Flash Flood — Hidalgo, Texas
2018-06-21 · near Abram, Hidalgo, Texas
Event narrative
State and local emergency management officials, as well as ground truth rainfall totals, reported widespread flooding in south-central Hidalgo County, focused on the Mission/Alton/West McAllen area as a firehose of thunderstorms persisted for more than five hours through the morning commute until around noon before finally dissipating. Estimated and measured rainfall for the event ranged from 6 to 11 inches, with periods of 2 to 3 inches per hour embedded during the heart of the morning commute. Numerous roads, thousands of homes and vehicles (specific number unknown) were under a range of water depth, ranging from 18 inches to 3 to 4 feet in either poorly draining neighborhoods from the west half of McAllen through Mission.
A peak total rainfall of 18.31 inches fell in Mission for the combined events of June 20-22. Estimated damage, using a combination of county-reported damage and standard doubling, was an estimated $22 million for this particular event. Actual values may be much higher as data continues to come in throughout 2019.
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 → (26.1699, -98.3890)
Source: NOAA Storm Events Database, event_id 807019. Narrative written by the NWS forecast office that issued the report.