Early November Deluge Dumps 2 to 4 inches or More in Bands Across the Rio Grande Valley

Rainfall map and observations, November 6-7 2013, Rio Grande Valley, Texas

Rainfall from the afternoon of November 6th through the morning of November 7th, 2013, across the Rio Grande Valley and Deep South Texas.

Early November 2013 Cold Front Brings Welcome Rainfall, Some Flooding
Some Valley Locations Received Several Inches While Others Had None

Event Summary
The combination of an approaching surface cold front, an upper level disturbance, sufficient atmospheric moisture, and a weak afternoon sea breeze triggered multiple bands or clusters of showers and thunderstorms from the afternoon of November 6th into the early morning of November 7th. Typical of systems with atmospheric convection, rainfall differences were highly localized, particularly in the sea breeze zone (image below) where locations just 15 miles apart had rainfall ranging from none to nearly 5 inches (above). For some, the single day – in some cases single hour – rainfall was four times the monthly average! November monthly averages range from 0.5" to 1.5" except 1 to 2" in southeast Cameron County.

In general, a band of 2 to 4+ inches fell along and just ahead of the front from the King Ranch through the ranches and farms of northern and western Hidalgo County filled several fields with water and likely caused nuisance flooding of local ranch roads. Most of this rain fell from mid to late afternoon through the late evening on the 6th, with lighter amounts following the front into the early morning of the 7th. The band slowly dissolved as it oozed into the Lower Valley, but was still able to drop up to an inch around Harlingen during a couple hours either side of midnight. Steady rains along the behind the front dropped a healthy 1 to 2 or so inches in Starr County; heaviest rainfall for the event (not shown) fell with thunderstorm clusters southwest of Reynosa (Tamaulipas, Mexico).

Loop of locally heavy rainfall across ranchlands from the King Ranch (southern Kenedy County) southwest to western and northern Hidalgo County between 6 and 730 PM, November 6th 2013. Click to enlarge.

Loop of locally torrential rains across southern Cameron County between 230 and 345 PM November 6th 2013. Nearly five inches of rain fell in West Brownsville during this time, causing local flash flooding.

Prior to significant development of the pre frontal band across the mid Valley and King Ranch area, a weak sea breeze enhanced lift along and east of the Highway 77/Interstate 69E corridor between San Benito and Brownsville a little after 2 PM. By 230 PM, blinding rain engulfed Farm to Market 511, State Route 100, and other locations between Los Fresnos and north Brownsville. The storm developed/crept slowly, edging into the core of Brownsville for more than an hour before gradually drifting southwest into northeastern Tamaulipas (above). In 90 minutes or less, between 2 and just under 5 inches fell from Los Fresnos through west Brownsville. Numerous instances of flooding, some life threatening, quickly ensued:

4.23 to 4.96 inches pushed water "up to the windshield" of at least one vehicle on W. Washington Street
Preliminary reports suggested "several businesses that had some water in them in west Brownsville
Numerous thoroughfares had several inches to nearly 2 feet of water on them across the business district, limiting travel
Some resacas reached bankful or flooded low lying grassy areas
During the peak of the rains, 42 streets had flooding that reduced travel to one lane or less

As the core of Brownsville and the extended frontage business district experienced flooding, locations less than 10 miles to the east, including Brownsville/South Padre International Airport (0.12 inches), had minimal rain; farther east, Port Isabel and South Padre Island were dry.

Weather setup for locally torrential rains across the Rio Grande Valley on November 6 2013 (click to enlarge)

The weather setup for the locally heavy rainfall on November 6th. Cold front drifting south combined with atmospheric moisture in place and a upper level disturbance (shear zone) to produce primary rain area (dark green band) from mid afternoon through late evening; in Cameron County, a weak early afternoon sea breeze aided rapid development of torrential rains near Brownsville (light green).

Point rainfall totals in the City of Brownsville (from Community Collaborative Rain Hail and Snow Network, CoCoRaHS). Green shaded area depicts area of heaviest rainfall and worst flooding.

Photo of street flooding just after rains ended near downtown Brownsville, between 4 and 5 PM on November 6, 2013. Courtesy of the City of Brownsville.

Preliminary Significant Rain Totals, November 6 through November 7, 6 AM to 9 AM CST
City/Town	County	Rainfall (inches)
Brownsville 2.2 West	Cameron	4.96
Brownsville 3.5 North	Cameron	4.66
Brownsville 1.5 West Northwest	Cameron	4.23
Brownsville 2.2 West Northwest	Cameron	3.77
La Joya 11.1 North	Hidalgo	3.75
McCook	Hidalgo	2.65
Armstrong	Kenedy	2.42
Sarita 7 East	Kenedy	2.40
Brownsville 1 North	Cameron	2.41
Los Fresnos 0.8 East Southesat	Cameron	2.40
Brownsville 5.0 North Northwest	Cameron	2.33
Brownsville 2.9 North Northeast	Cameron	2.26
Brownsville 4.9 Northwest	Cameron	2.21
Brownsville 0.1 South Southeast	Cameron	2.01
San Manuel/Cooperative	Hidalgo	2
La Joya	Hidalgo	2
Linn 8.4 West Northwest	Hidalgo	1.92
Los Fresnos 0.3 Northeast	Cameron	1.91
San Benito 0.6 South Southeast	Cameron	1.73
Rio Grande City 17.7 Northeast	Starr	1.70
Brownsville 1.7 North Northeast	Cameron	1.55
Brownsville 6.4 West Northwest	Cameron	1.53
Rio Grande City 13.8 North Northwest	Starr	1.50
Harlingen 2.6 East Southeast	Cameron	1.25
Harlingen/Valley Airport	Cameron	1.13
Rio Grande City/Cooperative	Starr	1
Weslaco/Cooperative	Hidalgo	1
Brownsville 4.1 East Northeast	Cameron	0.99
Falcon Dam	Starr	0.92
McAllen/Cooperative	Hidalgo	0.91
Mission 1.9 East Northeast	Hidalgo	0.90
Harlingen/Cooperative	Cameron	0.85
Rancho Viejo 0.7 East	Cameron	0.82
Santa Rosa	Cameron	0.82
Hebbronville	Jim Hogg	0.82
Alamo 1.5 North Northeast	Hidalgo	0.78
McAllen/Miller Airport	Hidalgo	0.74
Edinburg/Cooperative	Hidalgo	0.70
Port Mansfield	Willacy	0.15
Brownsville/SPI Int'l Airport	Cameron	0.12