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Winter storm raises the question: What's going on with the weather?

This week's winter storm – and others before it – are being influenced by climate patterns in the Arctic and North Atlantic. Scientists are working to understand how these patterns work.

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A pedestrian walks through Chicago Wednesday after a winter storm dumped nearly 20 inches of snow on the area overnight.

M. Spencer Green/AP

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In Chicago, they called it the Blizzard of 2011. At Accuweather, a forecasting service, it was known as the Groundhog Storm.

By whatever name, the vast winter storm that spun its way across the US in the opening days of February is but one sign that this winter will be memorable.

Indeed, this winter marks the second in a row during which closely related, large-scale climate patterns over the Arctic and North Atlantic have combined to deliver biting temperatures and heavy snowfall to the eastern half of the country – including spots where snowfall is rare.

In particular, the weakening of a high-altitude polar wind has allowed cold air to dip southward more often than usual, and pressures over the North Atlantic have aided in slotting storm after storm into similar tracks across the US.

Scientists caution that it is far too early to speculate on whether these climate patterns are part of a new normal for North American winters. Over the long term, none of the storms this winter or last are unprecedented, notes Deke Arndt, who heads the climate monitoring branch at the federal government’s National Climatic Data Center (NCDC) in Asheville, N.C.

But they raise questions, and scientists are looking a wide range of data – from summer sea-ice levels in the Arctic to rainfall over the Indian Ocean – to better understand the global mechanics behind when and how these climate patterns shift.

To be sure, the past two winters “have not been like the slew of winters we’ve seen over the past couple of decades,” says Mr. Arndt.

The Deep South and Southeast have experienced bouts of deep freeze and snowfall they typically don’t experience. Meanwhile, the West has experienced warmer-than-usual winter temperatures – a trend that was perhaps most obvious last winter when the Vancouver Winter Olympics were deluged by rain.

A heavy-hitting lineup

This January’s lineup of storms highlights the point.

Between Jan. 9 and Jan. 13, for instance, a storm system brought heavy snow and freezing rain to a broad swath of the South and East. In the Southeast, Bakersville, N.C., recorded 20 inches of snow, while the storm brought 24 inches to Windsor Lock, Conn. Once the storm passed, 49 of the 50 states had some level of snow cover.

Between Jan. 25 and 27 another storm system blanketed large portions of the eastern US in snow. The heaviest snows fell on the Northeast, with New York reporting thundersnow and 19 inches of new snow in Central Park. According to NCDC records, the storm was among the Top 10 for snowfall in New York and Philadelphia.

Likewise, more snowfall records have been set around the country than record-low temperatures this winter. In December and January, only 12 communities broke or tied previous low-temperature records. But 202 communities broke single-storm snowfall records, while 54 more tied a previous record.

Most of the snowfall records are topped by an additional inch or two of snow. Not so in Siloam, Ga., 76 miles east of Atlanta. Siloam’s previous record boasted a “trace” of snow on Dec. 3, 1971. A storm that hit the area on Dec. 26 dumped 10 inches of white stuff on the community, according to NCDC data.

Meanwhile, total snowfall in December and January for major eastern cities is running well ahead of last year, according to data gathered by Accuweather. New York tops the list. By Jan. 31, 2010, the city had seen 14.5 inches of snow. As of Jan. 31, 2011, slightly more than 56 inches had fallen on the Big Apple.

On the other hand, Washington, D.C., has been catching a break. Last year, the nation’s capital had received 24 inches of snow between December 2009 and January 2010; for the same period this winter, storms have brought nine inches of snow.

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