Historic flooding continues in the southern Plains

It has been a wet few weeks in Texas and Oklahoma with the wettest month on record for several cities now in both states, and they can't seem to catch a break. Another deluge of rain Saturday sent thousands heading for higher ground as a torrent of water traveled down area rivers. The San Marcos area was arguably the hardest hit. It is a city right along I-35 between San Antonio and Austin. Rainfall from the area topped 9 inches in just a few hours' time as you can see by the 24 hour rainfall totals below…

 

Even for dry soils, 9 inches is a copious amount of water, but the area had already seen nearly a foot of rain this month leaving little room for the soil to soak up the extra water. So it just runs off into local rivers… one in particular. The Blanco River caught the brunt of the water and rose quickly… in fact, it rose faster than anything I have seen before that wasn't a desert canyon in the Southwest U.S. The river level jumped 28 feet in just 90 minutes!

 

 

These are two river gauges; one near the start of the river and the other as it crosses I-35 in San Marcos. The sharp jump in the graph says it all… a wall of water tearing down the river. It rose so much and so quickly that many living next to the normally calm stream were caught off guard. Those that couldn't get out fast enough took refuge on their roofs, in tall trees, and other high objects just to escape the torrent. This picture is from I-35 in San Marcos from KXAN…

 

So why so much rainfall??? Well, it actually has to do with El Nino. There has been a direct link between the tropics and the southern Plains for nearly a month sending copious amounts of moisture up into the southern U.S. via the sub-tropical jet stream. Storm systems will pass through this nearly endless supply of moisture and explode with heavy rain and thunderstorms. Check it out in the picture below…

 

I'm not going to go into a huge explanation of what this means, but Eric Blake from the National Hurricane Center tweeted this picture to show the state of the atmosphere. Look at what I've circled. The colors can indicate how the atmosphere is behaving in different parts of the world and how certain locations are connected to each other. The part I have circled shows those darker colors stretching from the Tropics into the southern U.S. indicating a link between the two. This is what has ultimately fueled the heavy rain across much of the center of the country over the last few weeks. Check out rainfall estimates nationwide on the map below… nearly 2 foot totals so far this month in Texas and Oklahoma…