[SystemSafety] Texas Floods

[Prof. Dr. Peter Bernard Ladkin]

I can tell from the discussion that extreme weather events are close to a lot of people's hearts :-)

Most of the technical questions I had are answered by this superb blog post by Alan Gerard

https://balancedweather.substack.com/p/balancedwx-special-tragic-flash-flooding

Thank you to the weekday Nature briefing email for pointing me there.

Gerard looks inter alia at radar data from Laughin AFB, which is west of San Antonio pretty much on 
the Rio Grande and thus the Mexican border, just outside Del Rio, from which the weather balloon 
that detected unusual amounts of atmospheric moisture was launched on Thursday, and whose 
measurements triggered the considerations at the NWS Weather Prediction Center in Maryland.

Gerard points out that there was very intense rainfall pretty much localised on the watershed of the 
South Fork of the Guadelupe River, which is where Camp Mystic was. The NWS knew in real time that 
something was happening. They had issued a general warning message, read by professionals, on 3 July 
at 18:10 CDT, mayn hours before the start of the event, about the potential for extreme weather and 
flooding, The first NWS flash-flood warning message at 01:14 CT for Kerr County, as the event got 
under way, included a tag that should have automatically triggered the Wireless Emergency Alert 
system, which I understand is a cell-broadcast system similar to what we now have in Germany after 
the 2021 floods. And then more alerts also with WEA tags were issued as things got worse. So it 
seems the NWS did what it could and what was expected.

That answers my question about why didn't the professionals know. They did know, and they did 
everything that could be expected. I guess an inquiry will tell us why that didn't help as one might 
have expected it should have. One issue is likely that cell phone coverage may not be very good in 
that area.  Apparently what went on in Hunt, the community at the confluence of the Forks, was 
pretty extreme. Water level rose over three stories (from 7.7 ft to 29.45 fr) and the gauge broke.

Gerard points out that we don't have the tools (yet) to predict such very localised downpours. Just 
as we didn't know in 2021 where all that atmospheric moisture over Germany and Belgium was going to 
come down. And the effects are very dependent on topography. And, as I found out in Bielefeld in 
2023, not even when the details are obviously wrong is it easy to get them corrected.

PBL

Prof. Dr. Peter Bernard Ladkin
Causalis Limited/Causalis IngenieurGmbH, Bielefeld, Germany
Tel: +49 (0)521 3 29 31 00