Torrential Rains Flood Cameron County from Brownsville to near San Benito, September 19th 2010

Rainfall so far September 17 through 22 (morning), 2010 across Deep South Texas (click to enlarge)

(T)raining and Flooding in Cameron County
4 to 7 inches Blitz Brownsville, Los Fresnos September 19th 2010

Overview
A series of rather vigorous upper level disturbances moved across the western Gulf of Mexico and into northeastern Mexico and the Rio Grande Valley between September 17th and 22nd. The disturbances acted on deep tropical moisture in place across the region and produced widespread, frequent showers and a few thunderstorms with locally torrential rainfall. While none of the activity was directly associated with Hurricane Karl, which made landfall near Veracruz early on the afternoon of Friday, September 17th, the broader circulation which birthed Karl was partly responsible for bringing the moisture into the western and northwestern Gulf. Total rainfall, as is typical with non–tropical–cyclone events during the summer and early autumn in the region, varied sharply. While Cameron, eastern Willacy, and much of Kenedy County shared 4 to 10 inches of rain during the period, the most densely populated part of the Rio Grande Valley – Hidalgo County – had less than 3 inches, with McAllen, Pharr, and Donna seeing less than an inch of rain.

The deep moisture struck jackpot for torrential rains and dangerous flooding early on September 19th, when upper level atmospheric energy combined with lower level converging air (and possible nocturnal low level jet of extremely moisture laden air from the Gulf). This synergy produced a prolonged band of torrential rains in the area of the peak convergence, just inland from the Gulf and covering south central Cameron County roughly between 3 AM and 8 AM, before the area pushed off to the east and northeast between 8 and 9 AM CDT (below). Between 5 and 7 inches of rain fell from Brownsville to near San Benito, creating extensive flooding in the area including impacting perhaps 100 or more structures, particularly in poorly draining areas.

Much of the flooding in Brownsville was the result of a domino effect from most resacas being filled, causing a general backup in the normal drainage flow from the resacas to the city water treatment plant and beyond. The slowed drainage left some areas with high water several days after the main event.

Impacts
While it is too early to calculate property loss of structures and vehicles due to the flooding, it is likely that it will total in the millions of dollars for Cameron County alone. These values will be tacked on to damage from Hermine, mainly from wind, earlier this month. Needless to say, it will be a September to remember in parts of the Lower Rio Grande Valley. The following are flood reports from the events of September 19th. October 5th Update: Adjusted numbers and locations of residential damage in Brownsville

35 homes with water incursion in Colonia Galaxia in West Brownsville along Military Highway, and Tradition Estates northwest of the Paredes Line/Alton Gloor intersection.
Water into yards in Quail Hollow, between Ruben Torres and Alton Gloor, (west side of town), and into yards along the Emerald Valley resaca
Thirty-seven residents evacuated from 9 flooded homes in Laureles (2.5 miles northwest of Los Fresnos)
Several homes impacted in the Green Valley Farms area along FM 510 near San Benito. At one location, 17 small mixed breed dogs were rescued from 2 or more feet of water which had flooded their kennels.
Paredes Line Road covered with up to 2 feet of water between Paseo Plaza and the T–Mobile Offices (just north of Ruben Torres to CSR Road, including the area around the Brownsville Events Center)
Sections of the right lane of southbound FM 511 under water between Alton Gloor and the Port of Brownsville
FM 1575 closed near/at State Road 100 in Los Fresnos.
High water at intersection of Palm Boulevard and Levee Street in Brownsville
Flooding along Boca Chica Boulevard between McDavitt and Security in Brownsville
At least 2 feet of standing water along Expressway 77 Frontage Road near Price Road
Flooding along International Boulevard at 14th Street in Brownsville
Parts of State Highway 100 were under water, as well as sections of FM 803 near Los Fresnos
Parts of State Highway 345 between San Benito and Rio Hondo were flooded; intersection with FM 106 also covered with high water

Thanks to City of Brownsville Emergency Management, Cameron County Emergency Management, and The Brownsville Herald for many of the reports listed here.

In addition to the heavy rains, persistent fetch of moderate east winds maintained dangerous rip currents across the beaches of South Padre Island through the weekend of September 18th and 19th and into the 20th, along with high surf. Tides ran 1 to 1.3 feet above predicted, including exceeding 2.5 feet at Port Isabel on the 19th (2.59 feet at 330 AM CDT). Tidal run–up reached just below the dune lines, but likely shut down the county beach access points to vehicular traffic during the period. As of this writing, there were no injuries or fatalities due to the active surf and high tides.

Rainfall Text Table

 
PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1242 PM CDT THU SEP 23 2010

...PRELIMINARY FINAL RAINFALL SEPTEMBER 17TH THROUGH 22ND...

UPDATED...INCLUDES DATA RECORDED DURING THE MORNING OF SEPTEMBER 23RD.

THE FOLLOWING ARE PRELIMINARY RAINFALL TOTALS DURING THE PERIOD OF
SEPTEMBER 17TH THROUGH 22ND...WHEN DEEP TROPICAL MOISTURE ASSOCIATED
WITH A SERIES OF UPPER LEVEL DISTURBANCES MOVED ACROSS
DEEP SOUTH TEXAS AND PRODUCED SEVERAL INCHES OF RAINFALL.

IN THE TABLE BELOW...INFORMATION THAT FOLLOWS THE LOCATION NAME...FOR
EXAMPLE BROWNSVILLE 4.2 NE...INDICATES DISTANCE IN MILES AND COMPASS
DIRECTION FROM THE CENTER POINT OF THE CITY OR TOWN.

NOTES: BROWNSVILLE/SOUTH PADRE INTERNATIONAL AIRPORT SHATTERED
ITS PREVIOUS RECORD FOR SEPTEMBER 19TH. UNOFFICIALLY...6.48
INCHES FELL WHICH WAS 1.24 INCHES ABOVE THE PRIOR RECORD OF 5.24
INCHES FOR THE DATE.

FOR SEPTEMBER 2010 THUS FAR...BROWNSVILLE/SOUTH PADRE INTERNATIONAL
AIRPORT HAS EXCEEDED 10 INCHES AND IS NOW UNOFFICIALLY AT 12.32
INCHES...WHICH RANKS UNOFFICIALLY AS THE 10TH WETTEST SEPTEMBER
ALL TIME...SINCE RECORDS BEGAN IN THE LATE 19TH CENTURY. IT LOOKS
NEARLY CERTAIN THAT BROWNSVILLE WILL RISE FARTHER UP THE CHART
WITH MORE RAIN TO COME BEFORE MONTH`S END.

REACHING NUMBER ONE IS VERY UNLIKELY. IN 1886...A WHOPPING 30.57
INCHES FELL IN SEPTEMBER...MAKING IT THE ALL TIME WETTEST MONTH IN
RECORDED HISTORY AT BROWNSVILLE.


LOCATION              COUNTY      RAINFALL  OBS TYPE  REMARKS


BROWNSVILLE 4.2 NE    CAMERON    10.26      COCORAHS  THRU 900 AM 9/22*
BROWNSVILLE 4.4 NE    CAMERON     9.91      COCORAHS  THRU 900 AM 9/22
BROWNSVILLE 4.1 E     CAMERON     9.40      COCORAHS  THRU 900 AM 9/23
BROWNSVILLE 4.9 NW    CAMERON     9.39      COCORAHS  THRU 900 AM 9/23
BROWNSVILLE 0.1 SSE   CAMERON     9.17      COCORAHS  THRU 900 AM 9/23
BROWNSVILLE/SPI ARPT  CAMERON     8.81      ASOS      THRU 900 AM 9/23
BROWNSVILLE 3.5 N     CAMERON     8.56      COCORAHS  THRU 900 AM 9/23
LOS FRESNOS 0.3 E     CAMERON     8.50      COCORAHS  THRU 900 AM 9/23
BROWNSVILLE 5.0 NNW   CAMERON     8.35      COCORAHS  THRU 900 AM 9/23
BROWNSVILLE 2.2 W     CAMERON     8.29      COCORAHS  THRU 900 AM 9/23
SOUTH PADRE ISLAND    CAMERON     7.83      MESONET   THRU 900 AM 9/23
RANCHO VIEJO 0.7 E    CAMERON     7.61      COCORAHS  THRU 900 AM 9/23
BROWNSVILLE 0.9 SW    CAMERON     7.17      COCORAHS  THRU 900 AM 9/21
HARLINGEN 2.6 ESE     CAMERON     6.99      COCORAHS  THRU 900 AM 9/23
BROWNSVILLE 0.8 NNW   CAMERON     6.88      COCORAHS  THRU 900 AM 9/22*
RANCHO VIEJO 3.0 SE   CAMERON     6.84      COCORAHS  THRU 900 AM 9/20
LINN/SAN MANUEL NWR   HIDALGO     6.88      MESOWEST  THRU 900 AM 9/23
FALFURRIAS            BROOKS      7.68      COOP      THRU 700 AM 9/23
LAGUNA ATASCOSA NWR   CAMERON     6.35      MESOWEST  THRU 900 AM 9/23
BAYVIEW/ARPT          CAMERON     6.30      ASOS      THRU 900 AM 9/23
SAN MANUEL            HIDALGO     5.96      COOP      THRU 900 AM 9/23
SAN BENITO 5.0 SSE    CAMERON     5.74      COCORAHS  THRU 900 AM 9/23
HEBBRONVILLE          JIM HOGG    5.32      COOP      THRU 815 AM 9/23
ARMSTRONG             KENEDY      5.26      COOP      THRU 645 AM 9/23
SARITA 7 E            KENEDY      5.25      COOP      THRU 800 AM 9/23
HARLINGEN             CAMERON     5.04      COOP      THRU 800 AM 9/23
RIO HONDO 9.4 NE      CAMERON     4.88      COCORAHS  THRU 900 AM 9/21
PALM VALLEY 2.2 SSW   CAMERON     4.50      COCORAHS  THRU 900 AM 9/23*
HARLINGEN 3.3 WSW     CAMERON     4.14      MESONET   THRU 900 AM 9/22
HARLINGEN 4.7 WSW     CAMERON     4.13      COCORAHS  THRU 900 AM 9/20
HARLINGEN 4.3 WSW     CAMERON     4.11      COCORAHS  THRU 900 AM 9/23*
FALCON LAKE           STARR       4.04      MESOWEST  THRU 900 AM 9/23
MERCEDES              HIDALGO     3.80      COOP      THRU 700 AM 9/23
HARLINGEN/VIA         CAMERON     3.70      ASOS      THRU 900 AM 9/23
LA JOYA 11.1 N        HIDALGO     3.60      COCORAHS  THRU 900 AM 9/23
RIO GRANDE CITY       STARR       3.11      COOP      THRU 715 AM 9/23
EDINBURG 1.1 WSW      HIDALGO     2.64      COCORAHS  THRU 900 AM 9/22
RAYMONDVILLE          WILLACY     2.57      COOP      THRU 730 AM 9/23
LA JOYA               HIDALGO     2.56      COOP      THRU 615 AM 9/23
FALCON DAM            STARR       2.05      COOP      THRU 830 AM 9/23
ALAMO 1.5 NNE         HIDALGO     1.88      COCORAHS  THRU 900 AM 9/23
SANTA ANA NWR         HIDALGO     0.90      MESOWEST  THRU 900 AM 9/23
MCALLEN/MILLER        HIDALGO     0.72      ASOS      THRU 900 AM 9/23
MCALLEN 1.7 SSE       HIDALGO     0.60      COCORAHS  THRU 900 AM 9/22
MCALLEN               HIDALGO     0.33      COOP      THRU 700 AM 9/23

*DATA INCOMPLETE.

Radar animation of composite reflectivity, September 19th 2010 from 230 AM until 9 AM CDT

Loop of composite reflectivity, 230 AM until 9 AM CDT, September 19th. Note repeating, or "training" red and maroon echoes along and just east of the Federal Highway 77 corridor between Brownsville and San Benito for most of the period.