Storm Surge/Tide — Willacy Island, Texas

2024-06-19 to 2024-06-21 · Willacy Island, Texas

Event narrative

The Texas Coastal Ocean Observation Network (TCOON)/C-MAN platform at Brazos Santiago (South Padre Island), along the Isla Blanca jetty just inshore from the beachfront, recorded a prolonged period of much higher than predicted tides, with departures generally 2 feet or more above predicted through the period. Astronomical tides were generally low, and this likely reduced the potential for property damage beyond severe and extensive beach erosion. The time period selected combined the above predicted tides with long-period swells and high waves, each which increased both run-up and wave set-up to cause erosion, which peaked at high tide but also occurred between high and low tide cycles.

An unknown amount of dune calving likely occurred along the beach front of along the narrower beaches northward to Port Mansfield was unknown.

Peak surge values - the difference between observed and predicted tides - were as follows for locations along the beachside (just inshore) and bayside of South Padre Island (south end). These are likely good proxies for values along the barrier island of Willacy County:

Brazos Santiago: 3.19 feet at 818 PM CDT on June 19th and 3.14 feet at 336 PM CDT on June 20th.

Coast Guard Station South Padre: 3.17 feet at 912 PM on June 19th and 3.08 feet at 342 PM on June 20th.

Peak total water levels above normally dry ground, which during periods of lower astronomical (seasonal) tides can have a negative value (meaning the water is farther out and the beaches wider) were as follows:

Brazos Santiago: 2.5 feet at 5 AM June 20th.

Coast Guard Station South Padre Island: 2.73 feet at 554 AM June 20th.

Note that tides at Port Mansfield (bayside), measured in Mean Sea Level, rose rapidly through June 19th and peaked on June 20th-22nd. Times used here reflect the period of most impact along the barrier island; while higher water levels continued into June 22nd, wave energy subsided steadily into the 21st and impactful flood conditions likely receded with it. Peak values ranged from 2.4 to 2.6 feet during the listed time period.

Wider weather episode

The difference between unusually strong (for late June) high pressure over the southeast U.S. and broad low pressure in the southwest Gulf brought a gradual increase in wave energy and rising tides (coastal run up) on the Lower Texas coast barrier island. Departures from predicted began to spike during the afternoon of June 18th, with the combination of wave energy (from 12+ foot waves and a 10-12 second swell period) beginning the onset of beach erosion (dune calving) along the barrier island. The erosion had at least two peaks - the morning of June 19th and June 20th when high tide combined with the strong run-up. The surface low consolidated into Tropical Storm Alberto at 10 AM CDT on June 19th, so the coastal flood events will be listed as storm surge.

In addition to dune calving on South Padre Island, a top-four highest total storm tide occurred at the Port Isabel tide gage. However, aside from increased water levels, there was no reported damage as of this writing. Should information on damage - for example, to docks and unprotected property - arrive, an event will be added for Coastal Cameron County.

Source: NOAA Storm Events Database, event_id 1197797. Narrative written by the NWS forecast office that issued the report.