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![]() Flooding of poor drainage areas in San Juan, Texas, after an estimated 3 to 4 inches of rain fell during the late afternoon of May 30, 2015. |
![]() "Lake NWS Brownsville" formed after more than two inches of rain fell in less than two hours during the late afternoon of May 31st, 2015 – a fitting bookend to a record–wet May. |
One Last (Rain) Dump Lower, Middle Rio Grande Valley Rains Close May 2015; Bring Record Totals to Some |
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May 29th: Morning Surprise! As the line neared the coast, the combination of the slowing momentum with convergence from light southeast flow cranked up the convection across eastern Cameron County between 930 and 1130 AM; the heaviest rainfall of the event brought 2.49 inches of soaking rain to east Brownsville (NWS office) and nearly 2 inches to Bayview. Minor flooding of poor drainage areas in Brownsville ensued. Equally, if not more, impressive than the rainfall was the rapid development of what is known as a "wake low" – an area of low pressure that sometimes follows the surge of high pressure than comes with sinking, cooler air in downdrafts and rain in the core of a strong thunderstorm. The low swung winds around to the east or southeast for about an hour near Brownsville, with peak winds cranking to 46 mph. The winds quickly shifted to the northwest behind an impressive roll cloud; the same winds continued for nearly two hours at South Padre Island, with frequent gusts over gale force (39 mph) which roughened surf and pushed water up to the dunes (below). Surface pressure fell five millibars, or 0.16 inches of mercury, with the passage of the low. ![]() 0.5° Base Velocity loop from 1125 AM to 125 PM May 29th 2015. Note the passage of the strong outbound velocity (red) which became strong inbound (green), all from the southeast, as the wake low (trough) passed by Brownsville. ![]() Rough surf running to the dune line on South Padre Island during the peak of the strong winds ahead of passage of a "wake low" behind strong thunderstorms in southeast Cameron County. Photo credit: https://spadre.com |
![]() 0.5° Base Reflectivity loop from around 6 PM through 8 PM CDT, May 30th 2015, showing development of heavy rain producing thunderstorm clusters from Hidalgo and Brooks County west through Starr, Zapata, and Jim Hogg County May 30th: Afternoon Soaker May 31st: Brownsville Blast Thus, May bookended a record month, and record spring, for much of the Rio Grande Valley/Deep South Texas Ranchland region, a record that was also shattered in Texas to much more dire results from rapid water flash flooding, which killed over two dozen during the latter half of the month. And, like a light switch, June would "flip the script" and begin dry, which allowed the Rio Grande Valley to finally begin drying out. |