Washington, D.C. Oct 22, 2001 (AP by Randolph E. Schmid)--Sharp swings in temperature and rain or snowfall are likely this coming winter, with a threat of heavy lake-effect snows and Nor'easters.
The National Weather Service said Thursday that in many parts of the country the weather will be similar to last winter.
``Citizens should prepare for the full range of winter weather,'' said Scott Gudes, head of the National Oceanic and Atmospheric Administration.
``We don't expect a repeat of the record-breaking cold temperatures of November-December of last year, but this winter should be cooler than the warm winters of the late 1990s,'' Gudes said.
This winter, better technologies will help National Weather Service forecasters pinpoint extreme weather, said National Weather Service director Jack Kelly.
He said the nation is likely to experience large temperature and precipitation swings during the winter.
Among the reasons for the expected variability, forecasters said, is the absence of the El Nino and La Nina phenomena. El Nino and La Nina involve either unusual warming or cooling of the water of the central Pacific Ocean. When they occur, it has a strong effect on climate in the United States and elsewhere. With neither of those acting strongly, winter weather becomes more variable.
In addition, the Arctic Oscillation is expected to influence the number of cold-air spurts in the South and Nor'easters on the East Coast.
The Arctic Oscillation varies during the season, affecting the circulation of air.
When it is in a positive phase, the mid-latitude jet stream shifts to the north and there is an increase in the number of warm days over much of the contiguous United States. In the negative phase, the high-latitude air flow is blocked near Greenland, resulting in an increase in the extreme cold days, especially from the Great Plains to the Southeast.
The regional outlook for this winter includes:
--Northeast: Colder-than-normal temperatures are expected. Snowfall for the entire region will depend on the fluctuations of the Arctic Oscillation.
--Mid-Atlantic States: Equal chances of above normal, normal or below-normal temperatures and rain or snow. Storm tracks could bring more snow than the winters of the late 1990s, but this largely depends on the Arctic Oscillation.
--Southeast: Should be drier than normal. Temperatures have an equal chance of averaging above normal, normal or below normal.
--Upper Midwest and Great Lakes: Temperatures should be lower than normal, with more subzero days than in recent winters. There are equal chances for cumulative precipitation to be above normal, normal or below normal.
--Northern Great Plains and Rockies: Below-normal temperatures with more subzero days than experienced on average during the winters of the late 1990s.
--Southern Plains: Wet and mild weather is more likely than in recent winters.
--Central Rockies: Expect equal chances of above normal, normal or below-normal precipitation and temperatures.
--Northwest: Equal chances for above normal, normal or below-normal rain and snow. Heavy coastal rains are more likely compared to the previous three winters. A repeat of the near-record dryness seen last winter is unlikely.
--Southwest: Warmer-than-normal temperatures in most of the region, except western California, and equal chances of above normal, normal or below-normal precipitation.
--Southwestern Alaska: Expect a wet winter.
--Hawaii and the rest of Alaska: Expect equal chance of above normal, normal or below normal temperatures and precipitation.
For more information log on to the National Oceanic and Atmospheric Administration website at: http://www.noaa.gov
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