Flash Flood — Cameron, Texas

2018-06-20 · near Brownsville, Cameron, Texas

Event narrative

One day after 3 to more than 5 inches fell between Brownsville and Los Fresnos during the afternoon and early evening hours, a repeat event occurred, fed by deep tropical moisture and multiple boundaries left behind from devastating morning flooding across western Cameron and eastern Hidalgo County. A persistent line of torrential rainfall dominated through the early evening commute, with another 3 to 6 inches having fallen for a two-day total of 6 to 11+ inches. The second day rainfall produced more widespread flooding across locations in and east of Brownsville and Los Fresnos, with farm and subdivisions under 2 to 3+ feet of water when all was said and done.

The additional flooding on saturated soils (pump priming from June 19) likely produced more damage this second go-round, including more erosion to drainage canals/ditches and mainly rural roads. Doubling of the damage left a total of around $20 million.

Wider weather episode

A broad tropical wave originating in the western Caribbean Sea moved across the Yucatan peninsula on June 15th and 16th, 2018. The slow moving but persistent system approached the Texas coast on Sunday, June 17th before finally arriving on June 18th. As the center axis of the wave passed the longitude of the coastline, the gates opened to repeated surges of tropical moisture deep into the atmosphere with origins in the western Caribbean Sea. A series of upper level disturbances interacted with this wave throughout its life cycle and helped to maintain a broad area of low pressure at all levels of the atmosphere for the period from June 18th through June 22nd across Rio Grande Valley, and the adjacent Gulf waters. Several surface-based boundaries and convergence along the coastline also aided the production of heavy rainfall. Individual convective systems spun in place at several points during the event, including:

*June 19 (Tuesday morning) in Brooks County

*June 19 (Tuesday afternoon) in Cameron County

*June 20 (Early Wednesday) in Hidalgo, Cameron, and Willacy County

*June 20 (Early afternoon) again in Cameron and Willacy County

*June 21 (Thursday morning) in Starr and Hidalgo County

*June 21 (Thursday afternoon) in Cameron, Willacy, and Kenedy County

*June 22 (Friday morning) in southwest Hidalgo and southern Starr County along the Rio Grande.

The wave and upper level disturbances finally exited southwest into north central Mexico on June 22nd, bringing a weekend of rain-free but oppressively hot and humid conditions to conduct broad recovery activity across the region.

In the larger population centers of Hidalgo County, as well as around Harlingen and Los Fresnos in Cameron County, between 12 and 18 inches of rainfall fell. Scenes of several feet of water that flooded thousands of vehicles, inundated several thousand homes and businesses with 18 inches to more than 3 feet of water, and hundreds of rescues of persons and pets were common. As of June 25, Emergency Declarations (state) were declared for Cameron, Hidalgo, and Willacy County.

As of mid August, the current statistics for the Hidalgo, Cameron, and Willacy portion of the affected area were as follows:

*More than 7,400 residences and businesses in Cameron and Willacy County with flood damage defined as minor to destructive by FEMA Standards.

*At least 20,000 residences and businesses considered affected by the floods. This includes the 7,400 listed above.

*More than 600 persons in at least ten shelters at the peak of the area-wide flooding

*Several thousand vehicles with varying degrees of flood damage

*Dozens to hundreds of roads, from neighborhood streets to major thoroughfares and frontage roads, closed during and after peak flooding

*More than 2,000 rescues from vehicles and homes were conducted

*21,000 meals served by the American Red Cross

*Public infrastructure damage estimated to be $50 million in Hidalgo and Willacy County alone

The breadth of the impact was greater than that of Hurricane Dolly in 2008, and for many in Hidalgo County, the rainfall totals ended up between Dolly's and Beulah's total.

View location on OpenStreetMap → (25.9201, -97.5385)

Source: NOAA Storm Events Database, event_id 807013. Narrative written by the NWS forecast office that issued the report.