Last year, the snow level across Eurasia was the fourth highest for the month in records going back to 1967. In January, frigid temperatures dubbed “the polar vortex” slid out of the Arctic to freeze large portions of the U.S.
It was a pattern that repeated itself during the Northern Hemisphere winter and helped make the first three months of this year the coldest in the 48 contiguous states since 1985, according to the National Climatic Data Center in Asheville, North Carolina. With the snow now piling up across Eurasia, will this winter be a grim reminder of last year’s?
“It’s still early in the game,” said Judah Cohen, director of seasonal forecasting at Atmospheric and Environmental Research in Lexington, Massachusetts, a division of Verisk Climate.
While “the snow has gotten off to an incredible start,” Cohen said he needs to see how much covers the area through the entire month before he can make an accurate forecast. The National Science Foundation has sponsored his research into the link between Eurasian snowcover and the severity of the Northern Hemisphere’s winter.
As of Oct. 13, Cohen calculated, 12.2 million square kilometers of Eurasia were covered by snow, compared with 10.8 million square kilometers on the same day last year.
About 12.9 million square kilometers covered Eurasia in October 2013, according to the Rutgers University Global Snow Lab. The record was 17.2 million in 1976. It’s important to note that snowcover ebbs and flows and isn’t a constant all the way through the month. Last year, some of it melted away before Oct. 31 arrived. Cohen said the same may happen this year.
Cohen is trying to understand what makes snow pile up in Eurasia. His hypothesis is that the melting of the Arctic ice cap has put more moisture into the atmosphere, which provides fuel for the higher snowfall. He said he hasn’t been able to discover a solid link between the two.
According to Cohen’s research, there is a link between the snowcover and how much cold spills out of the Arctic and where it ends up once it escapes.
A big piece of this depends on the North Atlantic Oscillation, or NAO, which is a pressure differential across the basin. When it’s in its negative phase, cold air can be bottled up across the eastern U.S., and that can also mean more snow both there and in Western Europe.
A good indication of what the negative phase of the NAO can do was the winter of 2009-2010, when 56.1 inches (142.5 centimeters) of snow fell in Washington and the “Snowmageddon” storm halted travel in the U.S. Northeast.
That was also the year when a satellite photo showed the U.K. covered with snow, Cohen said.
Cohen said we need to wait a few weeks before he’ll predict what the NAO will do.
“Our research has shown that you need all 31 days” of October, Cohen said. “A lot can go wrong.”