Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 2:06 PM GMT on January 21, 2014
It's "The Return of the Polar Vortex" over the much of the eastern half of the U.S. this week, as another round of bitterly cold Arctic air plunges southwards out of Canada. Like many sequels, "The Return of the Polar Vortex" will not be as impressive as the original, with temperatures averaging about ten degrees warmer than during the original Polar Vortex episode earlier this January. Still, with temperatures 15 - 25° colder than average expected over much of the eastern half of the U.S. Tuesday through Thursday, this week's sequel is a respectable cold blast. The cold air is centered over the Upper Midwest, and low temperatures in portions of Minnesota, Wisconsin, and Michigan dropped below -20° early Tuesday morning. Crane Lake, Minnesota bottomed out at a bone-chilling -32°F this morning, and Pellston, Michigan hit -25°.
On Wednesday, the cold air spills southeastwards over much of the Ohio Valley, Mid-Atlantic, and New England, in the wake of Winter Storm Janus. The powerful storm is expected to bring 4 - 8" of snow to Washington D.C. on Tuesday, and 6 - 12" to Philadelphia, New York City, Providence, and Boston, Tuesday night through Wednesday. The most dangerous conditions are expected on Cape Cod, Massachusetts, where 8 - 12" of snow with sustained winds of 20 - 30 mph, gusting to 50 mph are expected. A blizzard warning is posted there.
Figure 1. Lake Erie lies 90% covered in ice on January 9, 2014, after the intense "Polar Vortex" cold air outbreak over eastern North America that week. The cold air brought the Great Lakes their highest ice coverage in 20 years for that time of year. Image credit: NASA Earth Observatory.
What is the Polar Vortex?
It's curious that the media latched on to the term "Polar Vortex" earlier this month. It's a term that has been around for a long time, but is generally not used by meteorologists in their public discussions of weather, since it is a rather technical term. NOAA has this explainer of the Polar Vortex, and TWC meteorologist Stu Ostro also has a nice description in his latest blog post, Polar Vortex, Global Warming, and Cold Weather. A short excerpt here:
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