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Wetter-than-normal weather ahead; What the forecasters see for winter

Warm in the East, cold in the West, and wetter than normal over many parts of the United States. That's what some of the long-range weather forecasters expect this winter.

Recent near-record warmth along the US East Coast and floods, tornadoes, and other highly unsettled weather in the middle of the country appear to fit this pattern reasonably well.

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The winter forecast (December, January, February) of the National Weather Service (NWS) is expressed in terms of probabilities. It projects at least a 60 percent chance of above-normal temperatures from Florida to Connecticut. ''Normal,'' in this context, means the three-decade average for 1941-70. Most of New York and New England are given a 55 percent chance of above-normal temperatures. But for Maine the outlook is judged too close to call.

The temperature prospect for the middle of the country also is too uncertain to be assigned a probability. But the NWS projects at least a 55 percent probability of a colder-than-normal outlook from the Great Plains to the Pacific coast except along the southern US border and in the far Pacific Northwest. In the Great Salt Lake Region, the probability for a cold winter is 70 percent.

As for precipitation, the NWS expects, with at least a 55 percent probability , that much of the contiguous US will be wetter than normal. That includes the East Coast from Florida to New York and Connecticut, most of the South and lower Midwest, the Southwest between New Mexico and California, and Colorado and Wyoming. The Rocky Mountain region is expected to get a great deal of snow.

Donald L. Gilman, who heads the NWS predictions branch, sums up the forecast's ''main message'' as ''cold weather . . . in the West'' plus ''a lot of precipitation across the country.''

Jerome Namias of the Scripps Institution of Oceanography, a pioneer in long-range forecasting, agrees. He has issued a winter forecast calling for mild winter weather in the eastern third of the US with cold, wet weather over much of the western half of the country.

In more specific terms, the Namias forecast expects winter temperatures to be warmer than normal over most of the East and Gulf Coast states with above-normal precipitation over most of this region. Much of the precipitation would fall as rain or sleet. For much of the West - the Great Plains, northern Texas, the Northwest, and coastal California - he expects colder-than-normal temperatures. However, near-normal temperatures with large week-to-week fluctuations are expected for the remaining central area and far Southwest.

The forecast expects precipitation to be well above normal, except for near-normal amounts over the Pacific Northwest, the North Atlantic states, and the extreme Southwest. Over the Plains, the northern tier of states, and high elevations in the West, much of this will be snow.

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Hurd C. Willett of the Massachusetts Institute of Technology, the third meteorologist who regularly ''goes public'' with a winter forecast, seems to be the odd man out. He has said he expects unusual cold, perhaps ''the coldest of the century.'' He anticipates that New England, in particular, could be five to six degrees below normal with lows of 10 to 12 degrees below normal for some areas in January. Dr. Willett bases his forecast on a theory of how fluctuations in the sun's energy outflow, as evidenced by sunspots, affects weather. This theory, which is controversial among meteorologists, correlates cold weather with low sun-spot activity - a situation Willett now anticipates.

All three forecasts raise the question of how seriously one should take them. None of the meteorologists involved - Gilman, Namias, or Willett - claim any exceptional skill. But they do think they do better than flipping a coin.

Reflecting an assessment widely held among meteorologists, Namias has summed up the situation by pointing out that ''the modest success currently achievable has a long way to go before accomplishment of really reliable long-range forecasts.'' However, he added, ''Taking 50 percent as chance (climatological probability), something on the order of 65 percent to 70 percent for monthly and seasonal forecasts is a reasonable figure (for forecasting skill), although temperature is easier to predict than precipitation. . . . This skill matches or exceeds that of other geophysical predictions or economic forecasts.''

Mr. Namias admits he ''failed miserably'' to anticipate the severe weather that gripped much of the US for six weeks last January and February. He bases his forecast on sea surface temperatures, especially in the northern Pacific.

Ocean areas act as energy reservoirs that help drive large-scale weather patterns. Last year, Namias says, the relevant sea temperature patterns let him down. They were weak and disorganized. This year, however, they are well developed.

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