Click for Animation of radar base velocity from strong to severe thunderstorms racing across the Rio Grande Valley, May 18, 2010
Click image for base velocity animation across the Lower Rio Grande Valley, from 9 until 1015 AM CDT May 18th 2010.

Whoomp! (There it Was)
Wind Damage, Hail, Flooding Rattle Valley May 18th

Overview
The combination of upper level energy, overnight remains of outflow boundaries from storms near the Lower Rio Grande River, and the approach of thunderstorms from south Texas toward the Rio Grande Highlands with a very unstable atmosphere intensified these storms into a mesoscale convective system which raced through the Rio Grande Valley between 8 AM and 1045 AM, producing urban flooding, minor wind damage, pockets of large hail, and frequent cloud to ground lightning. An earlier cluster of storms east of the Port Isabel/Laguna Vista area may have produced a brief "landspout" tornado. A visible satellite photo shows the scope of the thunderstorm system.

The squall line ripped into McAllen a little before 8:30 AM, producing blinding, wind driven rain which piled up to a new May 18th record of 2.82 inches in a little more than an hour at Miller International Airport, with local reports suggesting heavier rain near the center of town just a few miles north. Urban to locally Flash Flooding was reported between Mission and McAllen; a local resident witnessed high water at 10th Street and Pecan Avenue. As the system tracked east, energy from the unstable atmosphere continued to maintain its intensity while increasing momentum accelerated some of the cells’ movements. One of these developed a 50 to 60+ mph wind core, which raced from Harlingen/San Benito eastward to South Padre Island. Along and near the wind core, hundreds of tree limbs were snapped, power lines fell, and even a catamaran was flipped on South Padre Island.

Total rainfall ranged from 2 to at least 3 inches in the Mission and McAllen area, with nearly 4 inches at the Cameron County Airport in Bayview. Unofficially, 1.32 inches fell at Brownsville/South Padre Island International Airport, 0.80 inches fell at Valley International Airport in Harlingen, and 3.58 inches fell at Cameron County Airport in Bayview.

A summary of reports received thus far follows:

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE BROWNSVILLE TX
656 PM CDT WED MAY 19 2010
 
..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..
 
0724 AM     MARINE TSTM WIND 7 N LAGUNA VISTA        26.20N 97.29W
05/18/2010  M45.00 MPH       GMZ130             TX   C-MAN STATION
 
            45MPH WIND GUST RECORDED OFF REALITOS PENINSULA. TIME IS
            APPROX DUE TO STATION REPORTING INTERVALS.
 
0812 AM     MARINE TSTM WIND 7 N LAGUNA VISTA        26.20N 97.29W
05/18/2010  M56.00 MPH       GMZ130             TX   C-MAN STATION
 
            STATION OFF REALITOS PENINSULA RECORDED 56MPH WIND GUST.
            TIME IS APPROX DUE TO STATION REPORTING INTERVALS.
            
0825 AM     HAIL             MCALLEN                 26.22N 98.24W
05/18/2010  M1.50 INCH       HIDALGO            TX   EMERGENCY MNGR
 
            OCCURRED AT LA QUINTA INN ON SOUTH 10TH STREET.           
 
0841 AM     TORNADO          PORT ISABEL             26.07N 97.22W
05/18/2010                   CAMERON            TX   NWS EMPLOYEE
 
            NWS EMPLOYEE FROM CENTRAL REGION REPORTED THAT A
            WATERSPOUT MOVED ONSHORE NEAR PORT ISABEL.
 
0842 AM     FUNNEL CLOUD     EDINBURG                26.30N 98.16W
05/18/2010                   HIDALGO            TX   PUBLIC
 
0845 AM     HAIL             4 E EDINBURG            26.30N 98.10W
05/18/2010  E0.88 INCH       HIDALGO            TX   PUBLIC
 
            NICKEL SIZE HAIL IN SAN CARLOS.
 
0855 AM     TSTM WND DMG     EDCOUCH                 26.29N 97.96W
05/18/2010                   HIDALGO            TX   BROADCAST MEDIA
 
            ROOF OF MOBILE HOME BLOWN OFF. TIME OF EVENT IS A ROUGH
            ESTIMATE.
 
0900 AM     FLASH FLOOD      MISSION                 26.21N 98.32W
05/18/2010                   HIDALGO            TX   FIRE DEPT/RESCUE
 
            MISSION FIRE DEPARTMENT REPORTED SEVERAL ROADS THROUGHOUT
            MISSION UNDER 2 TO 3 FEET OF WATER.
 
0906 AM     FUNNEL CLOUD     2 W WESLACO             26.16N 98.02W
05/18/2010                   HIDALGO            TX   EMERGENCY MNGR
 
            EM REPORTED FUNNEL CLOUD ON WEST SIDE OF WESLACO NEAR
            WESTGATE DRIVE.
 
0915 AM     FLASH FLOOD      MCALLEN                 26.22N 98.24W
05/18/2010                   HIDALGO            TX   DEPT OF HIGHWAYS
 
            CITY TRANSPORTATION DEPARTMENT REPORTED 7 TO 9 CARS
            STALLED IN FLOOD WATERS HALFWAY UP TO CAR DOORS AT 10TH
            STREET AND PECAN IN MCALLEN.
 
0920 AM     TSTM WND DMG     WESLACO                 26.16N 97.98W
05/18/2010                   HIDALGO            TX   EMERGENCY MNGR
 
            POWER LINES DOWN IN WESLACO, PER EMERGENCY MANAGEMENT.
            TIME OF REPORT IS TIME CALL WAS RECEIVED.
 
0925 AM     TSTM WND DMG     RAYMONDVILLE            26.48N 97.78W
05/18/2010                   WILLACY            TX   COUNTY OFFICIAL
 
            TREES BLOWN DOWN ON VARIOUS STREETS ACROSS RAYMONDVILLE.
            REPORT IS FROM CITY HALL AND TIME IS APPROX.
 
0934 AM     TSTM WND GST     HARLINGEN               26.20N 97.69W
05/18/2010  M60.00 MPH       CAMERON            TX   ASOS
 
0935 AM     TSTM WND GST     SAN BENITO              26.14N 97.64W
05/18/2010  E60.00 MPH       CAMERON            TX   PUBLIC
 
1015 AM     TSTM WND DMG     BROWNSVILLE             25.93N 97.48W
05/18/2010                   CAMERON            TX   NEWSPAPER
 
            LOCALLY RENOWN 20 YR OLD COTTONWOOD TREE BLOWN DOWN AT
            EAST LEVEE AND 10TH STREET. TIME IS APPROX.
 
1030 AM     TSTM WND DMG     PORT ISABEL             26.07N 97.22W
05/18/2010                   CAMERON            TX   LAW ENFORCEMENT
 
            POWERLINES AND POWER POLES BLOWN DOWN IN SEVERAL
            LOCATIONS THROUGHOUT PORT ISABEL.
 
1030 AM     TSTM WND DMG     SOUTH PADRE ISLAND      26.08N 97.18W
05/18/2010                   CAMERON            TX   LAW ENFORCEMENT
 
            POWER LINES AND TRANSFORMER BLOWN DOWN AT INTERSECTION OF
            CONTELLATION DR AND LAGUNA BLVD.
 
1030 AM     TSTM WND DMG     3 N SOUTH PADRE ISLAND  26.12N 97.18W
05/18/2010                   CAMERON            TX   EMERGENCY MNGR
 
            PALM TREES BLOWN DOWN ON CORA LEE. ALSO HAD LARGE METAL
            SIGNS BLOWN OFF OF THE QUEEN ISABELLA CAUSEWAY BUT LANDED
            ON THE BRIDGE. TIME IS APPROX.
 
1036 AM     MARINE TSTM WIND 1 WSW SOUTH PADRE ISLAN 26.07N 97.19W
05/18/2010  M64.00 MPH       GMZ130             TX   COAST GUARD
 
            COAST GUARD STATION LOCATED ON SOUTH END OF SOUTH PADRE
            ISLAND RECORDED 64MPH WIND GUST ON SOUTHERN LAGUNA MADRE.
            TIME OF EVENT IS APPROX DUE TO STATION REPORTING
            INTERVALS.
 
1037 AM     TSTM WND GST     2 N SOUTH PADRE ISLAND  26.11N 97.18W
05/18/2010  M60.00 MPH       CAMERON            TX   PUBLIC
 
            60MPH WIND GUST RECORDED ON SHEEPSHEAD STREET FROM
            CW4827 VIA CITIZEN WEATHER OBSERVER PROGRAM.
Click for Animation of radar base reflectivity from strong to severe thunderstorms racing across the Rio Grande Valley, May 18, 2010
Click image for base reflectivity animation across the Middle and Lower Rio Grande Valley, from 805 until 1015 AM CDT May 18th 2010.

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