The Weather Centre has issued a Tornado Watch for South Texas, effective from 5:00 PM this evening into 6:00 AM tomorrow morning, CST. This replaces the Level 2 Severe Thunderstorm Watch issued by our office this morning.
The Weather Centre
3:28 PM CST
January 24, 2012
After observing the latest NAM model forecasts, which are equipped with helicity forecasts, I have deemed it appropriate for a Level 1 Tornado Watch to be issued in place of the Level 2 Severe Thunderstorm Watch issued by our offices earlier today.
NAM Model now indicates the storm system will be digging further south into Texas, which may bring the biggest tornado threat further south than we have shown. However, do feel like all areas that needed to be encompassed in the watch are covered.
As an upper level disturbance moves into south Texas, we are already seeing showers and thunderstorms erupt from the Central Texas region, moving due north. Surface Analysis indicates 2000 j/kg of instability is already in place for the areas shaded in red above, providing a good environment for stronger storms to evolve. Additionally, helicity values as well as some supercell composites indicate a fair environment potential for some rotation in thunderstorms. Surface Analysis also indicates the rising potential for hail to fall, possibly significant, over the state of Texas.
Have high confidence in this watch and believe it is warranted. I do not believe an upgrade to level 2 is going to be necessary, which would indicate an occasional strong tornado is possible, while we are expecting only isolated tornadoes this evening.
May end up issuing a Level 1 severe thunderstorm watch for parts of north Central Texas, as well as the rest of southeast Texas in the event some thunderstorms develop in those areas, but confidence on that particular item is not exactly crystal clear.
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