Upper Air Analysis of a Storm

Date : 23 February 1999

Let's consider how upper air flow affects development of weather systems. My article illustrating a detailed surface analysis (not here yet) concerned a small storm system most typical of those in North America. This one features the more unusual (and probably interesting) case of a large snowstorm, which dropped 2 feet at most favorable locations near the southern west shore of Lake Michigan and more than a foot over much of the Great Lakes region. This article involves detailed analyses of 500 mb and 850 mb charts, precipitation type and its relation with predictive weather parameters, and snowfall maps.

Large Scale Features

The storm occurred 2-3 January 1999, as a strong cyclone developed over the southern Plains states and strengthened while moving over the Great Lakes. A peek at the associated large scale weather patterns as depicted on Unysis' WXP weather chart archive is helpful. The primary features you should notice are development and movement of the surface cyclone between 1 & 4 January,

Surface chart : 1 January 1999, 00 UTC
Surface chart : 1 January 1999, 12 UTC
Surface chart : 2 January 1999, 00 UTC
Surface chart : 2 January 1999, 12 UTC
Surface chart : 3 January 1999, 00 UTC
Surface chart : 3 January 1999, 12 UTC
Surface chart : 4 January 1999, 00 UTC

that such development occurred in a region of large temperature gradient (temperature shown at upper left of each station plot), and the associated upper air situation - particularly at 500 mb (middle atmosphere) the trof aloft which develops in the flow over the NW U.S. and strengthens while moving southeastward, and the cold closed Low which subsequently formed over the middle U.S.

Detailed Analysis

Many upper air charts are presented, showing the storm's evolution and relevant features. 1.86 MB of 17 charts must load, so please be patient. Make sure your Disk Cache is @ least 2048 kB (using Netscape, click Edit, Preferences, Advanced, then Cache - probably something similar for other browsers) and grab a snack or something You can e-mail me for suggestions if you have trouble downloading everything. I think showing these is quite useful, so I place them and the related discussion on a separate page (same link as above).

Next

Hopefully this retrospective analysis of a major snowstorm was an instructive example. Many more aspects can be discussed, but the above is most helpful for achieving our goal of forecasting such events, which we'll soon be doing here.


Text is copyright of Joseph Bartlo, though may be used with proper crediting.

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