Dozens confirmed dead: Why Texas flash floods were so unprecedented | DW News

Key Concepts

Flash flooding, Kerr County, Guadalupe River, Camp Mystic, search and rescue, disaster declaration, tropical storm, moisture-rich air mass, mesoscale event, mesoscale convective vortex, Texas Hill Country, Edwards Plateau, rainfall rates, flood watch.

Flash Flooding in Texas

• The Event: At least 43 people, including 15 children, died in flash flooding in South Central Texas, particularly Kerr County on the Guadalupe River. The flooding was triggered by months' worth of rain falling in just a few hours.
• Camp Mystic: A private summer camp, Camp Mystic, located along the Guadalupe River near Hunt, Texas, was severely impacted. Over 750 kids attend the camp, and initially, over 20 were unaccounted for, though this didn't necessarily mean they were lost.
• Response: Rescue teams are conducting search and rescue operations. Texas Governor Greg Abbott declared a disaster across 15 counties, deploying all available resources.

Meteorological Explanation

• Tropical Storm Connection: A tropical storm that made landfall in Mexico about a week prior saturated the air mass. This moisture-rich air mass then moved north into Texas.
• Unpredicted Intensity: While a flash flood watch was in effect, the extreme intensity of the flooding was not fully predicted.
• Mesoscale Event: The event was classified as a mesoscale event, meaning it was localized and difficult to predict more than 6 hours in advance.
• Mesoscale Convective Vortex: A key factor was a mesoscale convective vortex, a leftover swirl in the atmosphere from previous storms. This vortex parked over Texas Hill Country, drawing in more moisture and focusing downpours. Weather models couldn't detect this feature far enough in advance.
• Rainfall Rates: Bernett, Texas, received 9.1 cm of rain in 1 hour and 22 cm in 3 hours. The Guadalupe River rose 8 m in 45 minutes.

Current Situation and Forecast

• Worst May Be Over: The worst of the flooding is likely pushing east of Interstate 35.
• Terrain: The hardest-hit area is west of I-35, in the hilly terrain of Texas Hill Country and the Edwards Plateau. This terrain focuses moisture into small rivers, exacerbating flooding.
• Moving East: The bulk of the moisture is moving east, and there isn't much "oomph" for more thunderstorms. The extreme flood scenarios are likely winding down.

Synthesis/Conclusion

The flash flooding in Texas was a tragic event resulting in significant loss of life, particularly impacting children at Camp Mystic. While a flash flood watch was in effect, the extreme intensity was due to a localized mesoscale event involving a mesoscale convective vortex drawing in moisture from a previous tropical storm. The worst of the flooding is likely passing, with the moisture moving east, but the coming days will be critical for search and rescue and recovery efforts.