Monday, March 19, 2012
A Moderate Risk for Severe Storms Including Tornadoes Today
There is a moderate risk of severe thunderstorms across East Texas today including the threat of tornadoes. A very warm and moist air mass has set up across East Texas thanks to 7 days of a southeasterly flow off the Gulf of Mexico. Dew point temperatures are forecast to peak in the lower 70s ahead of a developing line of thunderstorms. The image below shows most of East Texas covered in yellow meaning dewpoints will be at least 65 degrees providing plenty of energy for thunderstorm development.
The latest High Resolution Rapid Refresh model breaks out a broken line of thunderstorms later this afternoon heading towards East Texas. This will be the first round of at least three lines of storms that develop.
The 0-6KM shear available across East Texas is more than enough for the storms that develop to become supercellular. Shear values will be approaching 50 to 60 knots across the area allowing mid level rotation to form with any storm that develops.
As these rotating thunderstorms move into East Texas they will be encountering low level helicity levels that are conducive for low level rotation which could lead to tornadogenesis. The image below shows areas of light green and yellow out ahead of the storms show low level helicity between 200 and 300 m^2/s^2.
The environment also shows large hail to be very possible across East Texas this afternoon and evening. The forecast soundings for both Forth Worth and Shreveport show large amounts of CAPE in the hail growth region. With the high shear levels, ice particles we be in the hail growth region longer making golfball to baseball size hail possible with the strongest storms.
One thing you will notice is the winds are more favorable for tornadoes the farther east you go. The good news is the farther east the storms move, the less forcing they will encounter so they may begin to weaken just a bit.
It does appear after the first round of storms moves through, more storms will develop throughout the night and into tomorrow morning. Before the rain ends Wednesday much of East Texas will receive between 3 and 6 inches of rain with a few areas picking up over 8 inches of rain.