RGV’s La Niña Conditions To Continue Into May

***For full, in depth facts and data, visit this site from the National Weather Service in Brownsville, TX***

     If you’re living in South Texas right now, you know that it has been hot, dry, and windy for a good amount of time now.  If you’re wondering when it will get cooler, when it will rain again, or when the winds will die down, then I’m here to tell you:  not anytime soon.  The best thing to hope for is a strong enough cold front to push through that brings down temperatures 5-10 degrees and some rain.  Even that, though, is starting to look like a long shot, as we enter the month of May.

     It’s becoming that time of year where most of the cold fronts are stalling or dissipating north of the Rio Grande Valley.  Sure, there may be one or two that have the strength to push on through, but 24-36 hours after the front passes, temperatures return into the lower to middle 90s.  So what’s to blame for this unusual dry spell over south Texas?

La Niña

    La Niña would be one thing to blame.  Rather than trying to fully explain what La Niña is and how it differs from El Niño, I will direct you to NOAA’s explanation of El Niño here, and La Niña here.  I apologize for the lack of explanation.

Below (figure 1) is a simple graphic from NOAA of the conditions of La Niña. Basically, warmer waters in the western Pacific Ocean is driving the jet stream in a way that the Rio Grande Valley receives above average temperatures and below average amounts of precipitation.

The big question that you are probably wondering is when will the effects of La Niña wear off? Well, it will start to neutralize towards the middle of May into early June, according to the NWS.  This means, hot, windy, rainless times will continue until then.  Granted, this doesn’t mean it can’t rain; there will be some periods of rain and calm winds (hopefully, fingers crossed).

Figure 1. General conditions for La Niña (warmer SST in western Pacific).

How Dry Has It Been?

***All data courtesy of the National Weather Service in Brownsville, Texas***

    Since October 1, 2010, Brownsville has received only 2.69″ of rain up until April 18, 2011.  This is their 2nd driest period on record during this time frame.  Rio Grande City has recorded only 1.37″ of rain during this time frame, the driest on record; McAllen, too, has broken a record with only 1.43″ since October 1st, 2010.  Below (figure 2) is a map of how much rainfall has fallen since October 1st, 2010 and how it ranks as far as driest period on record (rank in parenthesis).

Figure 2. Valley Drought. Rainfall amounts and city rank in dryness from October 1, 2010 to April 18, 2011. Image courtesy of NWS Brownsville.

      Figure 3 (below) shows the percent of normal precipitation from the period of October 1, 2010 through April 18, 2011.  Click image to enlarge.  Notice some spots of Starr and Hidalgo Counties are 5% of normal or less.

Figure 3. Percent of normal rainfall values from October 1st through April 18th. Courtesy of NWS Brownsville.

Edinburg’s 3-day Forecast

Figure 4. Edinburg's 3-day Forecast issued 4/22/2011

     Here is Edinburg’s 3-day forecast.  Temperatures will remain hot and winds will remain breezy.  I did take temperatures down a bit for Sunday as pressure gradient loosens just a tad.  Temperatures today (4/21) didn’t get as high as forecast, which is my second reasoning.  The winds on Monday won’t be as breezy and gusty as the previous days.  A cold front is forecast to move through the Valley on Wednesday, cooling temperatures down about 5-10 degrees for Thursday.  More on this as it approaches.

***A special thanks to the National Weather Service-Brownsville for all the hard work they do to protect the citizens of the Rio Grande Valley***


About Brian

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