Andy Revkin of the New York Times posted a fascinating story on his Dot Earth blog today summarizing new research linking fall snow cover in Siberia to winter weather patterns and temperatures over North America and Europe. The research, performed by climate analyst Judah Cohen of Atmospheric and Environmental Research and colleagues at MIT, is funded by the National Science Foundation (NSF). NSF describes the linkage (see this figure for an illustration) accordingly:
When [autumn] snowfall is high in Siberia, the resultant cold air enhances atmospheric disturbances, which propagate into the upper level of the atmosphere, or stratosphere, warming the polar vortex. When the polar vortex warms, the jet stream is pushed south leading to colder winters across the eastern United states and Europe. Conversely, under these conditions the Arctic will have a warmer than average winter.
Based on these relationships, Cohen has developed a seasonal forecast model. In a special report on this work, NSF states that Cohen's model predicts "below normal temperatures for the Eastern U.S." this coming January through March (as shown in the figure above) due to above normal snow cover observed in Siberia during October.
Cohen's model correctly predicted last winter's cold in the Eastern U.S. as well as the cold observed during the winter of 2002-2003 according to NSF. The model has also demonstrated skill in Europe and was "significantly more accurate than [forecasts] issued by the European forecast centers" last winter according to NSF.
The prediction of a cold January through March in the East is at odds with Capital Weather Gang's winter outlook for warmer than average temperatures in January and February in the D.C. metro region. We'll take a closer look Cohen et al.'s research in relation to other seasonal forecasting methodologies in a future post.