Saturday, June 14, 2014

Potentially Significant Severe Weather Discussion for Thursday, June 19

(Click here for the discussion concerning Wednesday's severe weather threat)

Thursday's severe weather event is looking far more threatening than initially thought.

In the Weather Prediction Center's surface analysis forecast for Thursday, we see the storm system centered in southwestern Minnesota slowly shifting eastward. A warm front is draped across Wisconsin and Michigan, heralding the boundary between the seasonal air mass and the hot, humid and unstable air mass to the frontal boundary's south. A cold front is then projected to meander eastward, as it is attached to the low pressure system from Minnesota down to Texas. Based on the location of the frontal boundaries, and anticipated wind fields due to the upper level low, I'm watching Iowa, Illinois, Wisconsin, Missouri, Kansas and Indiana for severe weather threats on this particular day.

We can also use analog dates to predict the future. This method of forecasting takes decades of weather observations and matches a handful of select dates up that are closest to the forecasted conditions. This image shows compiled severe weather reports from the top 15 analog dates, basically the 15 days that were the closest to projected conditions on Thursday evening. If we take a glance at all of these severe weather reports, it is clear that environments similar to what we may see on Thursday tend to produce significant severe weather episodes. In this image, we see significant tornado, damaging wind, and hail reports from North Dakota to Oklahoma and Texas, and from Ohio to Michigan. The states of Illinois, Iowa, Minnesota, Wisconsin, Nebraska and Kansas look to be hit awfully hard in these types of set-ups. While these analog projections cannot exactly predict where severe weather may strike, and with what vigor, it's clear by the number and frequency of severe weather reports that residents in the aforementioned states should keep both eyes to the skies on Thursday, if current forecasts hold.

The folks at the institute that compiles all of these analog dates also makes an image that essentially takes the frequency and intensity of all of the above severe weather reports, and puts them into a probabilistic scale of receiving severe weather in the form of a tornado, hail, or damaging winds, based on the top eight analogs. According to this image, if current forecasts hold, residents of Illinois and Iowa could have over a 60% chance of seeing some type of severe weather. Needless to say, that is an awfully high risk, and one that must be paid close attention to. Residents of Wisconsin, Missouri, Kansas and Oklahoma would still have a very-respectable 45% to 59% chance of severe weather based on all of these analogs. This is all concerning to me, and warrants the issuance of a new severe weather discussion.


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