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Forecasters Predict a Normal Winter Season
By Amanda Onion
Oct. 13 Brace yourself for a real winter.
The nations top climate and weather experts are predicting that the string of relatively mild winters in recent years may be coming to an end now that the quirky weather influences of La Nina and El Nino have faded.
Weve probably forgotten over the last three years what a normal winter is like, says D. James Baker, administrator for the National Oceanic and Atmospheric Administration. With La Nina and El Nino out of the way, normal winter weather has a chance to return to the United States this year.
What qualifies as normal winter weather?
Snow, Rain and Cold
In the Northeast, skiers have reason to be happy since it could mean a greater chance of snow and cooler temperatures that dip an average of 4 degrees below the averages of the previous three winters. In the Plains states and the Midwest, cold air outbreaks could lead to more bone-chilling days below zero.
Famously cold cities could feel even colder. The forecasters predict people in Chicago will experience average temperatures 6 degrees colder than the past few winters, and those in Minneapolis will need to bundle up against temperatures 7 degrees below the previous three years averages.
Florida is expected to be slightly warmer than recent winters, but it might also be punctuated by cold air outbreaks, known as Florida Freezes. Other states in the southeast are predicted to be soggier than in previous winters, as is California, thanks to a tropical jet stream. Finally, areas in the West and Southwest, except California and Nevada, are likely to be warmer than usual while the Northwest is likely to experience heavy rain as usual.
If that forecast sounds like a mixed bag, thats just the point, says Baker.
Weve had a lot of experience with neutral winters and we know you get close to average temperatures, but you also get a lot of swings from the polar jet stream dipping down over the United States, he says. So we expect extremes.
Normal Equals Erratic
A neutral winter is one where neither an El Nino nor a La Nina are at play. An El Nino, such as the one that wrought floods, hurricanes and tornadoes around the world between 1997-1998, is a warming of tropical waters in the Pacific. And a La Nina, like the one which just faded this summer, is the opposite a cooling of waters in the Pacific.
Baker explains the past three winters have been unusually warm since El Nino leads to warmer temperatures in the south, while La Nina generates warmer temperatures in the north.
But for the first time in three years, waters in the Tropical Pacific arent running unusually cold or warm this year. As Nicholas Graham, a meteorologist at the University of California in San Diego, explains, Right now were between the two, the climate system isnt being forced in any particular direction. So were back to normal.
Back to normal means back to slightly colder temperature averages and erratic storms. But of course, thats only a prediction. And in a season like this, predictions are even less certain.
With a big El Nino going on, its pretty easy to gage the forecast. But now there are so many other, smaller variables, says Graham. The climate system is chaotic and all you can do is predict probability.
A Telling Season
Another factor that the national forecasters fed into their computer-generated prediction models, is a slight warming trend. A recent federal assessment showed that overall global temperatures have risen by about one degree in the 20th century. And recent data suggest that increase has accelerated in recent years. Some scientists attribute that warming to the so-called Greenhouse effect, which is caused when gases from cars, factories and other sources, trap solar heat inside the Earths atmosphere.
Recently winters havent been very normal, says Graham. So it will be a good test to see if the climate has changed and whether we can still experience an old fashioned kind of winter.
-- (firstname.lastname@example.org), October 15, 2000