Saturday, November 19, 2011

GFS Shows Arctic Oscillation Nosediving; Matches Up with ECMWF Theory of Strong Trough in Upper Midwest

Last 4 GFS Mode Arctic Oscillation Runs with Past Values and Ensemble Predictions

Today's 12z ECMWF Forecast on November 29. Shown in 500 mb heights.
The past couple GFS model runs have shown a true nosedive in the Arctic Oscillation forecast going into the late November period. The thing about it is, since the GFS has been indicating a nosedive for more than 3 runs, we like to call that a 'trend'. More interesting is how this Arctic Oscillation nosedive occurs as today's 12z ECMWF predicts a massive trough to cross the Upper Midwest as indicated by the 500mb chart just above. This ECMWF model, should it verify, would likely give the Upper Midwest snow and possibly some intense thunderstorms in the south. It's hard to tell since this system is projected to be very strong. The strength of the storm only makes it more volatile.
Since the Arctic Oscillation is very closely related to the North Atlantic Oscillation, it is possible that the NAO may go negative if the AO does as well. 

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