April 24: Microburst Creates Midnight Mayhem for Colonia Residents in Donna and Weslaco

Photos taken from a National Weather Service and Emergency Management Survey after widespread wind damage struck the Donna/Weslaco area. Credit: National Weather Service Brownsville/Rio Grande Valley, NWS Brownsville/Rio Grande Valley social media followers, and others.
Stormy Weather: Microburst Slams Mid–Valley; Scores of Poorly Built Homes Impacted *April 24th Mayhem Rips Up Colonias, Removes Thousands of Ash Tree Limbs*
After a little more than two weeks of near–misses and being on edge for damaging thunderstorms (but plenty of rain and lightning), the atmosphere saved its "worst" for last. A small cluster of thunderstorms developed within a favorable zone for rapid updrafts over eastern Nuevo León State, Mexico, during the mid evening of April 24th. Unlike previous severe storms in April 2015, which produced similar wind damage and some hail across the Rio Grande Plains of Zapata and Jim Hogg County on April 12th and again on the 17th but weakened to mainly rain and lightning for the Valley, this small cluster moved at a steady clip – up to 40 mph at times –, into the easily lifted warmest and most humid low level air mass seen during the period. The result was an atmospheric bulldozer, crashing from the sky to the ground and racing to the northeast and east–northeast at speeds ranging from 65 to 80 mph. The initial cell likely produced large hail in Nuevo León before evolving into a straight–line wind event while crossing into Tamaulipas as it bent to the northeast just after 1030 PM local time. There was likely wind damage across the border from Pharr and Donna before the winds crashed across the river at the Lower Rio Grande Valley National Wildlife Refuge (Santa Ana). In only fifteen minutes, structural, tree, and powerline/power pole damage piled up from Alamo to Mercedes, extending north to pockets in Edinburg, Elsa, and Edcouch. The heaviest damage was noted in Donna and Weslaco, where a National Weather Service survey, joined by Emergency Management from Weslaco/Donna/Mercedes, Elsa/Edcouch, and Hidalgo County, determined peak winds ranged from 65 to 75 mph, with pockets of 80 mph speeds based on the type of damage, exposure, and construction. A second core of strong winds ripped through southwest Cameron County, with unknown tree damage in the Santa Maria/Los Indios area that continued northeast into the Harligen/Primera area before exiting near Rio Hondo. Rainfall was quick, but hard; locations on the core of the heaviest rain received between ½ and 1 inch.
Click on this map to open a .kmz file to display survey data from more than 20 points/photos in the Weslaco/Donna area damaged by microburst on April 24, 2015. Need Google Earth? Download here.	Preliminary local storm report map from Lower/Mid Valley microburst(s) of April 24, 2015. For full accessibility, including radar images, click here.
The following is a preliminary list of talking points from the April 24th microbursts. Preliminary local storm report(s) follow the velocity image loop below this section. An NWS and local Emergency Management team revealed peak winds ranging from 65 to 75 mph, with pockets of 80 mph, in the Weslaco/Donna area (below) Unofficially observed winds and corroborating damage suggested pockets of 60 to 72 mph in portions of Cameron and Willacy County, in the Santa Maria/Los Indios area northeast through Harlingen/San Benito to Rio Hondo. In Hidalgo County, damaging winds, perhaps between 75 and 80 mph, reached the Lower Rio Grande Valley National Wildlife Refuge at 11 PM CDT. The wind field reached Elsa/Edcouch at approximately 1120 PM CDT, and was weakening at the time. As of April 27, at least two dozen homes in colonias were destroyed (uninhabitable); at least five more were demolished. All of these structures were very poorly built and/or raised onto cinderblock but not anchored. It is likely that at least 100 residences across the Lower and Mid Valley had some degree of damage. There were no reported deaths or injuries. At least two large families fled their trailers shortly before the winds demolished them. Hundreds, if not more than a thousand, tree limbs were felled; dozens of trees were uprooted. The vast majority were Rio Grande Ash, known as a "Soft Hardwood" variety. Live oak and mesquite limbs were also felled but in much smaller numbers. Live oak and mesquite are known as "Hard Hardwoods" which likely made a difference in their survivability rate in the near hurricane force gusts. Damage estimates will eventually be made available. A large number, possibly a majority, of properties destroyed or demolished were not insured. As of April 27th, a very conservative estimate of $500 thousand could be made. This value is likely to rise substantially. The American Red Cross supported a shelter operation at Iglesia de Dios Linaje Escogido (Church) to provide a safe haven for displaced residents of the Aurora Valley Colonia, from April 25th through at least April 28th. AEP Texas reported 13,000 customers without power immediately after the storm. Total values from all providers were likely between 15 and 20 thousand from midnight April 25th through the early morning hours. Several hundred customers, mainly in the Donna/Weslaco area, remained without power through April 27th. Wind was the dominant culprit, with a combination of trees on lines, lines down, and leaning poles. At any one location, strongest winds lasted between three and five minutes. 0.5° Base Velocity loop from 1045 through 1142 PM CDT, April 24th 2015. Note core of very strong winds (light to medium blue) that cross the mid Valley. The colors indicated generally 60 to 75 mph (radar indicated) at 4500 to 5000 feet above ground; much of the wind reached the ground, causing the damage. Preliminary wind speed and quick impact graphic from April 24, 2015 microburst in southern Hidalgo County, Texas Below is the preliminary text storm report summary from April 24th, 2015. Note: Some times were adjusted based on survey results and radar estimates. PRELIMINARY LOCAL STORM REPORT...SUMMARY NATIONAL WEATHER SERVICE BROWNSVILLE TX 415 AM CDT SAT APR 25 2015 ..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON... ..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE.... ..REMARKS.. 1100 PM TSTM WND DMG DONNA 26.17N 98.05W 04/24/2015 HIDALGO TX LAW ENFORCEMENT HIDALGO COUNTY SO REPORTS MOBILE HOME FLIPPED OVER ON NOEMI STREET IN DONNA. 1100 PM TSTM WND DMG DONNA 26.17N 98.05W 04/24/2015 HIDALGO TX LAW ENFORCEMENT HIDALGO COUNTY SO REPORTS UNOCCUPIED CAR FLIPPED OVER BY STRONG WINDS AT THE SIOUX ROAD AND HUTTO ROAD INTERSECTION IN DONNA. 1100 PM TSTM WND DMG EDINBURG 26.30N 98.16W 04/24/2015 HIDALGO TX LAW ENFORCEMENT HIDALGO COUNTY SO REPORTS MOBILE HOME DAMAGE AT THE TOWER ROAD AND OWASSA ROAD INTERSECTION IN EDINBURG. 1100 PM TSTM WND DMG DONNA 26.17N 98.05W 04/24/2015 HIDALGO TX LAW ENFORCEMENT DONNA POLICE DEPARTMENT REPORTS MOBILE HOME FLIPPED OVER ON PONCIANO DRIVE JUST NORTH OF DONNA. 1100 PM TSTM WND DMG DONNA 26.17N 98.05W 04/24/2015 HIDALGO TX LAW ENFORCEMENT HIDALGO COUNTY SO REPORTS WIRE FENCE BLOWN DOWN ON MIRASOL ROAD IN DONNA. 1100 PM TSTM WND DMG DONNA 26.17N 98.05W 04/24/2015 HIDALGO TX LAW ENFORCEMENT DONNA POLICE DEPARTMENT REPORTS TREE AND UTILITY POLE DAMAGE ON NUMEROUS STREETS... INCLUDING SOUTH VICTORIA ROAD... MAIN STREET... HUTTO ROAD... AND VAL VERDE. 1100 PM TSTM WND DMG EDINBURG 26.30N 98.16W 04/24/2015 HIDALGO TX LAW ENFORCEMENT HIDALGO COUNTY SO REPORTS ALUMINUM FENCE BLOWN OVER ON OWASSA ROAD IN EDINBURG. 1118 PM TSTM WND GST WESLACO 26.16N 97.98W 04/24/2015 M72 MPH HIDALGO TX TRAINED SPOTTER TRAINED SPOTTER REPORTED 63 KT WIND GUSTS AT INTERSECTION OF 88TX AND MILE 1 1/2 ROAD.TIME ESTIMATED 1120 PM TSTM WND DMG 2 SE WESLACO 26.14N 97.96W 04/24/2015 HIDALGO TX EMERGENCY MNGR EMERGENCY MANAGER OF WESLACO REPORTED SEVERAL TREES DOWN IN THE PLEASANTVIEW AREA NEAR WESLACO. TIME ESTIMATED FROM RADAR. 1120 PM TSTM WND DMG LA FERIA 26.16N 97.82W 04/24/2015 CAMERON TX LAW ENFORCEMENT LA FERIA POLICE DEPARTMENT REPORTS TREE BLOWN DOWN ONTO PARKER ROAD IN LA FERIA. 1120 PM TSTM WND DMG 1 SW WESLACO 26.15N 98.00W 04/24/2015 HIDALGO TX PUBLIC PUBLIC REPORTED BACKYARD METAL PERGOLA DESTROYED ON THE SOUTHWEST SIDE OF WESLACO. TIME ESTIMATED FROM RADAR. 1125 PM TSTM WND DMG 2 E WESLACO 26.16N 97.95W 04/24/2015 HIDALGO TX BROADCAST MEDIA REPORT OF ROAD SIGNS BLOWN OUT OF THE GROUND ALONG US 83 NEAR WESLACO. 1125 PM TSTM WND DMG EDCOUCH 26.29N 97.96W 04/24/2015 HIDALGO TX LAW ENFORCEMENT SEVERAL POWERLINES DOWN IN THE CITY OF EDCOUCH. TIME ESTIMATED FROM RADAR. 1130 PM TSTM WND DMG LA FERIA 26.16N 97.82W 04/24/2015 CAMERON TX LAW ENFORCEMENT CAMERON COUNTY SO REPORTS 2 TREES DOWN ON FM 506 SOUTH OF CLARK ROAD IN LA FERIA. 1130 PM TSTM WND DMG PRIMERA 26.23N 97.76W 04/24/2015 CAMERON TX LAW ENFORCEMENT CAMERON COUNTY SO REPORTS UTILITY WIRES BLOWN DOWN INTO THE ROAD IN PRIMERA. 1130 PM TSTM WND DMG COMBES 26.24N 97.72W 04/24/2015 CAMERON TX LAW ENFORCEMENT CAMERON COUNTY SO REPORTS TREE BLOWN DOWN ONTO HAND ROAD IN COMBES. 1130 PM TSTM WND DMG HARLINGEN 26.20N 97.69W 04/24/2015 CAMERON TX LAW ENFORCEMENT HARLINGEN POLICE DEPARTMENT REPORTS TWO MEDIUM-SIZED TREES BLOWN DOWN ONTO GARRETT ROAD IN HARLINGEN. 1130 PM TSTM WND DMG SAN BENITO 26.14N 97.64W 04/24/2015 CAMERON TX LAW ENFORCEMENT SAN BENITO POLICE DEPARTMENT REPORTS 1 TREE BLOWN DOWN ONTO SOUTH SAM HOUSTON. ALSO TRAMPOLINE BLOWN INTO SIDE OF HOUSE THAT CAUSED WINDOWS TO BREAK ON SAN JACINTO DRIVE. ALSO DOWNED LIVE UTILITY WIRE AT INTERSECTION OF SOUTH DICK DOWLING AND ROWSEN AND ANOTHER LIVE WIRE DOWN ON ZILLOCK ROAD. ALL IN SAN BENITO. 1130 PM TSTM WND DMG MERCEDES 26.15N 97.92W 04/24/2015 HIDALGO TX LAW ENFORCEMENT MERCEDES POLICE DEPARTMENT REPORTS 10 TO 12 POWER LINES AND 15 TO 20 TREES DOWN ACROSS THE CITY OF MERCEDES. 1135 PM TSTM WND GST HARLINGEN VALLEY AIRPOR 26.23N 97.65W 04/24/2015 M58 MPH CAMERON TX ASOS HARLINGEN ASOS AT VALLEY INTERNATIONAL AIRPORT REPORTED A 58 MPH MEASURED WIND GUST. 1135 PM TSTM WND GST HARLINGEN 26.20N 97.69W 04/24/2015 M60 MPH CAMERON TX PUBLIC PUBLIC REPORTED A MEASURED 60 MPH WIND GUST WITH A DAVIS INSTRUMENT IN HARLINGEN. 1135 PM TSTM WND DMG PRIMERA 26.23N 97.76W 04/24/2015 CAMERON TX PUBLIC PUBLIC REPORTED MEDIUM SIZE TREE DOWN ON A CAR IN PRIMERA VIA SOCIAL MEDIA. 1137 PM HAIL LOS INDIOS 26.05N 97.75W 04/24/2015 E1.00 INCH CAMERON TX TRAINED SPOTTER TRAINED SKYWARN SPOTTER IN LOS INDIOS REPORTED QUARTER-SIZE HAIL.

Photo of satellite image of mesoscale convective system that ran into Starr County after midnight on April 24, 2015

Satellite photo with lightning overlaid of Mesoscale Convective System that dropped heavy rain in Starr County. The heaviest rain fell generally from 1230 to 130 AM. Click image for a full loop of the storm across the Upper Rio Grande Valley.

The Night Before: Thunderstorm Complex Soaks Starr County

The Rio Grande Valley was close to being hit by back–to–back significant impact weather on successive nights. During the evening of April 23rd, thunderstorms, some likely with large hail and damaging wind, formed in Nuevo Leóon. By midnight, the storms had weakened below severe limits (58 mph wind and 1 inch diameter hail) but organized into a Mesoscale Convective System (What’s a Mesoscale Convective System?) (MCS), typically more conducive to flooding in the Rio Grande Valley. Between 1230 and 130 AM on the 24th, 2 to 3 inches (estimated) of rain fell over and near Rio Grande City, flooding dozens of roads with up to a foot of flowing water as the rains began to subside. As the system punched northesat toward the South Texas Brush Country and Coastal Bend, the flood threat waned. Accompanying the rain was frequent cloud–to–ground lightning with hundreds of strikes in Starr County in a short time; several thousand customers in Starr and western Hidalgo lost power from the strikes.

Another threat developed after the rains ended. MCSs often produce a pressure couplet of small scale high pressure, where cold, dense air descended from the core of the rain and hail production area, and a "wake" low pressure area after the system passes. For the early April 24th MCS, the difference between high and low pressure increased across the Brooks and Kenedy County ranchlands, where southerly winds (with no rain) gusted to 35 to 40 mph, if not higher (Kingsville, in Kleberg County, briefly reached 50 mph). Strongest winds, including some damage, were reported across the South Texas Brush Country east to the Coastal Bend, including Corpus Christi. A report on these rare but notable impacts for South Texas north of the RGV is here.

There were benefits of this particular round of rain; the last sliver of Starr County not in "Exceptional Wetness" from the Standardized Precipitation Index in 2015 was now bumped up to the wettest category of the index (below), joining all but the South Padre Island beaches.

Standardized Precipitation Blend for the Valley and Deep South Texas on April 26, 2015