In North America, September was the snowiest on record dating to the late 1960s. And in Siberia, the snow is going gangbusters so far this October. Some scientists suggest all of this snow so early in the year may be a harbinger of a rough winter for the U.S. and Europe.
Judah Cohen, director of seasonal forecasting at Atmospheric and Environmental Research (AER), a unit of Verisk Climate, believes the North American snow tilts the odds towards a cold winter. “I would consider it at least a cold bias for this upcoming winter,” he said. “I remember that North American snow cover extent got off to a fast start in 2000 and that did portend a cold winter.”
Snow fell early in North America, including in places that rarely see it in September.
“[C]learly the [Canadian Arctic] Archipelago caught snow earlier than usual,” said David Robinson, New Jersey state climatologist who maintains a dataset for snow cover in the Northern Hemisphere. “Some snow on the mainland tundra of Canada and Alaska too, up into the Brooks Range and northern Rockies. That amazing Calgary snow event shows up.”
Links: Heavy, early-season snow in Calgary causes power outages, dangerous roads | Rapid City sees earliest snowfall on record as winter weather plunges into U.S. | Record cold and snow blast Rockies, with over a week left in summer
But research linking North America fall snow and winter weather is thin. “I’ve not come across something related to September North American extent and any subsequent connections over North America or elsewhere,” Rutgers’ Robinson said.
Siberia snow “off to the races”
While the link between North America snow cover early in the fall and conditions in the forthcoming winter may be considered speculative, studies have documented a more solid connection between October Siberian snow cover and the coming cold season.
The studies show that when Siberian snow cover extent is prosperous and increases rapidly in October, it provides a strong signal that a weather pattern known as the Arctic Oscillation (AO) will tend towards its negative phase during the winter months (December through March).
When the AO is negative, frigid air spills south from the Arctic and temperatures are usually colder than average over eastern North America and western Europe.
“[Siberian] snow cover has really picked up, it has rapidly advanced over the last week,” Cohen said. “It’s ahead of anything since at least [the year] 2000.”
He added: “Normally on this date there is about 1 million squared kilometers of snow cover south of 60°N across Eurasia and instead this year there is 5 million.”
Siberia already buried in snow. pic.twitter.com/ZOKIpeqw1Z— Ryan Maue (@RyanMaue) October 13, 2014
Cohen says this snow cover is a “robust, strong signal” for a negative AO this winter. He offered a sneak preview of his winter outlook, which he issues in November. “A negative AO favors a cold U.S., but I won’t say more than that,” he said.
While this forecast may have you stocking up on firewood, Cohen cautions this forecast could bust. “AO is a definitely better predictor for Eurasia than for the U.S.,” he said.
The “snow coverage punch bowl” over Siberia has not only caught the attention of Cohen, but also the National Weather Service forecast office in Philadelphia. On Sunday, it posted statistics connecting October Siberia snow and Philadelphia winter snow that surely has snow lovers drooling. From its Facebook page:
The snow coverage in Eurasia (Asia in particular) this month is off to the races. Since snow coverage has been mapped in the satellite era, Octobers with above average snow coverage in Eurasia have increased the chances of a snowy than normal winter in Philadelphia to about 50%. Take away the above average snow coverage punch bowl and past winters have been snowier than average only 22% of the time. Not only has it been snowier, but 6 of the 7 blockbuster winters (40″ or more) in Philadelphia have occurred after above average Eurasian snow coverage Octobers.
Of course, the AO is one of just many factors that influences winter weather in the U.S. Another key factor is El Nino.
If El Nino forms, it generally favors cool and damp conditions in the southern U.S., and warm and dry conditions in the north, relative to normal. The National Weather Service Climate Prediction Center currently forecasts a 60-65 percent chance El Nino will develop by the winter.
The Climate Prediction Center preliminary winter outlook reflects a weak El Nino pattern but does not appear to take into account the pre-season signal for a negative AO. Its official winter outlook will be released this Thursday, October 16.