The Past and Future ChillNovember 14th, 2013 at 10:36 pm by Bill Steffen under Bill's Blog, Weather
Click the image to enlarge. This map from the High Plains Regional Climate Center shows a large part of the country (in the color green) has seen below average temperatures over the past month. The areas in blue have been more than four degrees cooler than average. Now, check out the Arctic Oscillation (going down), the North Atlantic Oscillation (going down) and the Pacific North America Pattern (going up). When the Arctic Oscillation goes negative, the North Atlantic Oscillation goes negative and the Pacific North America Pattern goes positive, that usually means an upper level trough in the East and a ridge in the West. That would mean NW flow over the Great Lakes and the ability of cold air from Canada to push south into the U.S. Check out the North American snowcover (note the snow that was on the ground this (Thurs.) morning in Berrien Co. Michigan and La Porte Co. Indiana). Most of Canada has snow on the ground. Most of the lakes north of Lake Winnipeg are frozen now and ice is already starting to form on the west side of Hudson Bay. The GFS long-range models show a lot of cold air over Canada at the end of the month, and it looks like Old Man Winter is going to spending some time in Michigan and the Northern U.S. in the first half of December. Lake Michigan is 48 degrees and in December it’ll hang around 39 degrees as the lake overturns (kudos to the Dept. of Geology at Grand Valley for the explanation). There’s certainly the potential for a good lake-effect event.