Wednesday, October 21, 2009
Heavy Rain/Storms Possible Tonight
The above image shows the forecast rainfall for the next 48 hours. With plenty of lift and moisture in place, heavy rain appears likely overnight tonight into tomorrow morning. Because of this, most areas north of I-20 in East Texas are under a flash flood watch.
Another concern, although it is very small, is that there is a chance of mini supercells across the region tonight into tomorrow morning. A mini supper cells have mini characteristics of a classic supercell but on a much smaller scale. A few of the storms tonight have been showing signs of low level rotation indicating a mini mesocyclone, hence, a mini supercell.
Below are a few images of the forecast across East Texas at 7AM tomorrow. The 1st image is of the lifted index. Any value below 0 shows there is buoyant surface are that could lead to surface based convection. LIs around East Texas are in the -2 range tomorrow morning.
The second image shows the amount of SBCAPE, or energy available for thunderstorm updrafts. The values are very low, less than 500 in most areas. However, most of this CAPE if found in the lowest layer of the atmosphere which will be encountering lots of spin. This will help lead to a few storms having low level mesocyclones. The image below the SBCAPE shows the amount of CAPE between 0-3km. This low level CAPE is enough to help in tornadogenesis.
The next image shows the amount of 0-1km SRH in the atmosphere. This value is approaching 200 over much of East Texas. Again, this value would allow for tornadoes to develop.
The chances of a tornado developing tonight is less than 2% this evening and overnight but, we will have to watch the storms closely.