Flash Flood — Cameron, Texas
2020-07-25 to 2020-07-26 · near Santa Rosa, Cameron, Texas
Event narrative
Afternoon and early evening rains of 2 to 3 inches fell across the IH-2 corridor of Cameron County, from La Feria to east of Harlingen, and saturated soils ahead of the torrential rains that were to come later in the evening as the southern and eastern eyewall pulled copious tropical moisture into northern Cameron County after sunset. Estimated rainfall of 4 to 6+ inches by mid evening began to produce known flash flooding in La Feria and Harlingen, with two water rescues conducted in La Feria just after 10 PM CST. Despite lighter rains, flash flooding would continue due to poor drainage situations, especially in the La Feria/Santa Rosa area. A broad south to north feeder band added another 2 to 4+ inches of rainfall to the storm totals during the pre-dawn hours, and light rains would continue to around noon in western Cameron County before ending. Note: Estimated flood-related public assistance property damage is provided in this episode. However, the total damage would also include another 3 to 5 inches that would fall in an unrelated tropical band of torrential rain during the evening of July 27th.
Flooding would decimate the cotton (lint) crop and other unharvested dryland crops to an estimated value of $27.1 million. Public assistance property damage as of this writing from flooding rainfall was estimated to be at $3.3 million. Additional public and individual assistance dollar damages, as well as insured damages, from flood waters was calculated using NCEI's total dollar damage estimate (divided among the affected counties by local storm data experts). Total property damage from flood waters for Cameron County was $9.968 million.
Wider weather episode
Hurricane Hanna, the 2020 Atlantic season's first Hurricane, made landfall along the unpopulated Padre Island National Seashore on the mid-Kenedy County coastline as a Category 1 storm at around 5 PM Central Time Saturday, July 25th, carrying sustained 90 mph winds with gusts over 100 mph in a small portion of the inner eye wall. The hurricane spun slowly but steadily into southern Kenedy and northern Hidalgo County through just after midnight on the 26th, then through Starr County as a Tropical Storm before moving into Tamaulipas before daybreak and eventually near Monterrey, Nuevo Leon, by noon before dissipating during the evening of the 26th. Following the passage of the inner eye wall, broad feeder bands of torrential rains and gusty tropical storm force winds continued through the mid to late morning hours of July 26th, slowly migrating from east to west across the populated Rio Grande Valley.
Other than storm surge flooding, which peaked just north of Baffin Bay on the Kleberg and Nueces County coast near Corpus Christi, Hanna's memory for the Rio Grande Valley will be flooding rainfall, power outages, and an array of damage to poorly constructed buildings, from minor roof damage to complete demolition. Between 8 and 15 inches of rain fell from Port Mansfield to Harlingen, and along Interstate Highway 2 out through Mission and Sullivan City. The combination of high rainfall, locally high rainfall rates, and poor drainage left between 18 inches and four feet of water depth in many areas, most commonly from western Cameron through southeastern Hidalgo County, as well as a separate pocket in the Mission/La Joya/Sullivan City area. The rainfall wiped out 95% of the region's cotton crop; the combination of crop loss and production loss was more than one third of a billion dollars alone ($366 million)...most of which was in the Rio Grande Valley region.
At the peak of the storm, 250 thousand electric customers were without power, including all of Willacy County. Though storm surge was cut short by strong westerly flow across Cameron County, radiating swells did produce a notable surge of 3 feet or greater (estimated) from near Port Mansfield through Kenedy County. When the damage and economic loss is counted to infrastructure and agriculture combined, it is likely that Hanna cost at least one billion dollars across the Rio Grande Valley and the Deep S. Texas ranch country.
View location on OpenStreetMap → (26.3314, -97.8384)
Source: NOAA Storm Events Database, event_id 914453. Narrative written by the NWS forecast office that issued the report.