Tuesday, September 9, 2014

September 10th Potentially Significant Severe Weather Event

A severe weather event looks to unfold on Wednesday, September 10th that may hold the potential for significant damaging winds, as well as tornadoes.

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The Storm Prediction Center's severe weather outlook for tomorrow shows a wide swath of the Midwest and Ohio Valley under the gun. States outlined include nearly all of Illinois, all of Indiana, eastern Missouri, much of Michigan, and a heavy majority of Ohio.

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A probabilistic approach to the outlook for tomorrow can better define who's in line for the worst weather. In the image above, we see the SPC has delineated the severe weather risk into four categories. The lowest category, the 5% chance of severe weather area, indicates thunderstorms can be expected, but shouldn't reach severe limits. The 15% delineation describes severe thunderstorms as being possible, but probably not widespread. The 30% outlook indicates severe thunderstorms may form en masse, with modes of significant severe weather possible. Those in the 45% outlook may want to prepare for widespread significant severe weather, which may threaten life and property. This 45% outlook zone is focused across eastern Illinois into Indiana, northwest Ohio, and southern Michigan.

High-resolution radar forecast from the 4km NAM model shows thunderstorm formation around 7:00 PM Central time / 8:00 PM Eastern time on Wednesday. This ragged squall line originally is composed of individual cells, which tells me tornadoes may be a threat. This potential tornado threat is highlighted by the incredibly dynamic wind fields aloft, owing to the very strong low pressure system passing to the northwest. These cells then congeal into a squall line, which could be capable of producing large areas of potentially damaging winds.

A good deal of uncertainty remains with this event, but the potential is there. Make sure you're prepared.


1 comment:

Christopher Ebie said...

Thanks Andrew, for your post. I am in that 45% probability in southern Michigan so I will keep on the alert.