Some Signs of Winter on Horizon

Another major weather pattern change will take place next week across the Northern Hemisphere. November, so far, has been 3 degrees below normal but the past 2 days have average above normal.

The reason for the early November chill has been a negative NAO and a deep and persistent trough and closed low across the east coast which has brought in a chilly, cloudy northeast flow along with unseasonably cool low level temperatures from the north. Remember Monday’s snow?

That has all come to an end, for now, with a gorgeous stretch of sunshine and above normal temperatures.
The above image is a great description of the current pattern. The colors are height anomalies (departure from average) while the lines are 500mb heights (higher heights, in general, indicate a ridge of high pressure and warmer weather). For the next couple days a large omega block will be in place. An omega block gets its name from the greek letter Omega (they look alike) and features 2 closed low on either side (the easternmost low is the one that stalled out and gave us snow on Monday). Underneath the ridge we can expect fair and unseasonably warm weather with temperatures coming close to 60 on Saturday!

At the same time across the Pacific a +EPO pattern is in place which corresponds to a closed low over the Gulf of Alaska and ridging over southeast Canada. Pretty much exactly what we have now.

Fast forward 180 hours and this is what the GFS ensemble mean shows.

A completely opposite pattern develops. A ridge develops over the Gulf of Alaska (-EPO) and a Rex Block develops over eastern Russia with a huge ridge over the Bering Strait and Kamchatka. This effectively dislodges any cold over the North Pole and sends it south into the Northern Plains. Some of this cold will spill east but the extent of that cold is up in the air. It seems likely, however, that by the end of next week and Thanksgiving week a below normal and potential wintry weather pattern will take shape across most of the northeastern and north central United States. I don’t expect bitter cold but I wouldn’t be shocked to see a snow or ice threat out of this.


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