From Russia, with snow: How Siberian weather predicts U.S. winter

If you want to know just how cold and snowy our winter will be, look no further than far away Siberia, the "refrigerator for the Northern Hemisphere," meteorologist Judah Cohen says. 

The amount of October snow cover across that vast Russia province thousands of miles away is the key to the winter forecasts Cohen puts out for the U.S. each year through Atmospheric and Environmental Research, a Verisk Analytics company.

An unusually snowy fall this year in the already perpetually frosty region means those in the central and eastern U.S. can expect a cold, snowy winter, Cohen says. 

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Here's how: Snow reflects about 70% to 80% of the sun's warmth back into space, while a bare ground reflects only 20%. October is when Siberia and the entire Eurasian region sees its greatest expansion of snow cover, sometimes increasing as much as six million square miles, larger than the total land area of the U.S., including Alaska.

Just how snow-covered Siberia gets in fall helps Cohen formulate his forecast because that icy cold air over the region will slowly slosh into Europe and eventually into North America by mid-winter. Essentially, more snow in Siberia equates to colder air and the potential for more snow than normal in the U.S.

The cycle also affects climate patterns, with more snow cover often resulting in the infamous polar vortex more frequently spilling frigid air down into the eastern U.S., or dipping temperatures even lower in a single cold spell. It also tends to turn the Arctic Oscillation climate pattern negative, another sign of a colder winter in the East.

While the central and eastern U.S. may shiver this winter as a result of the Siberian snow cover, the western U.S. should see a warmer-than-average winter partly because of the La Niña climate pattern, Cohen said. 

Siberia's snow doesn't typically affect the West's winter forecast because the cold air it helps funnel down from the Arctic tends to get blocked by the region's mountains, and it doesn't play a role in precipitation there either.

Cohen, whose research is funded by the National Science Foundation, said he found the link between Siberia's snow cover and U.S. weather by accident. As a postdoctoral fellow, he ran global climate modeling experiments to determine the influence of unusual North American snow cover over other large-scale climate patterns.

Instead, he found the strong relationship that now forms the basis of his predictions, which he says have been 75% accurate since he began including Siberian snow cover as a factor in winter forecasts in 1999. 

Government scientists have yet to use the technique in the official federal forecast issued each year, instead relying primarily on the climate patterns of El Niño and La Niña. Mike Halpert, director of the Climate Prediction Center, said the agency is aware of the research on the connection between Siberian and U.S. weather, but "these relationships are still being tested."

"It is not yet clear how they might improve predictions beyond the current set of tools that we already consider," he said.

Last winter, Cohen wasn't spot on in his forecast. His prediction that much of the country would experience warmer weather than usual panned out, but his forecast of cooler weather in the Southeast and mid-Atlantic states didn't quite hit the mark. The season ended up freakishly warm coast-to-coast and was the warmest on record, NOAA reported.

Cohen's predictions are once again at odds this year with the prediction center's forecast released last week that calls for a mild, dry winter for the southern U.S., and gives the East equal chances of a colder, snowier winter or a warmer, drier one.