While forecasts more than two weeks ahead are not always accurate, there are growing signs of a shift in the global climate pattern that could bring much cooler air to the Eastern US in January.  The shift is related to projected changes in the strength and orientation of a band of high-altitude winds that make up what is commonly called the “polar vortex”. The computer models that look farthest ahead in time are showing that that vortex is showing signs of weakening and even the p.ossibility that it could temporarily split into two circulations, which would divert the flow of the coldest air down into our region. We’ll be watching the updated forecasts carefully to see if this colder pattern becomes more likely. You can get more information from the Capital Weather Gang here.

Visualization of stratospheric polar vortex on Dec. 18. (earth.nullschool.net)