Friday, January 4, 2013

Potent Storm to Bring Heavy Rain / Severe Weather Threat Early Next Week...

I made a quick post on facebook the day before yesterday concerning the potential for severe weather across portions of Texas and the Deep South next week.  While some differences still exist (mainly with respect to the exact timing of the event), computer forecast models are slowly coming into agreement that one or more significant rainfall and severe weather events are likely in association with this system.

The storm system in question is currently located over the Pacific Ocean, to the South of Alaska, as indicated by the yellow circled area on the water vapor satellite image below:

The system is forecast to dive Southeastward this weekend, with the center expected to be in the vicinity of Las Vegas by 6am CST on Monday morning:

From that point forward is where some differences come about with respect to the handling of this system by the computer forecast models.  The European Model (which happens to be the one shown in the image above) continues to bring the system to the Southeast before turning it Eastward as a well organized storm as shown at 6am CST on Tuesday and Wednesday, respectively, on the next two images:

Meanwhile, the U.S. based GFS model turns the system to the East and then Northeast in a much more rapid fashion.  The images below are also valid at 6am CST on Tuesday and Wednesday, respectively, from that particular model:

It is noteworthy that the last few runs of the GFS model have started to move more in the direction of the European model, carrying the system gradually further to the South and slower (as well as better organized).  It will be interesting to see if that trend continues in the upcoming runs today and tomorrow (I suspect that it will).

If we take a compromise between the two models, which I think is the best approach at this time, then we are faced with a scenario under which both heavy rainfall and severe thunderstorms are likely to take place across portions of southcentral and southeastern Texas during the day on Tuesday of next week.  The threat would likely initiate near the I-35 corridor (including the Austin and San Antonio areas), and then spread Eastward (including the Houston Metro area) during the afternoon and evening hours:

Please keep in mind that the above threat map is based on the "compromise" solution between the two major computer models as described above.  There is still some question as to the exact timing and track of this event, so be sure to check back for updates over the coming days.

Regardless of your "model of choice", the scenario depicted above (and particularly the one shown by the European model) is very similar to one that produced a severe weather event along the I-35 corridor from Austin to San Antonio during the pre-dawn hours of January 25, 2012.  Residents of the region will probably remember that as an event that resulted in widespread, heavy rainfall, locally damaging wind gusts, as well as a tornado that touched down in northeast Austin.

While it is still a bit too early to tell whether or not a similar situation will take place next week, there is increasing confidence that a locally heavy rainfall and severe weather event is likely across much of the same general area, so folks in this region should monitor the weather closely for the latest information.

While the prospects of severe weather are not particularly attractive to most folks across the region, the potential for a widespread, beneficial rain event is certainly welcome news.  Computer forecast models are suggesting that 1-2 inches of rain will fall on a widespread basis, with locally heavier amounts possible:

Keep in mind that the rainfall forecast map above, generated by the National Weather Service for the period 6am Monday to 6am CST Wednesday of next week leans more heavily toward the GFS model solution.  If the European model solution (or even our compromise proposed above) verifies, then the heavy rain band will extend further to the South/Southwest in Texas.

The threat of severe weather and locally heavy rainfall will shift Eastward into portions of the Deep South and Mississippi Valley region on Wednesday and into Thursday.  Just how far North and East will depend on whether the slower, further South European model solution or the faster, further North GFS model solution (or a compromise between the two) comes to pass.

"Stay tuned" for more information on this developing weather situation over the coming days.  If you live in the threat areas described above, it wouldn't be a bad idea to take a few moments this weekend to check out your severe weather safety kit and make sure that you are ready in case threatening weather affects your area next week.

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