Storm Surge/Tide — Coastal Kenedy County, Texas

2020-07-25 to 2020-07-26 · Coastal Kenedy County, Texas

Event narrative

Storm surge generated by Hurricane Hanna pushed tide levels above ground in excess of 3 feet along coastal Kenedy County beginning by mid afternoon of July 25th and likely continuing through landfall at approximately 4 PM local standard time on the mid-Kenedy County coast along the Padre Island National Seashore (PINS). Though high water marks had not been specifically provided on PINS at the time of this writing, ground and aerial surveys suggested water levels above ground may have exceeded 4 feet above normally dry ground on portions of PINS in Kenedy County. Levels up to 5.48 feet above normally dry ground at the shoreline (Mean Higher High Water) were noted along the Coastal Bend just north of Kenedy County at the north entrance to PINS. Though Hanna did not create any known new cuts into the Barrier Island of Kenedy County, visual evidence from ground and aerial post-storm surveys indicated eight rearranged washover channels from the combination of storm surge and breaking waves. Most dunes were eroded to varying levels on the Kenedy portion of PINS.

Along Laguna Madre, tides ran out on northwest flow ahead of landfall, but rose sharply on strong southeast to south flow post-landfall. At the Texas Coastal Ocean Observation Network platform at Rincon del San Jose, near the land cut about one-third the distance north of Port Mansfield, return flow pushed water levels to an estimated 3.43 feet above Mean Sea Level (MSL; note: an equivalent value based on the MHHW datum was not available) at 418 AM CST July 26th. The high water levels - based on 2.5 feet or greater MSL as proxy, began at 8 PM CST July 25th and continued through 11 PM CST July 26th before slowly receding.

Other than severe beach erosion, there was little known property damage due to Storm Surge in largely unpopulated coastal Kenedy County. However, damage estimates to fishing huts and other coastal properties as calculated from NCEI's total dollar damage estimate (divided among the affected counties by local storm data experts) was $11,866 for coastal Kenedy County.

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.

Source: NOAA Storm Events Database, event_id 914320. Narrative written by the NWS forecast office that issued the report.