Wednesday, April 21, 2010

Severe Storms appear likely Friday

As we move closer to the weekend it is appearing more likely that a severe weather event will occur across Parts of East Texas Friday afternoon and evening. The Storm Prediction Center currently has a large area of the Plains and Midwest under a slight risk of severe weather Friday, including all of East Texas. It looks as though parts of East Texas could be upgraded to at least a moderate risk of severe weather, mainly north of I-20.



Severe weather will begin to break out this afternoon across the Texas Panhandle as a strong storm system begins to take shape. This storm system will move to our north on Friday dragging a dryline and a cold front into East Texas. Right now the atmosphere is forecast to be conducive for very large hail, larger than golf balls, gusty winds, and isolated tornadoes. The forecast hodograph for Friday afternoon shows a tremendous turning of the wind with height. The large clockwise turning is favorable for tornadoes however, in the lowest 1km of the atmosphere; the turning of winds is not as great. So I do believe we will see an isolated tornado or two but right now it does not look as though we are looking at a major tornado outbreak. I will add many times with an atmospheric set up like we will have Friday, storms will move slightly faster and more to the right than forecast. This will greatly increase the low level clockwise curvature of the winds increasing the tornado threat.



Right now it appears the greatest threat of severe weather will be large hail. By looking at the forecast sounding for Tyler Friday afternoon, a lot of ingredients are coming together to produce large hail. There is a large amount of positive buoyant energy, CAPE, which will allow for robust updraft strength. There is also a cap in place, an area where the temperature increases above the earth’s surface holding back initial thunderstorm development. This will allow daytime heating to reach its peak before explosive thunderstorm development occurs. Also the sounding shows a large amount of the buoyant energy is in the hail growth region, between -10°C and -30°C. This tells me we will see some very large hail. When you combine this with strong wind shear, golfball size hail seems very likely with the possibility of baseball size hail occurring in a few storms.

Overall this does appear to be a significant severe weather threat. Both the hodographs and soundings are very similar to the event which occurred April 9th last year. If you don’t remember, this event produced 5 tornadoes in East Texas and 87 tornadoes across the Southern Plains and Southeast.

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