Thursday, November 22, 2012

November 27-29 Potential Winter Storm Discussion (11/22)

Please note that yesterday's first call is now void, as I realized the data I was watching is incorrect. This post now includes my best thoughts on the situation.

Rather than clog up this post with a ton of images, here's my own manual analysis of the models as of the most recent 0z run. As you can see, the GFS, ECMWF ENS, GGEM, GGEM ENS, NOGAPS, NOGAPS ENS, ESRL ENS, NAEFS ENS, UKMET models and ensembles are all in agreement of a North Camp solution, where the storm system goes north and impacts the Midwest, Ohio Valley and eventually New England. The GFS ENS appear to be in the 'Middle Ground' in between the North Camp and South Camp (The South Camp goes through the South and goes up the East Coast), while the JMA, FIM and FIMZ models are unavailable for the time of analysis.

Curiously, the ECMWF is the only one going for the South Camp. I can't say I disagree entirely, as there will be a negative NAO in place. However, this negative NAO will be east-based, which, as the image above details, brings a stormy and cold pattern to the Midwest, Plains and Great Lakes, whereas a west-based negative NAO supports the cold and snow for the East Coast. For those of you wondering, an East-Based negative NAO literally means that the ridge of high pressure that causes the negative NAO is east of Greenland. In the west-based negative NAO, the ridge is west of Greenland.

Models are supporting the idea of an east-based negative NAO, which is why the heavy majority of models and ensembles are in favor of this North Track.

What the models are really having trouble diagnosing is the strength of this storm system against a ridge of high pressure which will be in place over the Southeast. If the low pressure system is weaker, the ridge will deflect it north. However, the ECMWF believes that the system itself is stronger, and that the Northeast is destined for this storm. While it has happened before where the ECMWF has been the only one to correctly predict such a scenario, nearly all of the ensembles (including the NAEFS and ESRL PSD) are going for the North track.

At the moment, I now favor the North Camp, not only thanks to the models, but as I described with the east-based negative NAO and ridge in the Southeast.

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