Storms kill at three people in Louisiana; flood risk looms for Texas

August 16, 2024

Swarms of strong to severe thunderstorms rolled along the Gulf Coast on Monday, bringing flooding, destructive winds, large hail and tornadoes. More severe storms are possible Tuesday and Thursday, especially, when parts of Texas and Louisiana may face a serious threat of dangerous flooding.

The destructive storms killed at least three people in Louisiana on Monday, according to the state’s Department of Health:

A person died near the town of Henderson, just east of Lafayette in St. Martin Parish, after a camper rolled over because of high winds.
A 31-year-old woman, who was nine months pregnant, was crushed when a tree fell on a trailer in Port Allen, which is about midway between Lafayette and New Orleans along Interstate 10. The fetus did not survive and was counted as an additional storm-related death.

The same storms spawned a damaging tornado in Sulphur, La., just west of Lake Charles. The twister was part of a squall line that brought widespread damaging winds, some to hurricane force. A gust of 75 mph was clocked in Calcasieu Parish, La., with a gust to 80 mph in nearby Lafayette. Storms progressed east into the Florida Panhandle, where winds gusted to 82 mph in Santa Rosa, near Destin.

Storms along the eastern Gulf Coast trained, or moved repeatedly over the same areas, dumping heavy rains and causing localized flooding. Mobile Regional Airport in Alabama tallied 7.12 inches within 48 hours, with 6.94 inches in nearby Daphne, just east of Mobile Bay, and 6.09 inches at Mobile’s downtown airport.

A batch of rotating thunderstorms or supercells produced severe hail across parts of southern Texas. Baseball-size hail occurred in Zapata and Hidalgo counties along the Rio Grande.

To the north, storms sparked prolific lightning that blasted a hole in runway 13-R at Houston’s Hobby Airport. The runway was closed while crews worked to perform swift repairs.

Storms continued into Tuesday morning and were zipping east across the northern half of the Florida Peninsula to start the day. A tornado watch was in effect until 1 p.m. as a broken line of storms, leftovers from Monday’s severe weather, rolled toward the Atlantic coast.

A brief lull in storminess was expected Wednesday, but more dangerous storms and flooding were slated for later this week, particularly on Thursday.

Thursday’s severe weather risk

Thursday’s severe weather risk zone is focused on parts of central Texas, where the Weather Service’s Storm Prediction Center has drawn a Level 2 out of 5 risk. It includes Dallas, Abilene, Waco, Austin and San Antonio. A broader Level 1 risk stretches south and east toward the coastline, encompassing Corpus Christi, Houston, Shreveport, La. and New Orleans.

Initial storms along the Interstate 35 corridor from Dallas to San Antonio may be supercells that produce large hail. Those storms will coalesce and shift southeast toward the coast, as will one or more lines or clusters with a damaging wind threat as well as torrential rainfall.

There is at least some risk, moreover, that storms will continue into Friday, and could become strong to severe. The Storm Prediction Center has highlighted an area to keep tabs on, namely from central Louisiana northeast toward Jackson, Miss.

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Dangerous flood potential

Concern then grows in eastern Texas and central and northern Louisiana for flooding. Outflow boundaries, or the leading edge of cool air exhaust from storms to the west, could ignite nonsevere thunderstorms along the Interstate 10 corridors between Houston and New Orleans, which would then spread as far north as Shreveport.

Those storms would then ingest large amounts of moisture from the Gulf of Mexico, leading to efficient downpours that could produce rainfall rates of 2 to 3 inches per hour. That rain will be made heavier by diffluence, or spreading of air, aloft. That creates a vacuum of sorts in the upper atmosphere, which enhances upward motion, sucking moisture upward from below and bolstering rainfall rates even more.

The Weather Service has introduced a Level 3 out of 4 risk of flash flooding and excessive rainfall in that region, and the agency is considering upgrading to a top-tier High risk in a later forecast.

“It seems probable that a High Risk consideration may need to be given in future forecasts, especially if the ‘bull’s eye’ of heaviest rain remains over this hard hit areas of Texas and Louisiana,” wrote the agency. Forecasters are especially concerned with training, downpours over areas that have already faced flooding.

Portions of eastern Texas and Louisiana are already waterlogged after relentless rounds of storms over the past three weeks, some of which caused deadly flooding in early May and pushed rivers to near-record levels. The previous rainfall, saturated soils and high river levels will make it much easier for renewed flooding. Eleven of the past 19 days have featured at least a Level 2 out for 4 flood risk in the greater Houston area.

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