The severity of the flash flooding that killed more than 130 people in Texas’s Hill Country was difficult to predict because the science is not yet available, a local meteorologist testified during Wednesday’s special legislative session.
The “prolific” flooding was made possible by the moisture leftover from Tropical Storm Barry, which made landfall on the east coast of Mexico on June 29, Pat Cavlin, a meteorologist at Houston CBS affiliate KHOU, said during Wednesday’s session.
The moisture then moved up to Texas and interacted with a slow-moving batch of storms over the middle of the state, combining over “one of the worst parts of the state when it comes to flash flooding events,” Calvin said.
MORE: What has been proposed at the Texas special legislative session on flooding crisis
Texas Hill Country is often colloquially referred to as “Flash Flood Alley” because the weather and landscape in the south-central Texas region work together to produce rapid flood events, according to the Texas Water Resources Institute (TWRI).
What made the situation unique was the presence of a mesoscale convective vortex (MCV) — “basically a mini area of low pressure” — that was slow-moving and stationary over Central Texas at the time of the torrential rains that caused the flash flooding, according to Calvin.
While meteorologists knew that the MCV would be in the area about 12 to 18 hours before the event unfolded, the amount of heavy rain that would be produced was not clear until just hours before Guadalupe River flooded, Calvin said.
Meteorologists began issuing alerts on July 3 that indicated there was cause for concern about the potential flooding that would take place within the next 24 hours.
Throughout the day, multiple National Weather Service (NWS) offices responsible for forecasting conditions in that region were highlighting in various forecast alerts and warnings that there was an elevated risk for flash flooding in south-central Texas due to the current weather pattern in place.
On the morning of July 3, the NWS Weather Prediction Center (WPC) upgraded the portion of south-central Texas, including Kerr County and surrounding areas.
At 1:18 p.m. on July 3, a Flood Watch was issued by the NWS Austin/San Antonio office, including Kerr County and surrounding areas through Friday morning.
MORE: These are the factors that contributed to the extreme Texas flooding
That alert mentioned that local heavy rainfall could cause flash flooding in the region, with isolated amounts of 5 inches to 7 inches possible, adding that “excessive runoff may result in flooding of rivers, creeks streams and other low-lying and flood-prone locations.”
At 6:10 p.m., the WPC highlighted the south-central Texas region, including Hill Country, as an area of increasing concern for slow-moving, training thunderstorms, or rounds of thunderstorms that remain in the same area, with the potential for rainfall rate exceeding 3 inches per hour into the evening hours and beyond.
The first flash flooding warning was issued at 1 a.m. on July 4 as thunderstorms began to roll in. At 4:03 a.m., a “rare” flash flood emergency warning was issued — indicating an imminent, ongoing threat to life and public property.
Around 4:20 a.m., the Guadalupe River hit a major flood stage, Calvin said.
While flash flood warnings are common in the region, flash flood emergencies are not, he added.
“This is an extreme event,” Calvin said. “It’s a freak event, really.”
Calvin noted that scientific and technological limitations make predicting a storm of this magnitude challenging.
“The science just isn’t there yet,” he said. “We are not at a point yet where we can identify where these individual pockets that lead to this life-threatening flash flooding can happen until pretty much it’s starting to happen.”
MORE: Texas flooding: Gov. Greg Abbott calls special legislative session for flood emergency planning
The deadly flooding over the Fourth of July weekend killed at least 136 people, including dozens of girls at Camp Mystic, situated on the Guadalupe River, Texas officials announced on Wednesday. Four people remain missing — include one adult male and one girl from Camp Mystic in Kerr County, Texas Gov. Greg Abbott said. Marble Falls Volunteer Fire Department Chief Michael Phillips is among the missing, and another person from Travis County, Abbott said.
Lawmakers filled House Bill 165 on Tuesday, which aims to create a model guide for local officials to follow regarding disaster response and recovery. The bill addresses contracting for debris removal; obtaining federal disaster funding; determining availability and construction of short-term and long-term housing and obtaining assistance from volunteer organizations.
Abbott called the special session in the wake of the flooding.
“We must ensure better preparation in the future,” Abbott said in a statement.
The special session is scheduled to last for 30 days.
Other items on the agenda for the special legislative session include a congressional redistricting plan, which could create more seats for Republicans, and a second attempt at regulating THC, the psychoactive compound found marijuana.
