This winter an extreme one, but still within range of what can be expected

North America's cold snap is a strong contender to set a new weather record. But it is too soon to say whether or not we are having another severe winter as a whole.

This is the most a climatologist can say at present about the ''very exceptional'' weather much of the United States is experiencing, says Robert Quayle of the US National Climatic Center (NCC). Not only is much of the winter yet to come, but it will be several months before NCC will have assembled the data needed to determine what actually has happened across the nation.

The weather has been wreaking havoc across much of the nation, and may have been a contributory factor in the recent crash of an airliner in Washington.

But Mr. Quayle urges people to keep the present extreme weather in perspective. ''When something like this happens, people wonder if the glaciers are heading for Miami,'' he says. But, he adds, ''we are not looking at a change of climate, only at one of the meanders around a normal average. It is extremely unusual, but the science of statistics teaches us we should expect the extremely unusual.''

Indeed, the cold snap is only one of a number of extreme weather situations that have hit the continental United States over the past half decade or so. A study by Douglas Hoyt of the National Center for Atmospheric Research has shown that such extremes are within the range of what can be expected for the present climate. Nevertheless, when each of them occurred, it was cause for news media speculation about climatic change. The following are a few examples.

* Last winter (1980-81) nationwide had the driest January since 1895, while February was the second driest period on record. That was the 48-state average. Some individual states broke their drought records. For example, Idaho, Illinois , Indiana, Iowa, and Kentucky had their driest Januaries while Delaware and Louisiana experienced their driest winters ever.

* The previous summer (1980) brought a heat wave and drought to much of the nation. The National Oceanic and Atmospheric Administration estimates it cost the country nearly $20 billion in crop and livestock loses, excessive electricity use for air conditioning (5.5 percent above normal, a record), and other damages. In South Central and Midwestern states miles of highways buckled.

* Most remarkable of all the recent weather extremes was the run of three very cold winters in a row -- 1976-77, 1977-78, and 1978-79. Indeed, describing the last of these three winters, A. James Wagner of the National Weather Service's Long Range Prediction Group has emphasized its severity by noting: ''Although the entire country was not in the deep freeze for the whole winter, mild spells were so weak and transient relative to the intensity and duration of the cold periods that nearly every weather station in the 'Lower 48' recorded below-normal average temperatures for the winter as a whole.''

It is in the perspective of this recent history of weather extremes that Mr. Quayle says one should consider the present cold spell. ''It may not be the coldest cold wave of the century,'' he says, ''but it is a contender.'' But he emphasizes it is not unprecedented.

What may be unprecedented, he adds, is the run of extreme winters from 1976 to 1979. If 1981-82 turns out to be another such winter, then, he says, we will have a very unusual run of weather indeed.

At this writing, the National Weather Service's 30-day forecast suggests that such a cold winter may occur.

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