Thursday, March 1, 2012

3:30pm Weather Update

Wanted to add an additional thought concerning tomorrow's potential severe weather. I have to give credit to the National Weather Service forecast office in Paducah for bringing up this idea. The cap. Yeah, a cap like the ball cap you wear.

The cap is basically having warm air aloft that keeps parcels of air from rising above a certain level. The cap is often at play during the summer when it is warm through the air column. It is in place when you go outside and watch clouds build up. They keep going and going, but then all of a sudden they seem to just stop and they don't become much. BUT, there's that one cloud that has enough "oomph" to break through and explode upward eventually becoming a decent thunderstorm.

Both the NAM and GFS models are predicting that a cap will move in for southeast Missouri, southern Illinois, western Kentucky and central Indiana behind the warm front.

When looking at the below numbers, the lower the number, the stronger the cap. (Look carefully, the numbers go negative.)

Here is the NAM at 6am CT.


Here is the NAM at 12pm CT.


You can see that the NAM begins to erode the cap as we go through the day.

Here is the GFS at 6am CT.


The question becomes "Does the cap erode enough while the ingredients for thunderstorms are there?" If the answer is yes, we will see thunderstorms build up. If the answer is no, the thunderstorms may initialize further east.

Again, props to the forecasters at the Paducah NWS office for catching that. I hadn't looked that closely to all of the data to catch that detail.

I should also note that this afternoon's high resolution 4km and 12km computer models are backing off on the late morning/afternoon thunderstorm development for southeast Missouri, southern Illinois and extreme western Kentucky.

I think the brunt of the action will be over central Kentucky and central Tennessee. Places like Lexington, Bowling Green and Nashville.

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