How a confluence of extreme weather, geography and timing created the flood disaster of Texas

As a succession of thunderstorms fed by the remains of Tropical Storm Barry Pummeled Texas’ Hill Country, tools started using the National Oceanic and Atmospheric Administration to detect extreme rainfall “Maximize color diagrams.”

The forecast models-a flash-flashing guide system called Flash and a program called the Multi-Radar/Multi-Sensor system that detects heavy precipitation uses a stair-like color series to communicate the seriousness of the rainfall and the flood risk, said David Gagne, a national center for atmospheric research, who is a national center for atmospheric. to improve weather models.

The floods that the Heuvelland of Texas have killed and killed more than 100 people were the result of a confluence of factors related to storm dynamics and local topography. Eventually they culminated in what Gagne called a ‘sausage-case scenario’.

“All ingredients came together in the wrong place, at the wrong time, at night during a holiday weekend,” said Gagne. “This was at the top of the dish.”

Although existing weather models can predict in advance flash floods, even the best models are struggling to represent the internal storm structure and predict where, within a few miles, the most difficult rainfall will strike.

In this case, the off-the-charts colors indicated on Friday morning that the South fork of the River De Guadalupe took a direct and long-term hit.

Then, instead of continuing, the storms got stuck.

The state climatologist John Nielsen-Gammon, the state of Texas, said that the thunderstorms were floating above the Texas Hill Country River, and dumped 10-12 centimeters of rainfall in about six hours. The series of storms “perfect in line with the river basin in South Guadalupe,” he said. The area is sensitive to flooding and was filled with campers at the edge of the river. If the storm had even been five miles in a different direction, it would not have produced that much destruction, he said.

It is difficult to know exactly how much rain has fallen. The basin that is flooded has no rain meter, even though it is in an area covered under the Texmesonet monitoring system that was created after a flash flood disaster that met Wimberley, Texas, in 2015. Maar de stortbui van vrijdag was een recordset voor die locatie en een storm die eens om de 1000 jaar werd gezien, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen, Nielsen.

Although predictors of the National Weer service had broadly warned about flash flashes, meteorologists and prediction experts said that the best weather models could not predict exactly where the most intense rainfall would fall, or that the flood would come out about a flood -sensitive basin.

“Even the most detailed weather forecast models are currently hardly able to resolve individual convective storms,” ​​said Nielsen-Gammon, adding that it would be “almost impossible” to predict well in advance whether the area would lead to the area.

Gagne rated the modeling tools that are available for NWS predaters. The most urgent warnings went out, he said, when the two NOAA -Tools showed the rainfall rates that started to spijken.

That gave people only a few hours to flee, assuming they received the warnings via mobile phone warnings, weather radio broadcasts or in other ways. Some residents probably didn’t get the alert and Kerr County has no siren.

Texas leads the nation in flood killing. The State had 1,069 floods of 1959-2019, according to research published by Hatim Sharif, a professor in civil and environmental technology at the University of Texas in San Antonio. That is 376 more dead than the next nearest is in that period – Louisiana.

During the six-decades study period, the San Antonio/Austin Area prediction office of the National Weather Service had the second highest number of flood-related deaths in the country. Many of them took place in the Hill Country, which some people call ‘Flash Flood Alley’.

The region is created by the Balcones Escarpment, a error zone of weather-burnt rock from Waco to Del Rio that distributes the state and can drop out serious storms.

“The Hill Country is in fact the first site obstacle that moves moist air from the wave experiences while moving further to the north. That offers extra lifting and leaving thunderstorms in the southern hill country,” said Nielsen-Gammon.

Sharif said that steep hills, narrow canyons are cut from limestone, quickly water from smaller creeks in larger watches in larger and then in swollen rivers. In many areas there is only a few centimeters of shallow soil on the foundation. Narrow creeks are etched in rock.

“It doesn’t absorb much water,” Sharif said. “It doesn’t take much time to flood those creeks … You have moved this venting area that water efficiently moves to the main stream.”

In just over 12 hours on Friday morning, the Guadalupe River rose about 20 feet, according to a river meter in Hunt, making a soft current in rapidly flowing rapids.

This article was originally published on nbcnews.com