Meteorological winter is upon us, and if you’re wondering what the next few months have in store weather-wise, you have a few options. There’s always the Farmer’s Almanac which – by the way – is predicting a cold, snowy winter here in New England. If you want something more scientific, there’s the The National Weather Service's winter weather outlook, which is calling for warmer than average winter temperatures in the northeast.
But Lexington-based Atmospheric and Environmental Research (AER) has been producing their own winter weather forecasts for almost two decades, and they often look very different. This year, AER's Director of Seasonal Forecasting, Judah Cohen, is calling for colder than average temperatures along much of the east coast and into New England. He says there's also the possibility that Boston will see a snowy winter.
The difference is a reflection of the parts of the world the forecasters' computer models pay most attention. The National Weather Service outlooks, and most climate models, focus primarily on the connection between El Nino/La Nina (cycles of warmer and cooler water temperatures in the tropical Pacific Ocean) and weather in the continental U.S. But that connection is stronger in the south and west than it is in the northeast.
As a young researcher, Cohen stumbled on a totally different set of factors - in a totally different part of the world - that are strongly correlated with winter weather conditions in the northeast. He now bases his forecasts largely on three things: autumn snow cover in Siberia, the concentration of Arctic sea ice, and the extent of atmospheric "blocking" affecting the flow of the jet stream.
Ironically, when the Arctic is warmer, the northeast tends to see colder, snowier conditions (remember the polar vortex?). And since the Arctic is warming at least twice as fast as the rest of the globe, that could be the direction our winters are headed on a more regular basis.
Cohen's work remains controversial. He and other researchers haven't yet nailed down the mechanism that connects Arctic warming to cold, snowy winters in the northeast. And climate models don't represent that connection. Cohen says that, eventually, he hopes his work can help improve those models.
In the meantime, the snow lover is pulling out his snow shovels and skis, and hoping his forecast comes true.