Remember how evidence was mounting last month that early snowfall was accumulating across Siberia? And remember how there’s a theory that says this snowfall signals a cold winter?
So in the two and a half weeks since, the news for the winter-haters has, unfortunately, only gotten worse.
About 14.1 million square kilometers of snow blanketed Siberia at the end of October, the second most in records going back to 1967, according to Rutgers University’s Global Snow Lab. The record was in 1976, which broke a streak of mild winters in the eastern U.S. In addition, the speed at which snow has covered the region is the fastest since at least 1998.
Taken together they signal greater chances for frigid air to spill out of the Arctic into more temperate regions of North America, Europe and Asia, said Judah Cohen, director of seasonal forecasting at Atmospheric and Environmental Research in Lexington, Massachusetts, who developed the theory linking Siberian snow with winter weather.
“A rapid advance of Eurasian snow cover during the month of October favors that the upcoming winter will be cold across the Northern Hemisphere,” Cohen said in an interview yesterday. “This past October the signal was quite robust.”
There are a few steps to get from the snows of Siberia to the chills in New York City.
Cold air builds over the expanse of snow, strengthening the pressure system known as a Siberian high. The high weakens the winds that circle the North Pole, allowing the cold air to leak into the lower latitudes. The term Polar Vortex actually refers to those winds, not the frigid weather.
Cohen said he first noticed the relationship between the Eurasian snow cover and larger weather patterns while doing post-doctoral work at the Massachusetts Institute of Technology in the 1990s.
It came about by chance because the original assignment was to look at the North American snow cover, Cohen said. He changed it to Eurasian and “when we investigated further it turned out it was Eurasian snow cover that was the dominant influence.”
Last year, 12.85 million square kilometers covered Eurasia at the end of October. By January, waves of frigid air were pummeling the U.S. Prices for natural gas, a heating fuel used by half of American households, rose to a five-year high in February.
“The big early snowbuild will definitely set things up for a cold back half of the winter,” said Todd Crawford, a meteorologist at commercial forecaster WSI in Andover, Massachusetts.
When the snow across Eurasia began piling up again this October, many forecasters and energy traders began to take note.
By Oct. 13, Cohen had calculated, 12.2 million square kilometers of Eurasia were covered by snow, compared with 10.8 million the same day last year.
Not everyone is convinced.
Mike Halpert, acting director of the U.S. Climate Prediction Center in College Park, Maryland, told reporters last month that there wasn’t enough historical information to make the Siberian snow rule a useful tool.
The climate center’s forecast calls for a greater chance for a mild winter along the West Coast and then across the northern U.S. states into New England.
Matt Rogers, a commercial forecaster in Bethesda, Maryland, said that while the snow accumulation isn’t a perfect predictor, he does keep an eye on it to help make seasonal calls for energy clients.
“I believe it increases the chances of a cold winter, but it does not guarantee it,” said Rogers, president of Commodity Weather Group LLC in Bethesda, Maryland. “I’ve seen some failures of it before.”
Rogers said for the U.S. East Coast, it’s important to watch the North Atlantic Oscillation, which often acts in tandem the Arctic one.
The oscillation is a shift of high and low pressure systems over the ocean that can influence storm tracks and the location of the jet stream, and affect the weather over the eastern U.S. and western Europe.
For Cohen, this year presents a good opportunity to test the theory. After seeing this much snow pile up, a balmy January and February in the eastern U.S. would undercut the thesis.
Cohen said he has started a blog to track the changes in the Arctic oscillation and what happens with temperatures this season.
“It is an important year,” Cohen said, “because it is a big number for the snow.”