and temperature patterns across the country,” Michael Halpert, lead forecaster at the NOAA Climate Prediction Center, said in a statement.
“This event is likely to result in fewer cold air outbreaks in the country than would be expected to occur in a typical non-El Nino winter,” Halpert said.
El Nino, a warming of the tropical Pacific sea surface, accompanied by changes in winds and air pressure, began in September and is expected to last into next year.
The result, forecasters said, should be a winter marked by above-normal temperatures, though perhaps not as mild as last year’s very warm winter.
Drought is expected to ease in most areas of the Southwest, though some drought is anticipated in parts of the Pacific Northwest.
While the El Nino could strengthen during the next few months, it is not expected to reach the magnitude of the very strong 1997-1998 El Nino.
According to the National Oceanic and Atmospheric Administration forecast for December through February, the 48 contiguous states can expect about two percent fewer heating degree days than average, but about five to 10 percent more heating degree days than last year’s very warm winter.
Fifth warmest on record
The winter of 2005-2006 was the fifth warmest on record for the United States with an average temperature of 36.29 degrees Fahrenheit — 1.2 degrees above normal — for the 48 contiguous states. The warmest winter on record was 1999-2000 at 36.95 degrees.
Heating degree days are used as a measure of how much heating fuel is needed. A degree day is measured for each degree Fahrenheit the average temperature of a place falls below 65. For example, if a town averages 63 one day, there were 2 heating degree days that day, if the average is 60 there are 5 degree days.
Expected to have warmer-than-normal winter temperatures are the West, Southwest, Plains states, Midwest, most of the Northeast and northern mid-Atlantic, as well as most of Alaska.
Readings are forecast to be close to normal for parts of the Southeast, while below-average temperatures are anticipated for Hawaii.
The outlook is for equal chances of warmer or cooler than normal for Maine, the southern mid-Atlantic, Tennessee Valley and much of Texas.
For rain and snowfall, the outlook is for wetter-than-average conditions across the Southwest from Southern California to Texas, and for Florida and the south Atlantic Coast.
Drier than normal is anticipated in the Tennessee Valley, northern Rockies, Pacific Northwest and Hawaii. “Other regions have equal chances of drier, wetter or near-normal precipitation,” the agency said.