A Wet Ending In Late August/Early September for South Texas

*Blog written on August 25, 2013 at 5:00am CDT*

Much of south Texas is dry and in some sort of drought (below image). The month of September is usually the “wettest” month of the year for much of the area, according to climatological data. However, deep south Texas will be seeing the potential for some good rain the last week and a half in August, and even through the beginning of September.


Drought Monitor as of August 20, 2013. The US Drought Monitor is updated weekly, every Tuesday and released every Thursday.

So just how much rain will deep south Texas be receiving over the next couple of weeks? That’s very hard to say. Rain and thunderstorms will occur on a daily basis over the next few days, but it will likely be hit and miss events. Here’s why:


0000z August 25, 2013 700mb analysis. Image courtesy: College of Dupage

An inverted trough is located over the western Gulf of Mexico and is slowly moving westward. This will provide tropical and subtropical moisture to form and move inland from the Gulf. Mid-level flow will be providing ample opportunity for showers and thunderstorms to form, especially during the heating of the day, and will help kick-start sea breezes along the Texas coast. As long as this pattern sticks around, subtropical and tropical moisture will continue to be fed into Texas coast.

Something else that might be contributing to rain and thunderstorms in south Texas will be a tropical wave (AL95) in the Bay of Campeche (shown below).  As of early morning, August 25, this tropical wave is not affecting south Texas much. However, there is a chance that some of its tropical moisture it produces may slide north and affect south Texas. This tropical wave is not forecast to strengthen much over the next 48 hours, but may develop into a weak tropical depression before making landfall around Veracruz, Mexico on Monday.  The less organized this storm is at landfall, the more rainfall south Texas will receive. I know that may sounds contrary to what you’re thinking, but the more organized this storm becomes, storms will be concentrated around the center and less likely to reach the Rio Grande Valley. Since mid-level flow won’t be changing much over the next 3-4 days, I expect showers and thunderstorms to flare up, whether directly or indirectly influenced from this tropical system.  And of course, there’s always the chance it may shift more north or south than what forecast models say.


IR satellite showing  Invest AL95 as of 0945UTC August 25, 2013.


As far as how much rain, here’s one model’s thinking of how much rain will be falling between now and 7 am Saturday, August 31.  As you can see, much of south Texas is expected anywhere from half an inch of rain, to just over an inch in some places, and locally heavier amounts possible. Again, this is one forecast model (one possible solution) of many.


00z August 25 ECMWF model showing total rainfall between late PM, Sunday, August 24 through early AM, Saturday, August 31, 2013. Image Courtesy: AccuWeather Pro. 


No matter how much rain is received over the next few weeks, south Texas will still likely be in a drought, since much of the area is about half a foot below normal.


About Brian

University of Oklahoma graduate with a degree in Meteorology. Follow me on Twitter: @WeatherInformer
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