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Tornado Alley September 3, 2007

Posted by physics309 in McKinney, San Angelo, Science.
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My posting of the other day has put me in a stormy mood. I don’t mean it put me in a bad mood, I mean it just made me think about memorable storms. As a result, I’ve decided to spend the next few days discussing some of these storms, beginning with the smallest and moving into the worst of all.

I spoke of the nature of the storms of north Texas in a previous posting. This is the violent weather of Tornado Alley, which stretches from north Texas up into the Dakotas, with the most violent region being smack in the middle of Oklahoma. The central region of the nation is peculiar in the way there are strong air currents coming from the Gulf of Mexico and cool air masses moving down from the north. The southerly air masses are filled with moisture and heat and when they collide with the cool, northerly air masses the moisture will condense and the heat will cause violent thunderstorms. Frequently, tornadoes will also result. More tornadoes occur in Tornado Alley than the rest of the world combined.

If you like storms, and I do, this is the place to be. They are beautiful and awe-inspiring. They are also dangerous and you have to take care. I would think that anyone from the region could tell you not to drive into moving water, no matter how shallow it appears. It only takes a few inches of water to sweep a car away. But, it doesn’t matter how many times they warn the public about this, it seems someone gets killed in every storm because they drove into moving water and got swept away.

Another danger is low lying areas. These storms are so violent and can drop so much rain that low lying areas will flood so quickly you can’t outrun the rushing water. This can even happen far downstream of the storm itself. Anyone camping is warned not to make camp in an arroyo because a storm upstream will result in a mountain of water rushing down. Yet, someone gets killed this way every year.

Even in the towns, low lying areas can get dangerous. I was almost caught by one once. I was driving in a storm and took a turn. By the time I realized the low lying intersection was flooded, it was too late. I crashed into the flood waters and was actually floating. I was trying to think of what I was going to do when I realized I was still going forward as a result of my momentum. Eventually, I could feel my tires make contact with the ground on the other side and I just drove off with no damage done. I took an extra careful look before going around that turn in the future, though.

These storms can come any time of day, but seem to have a preference for the early morning hours. We would frequently wake up during the night to the sound of a big storm. I would lay in bed and listen to the sounds and feel the house shaking to the violence, before it quickly ended and I would go back to sleep. One night, the cat wouldn’t come in at bedtime and I just left it outside. I woke that night to one of these storms and was just about to drift off to sleep in the quiet afterwards when I heard this pathetic, ‘Meeooowww!’ I went to the front door and found this toothpick of a cat. It looked just like something from a Bugs Bunny cartoon with its hair soaked all the way through and looking like it was half its normal size. It was weeks before it would even step outside the house again.

San Angelo had some terrific thunderstorms, some of the most violent I’ve ever seen. Without knowing it, we actually got a taste of things to come on the Memorial Day weekend of 1995.

We went camping at Dinosaur Valley State Park, just outside Glen Rose and about an hour west of Ft. Worth. This is a very cool state park that preserves dinosaur footprints. You can go walking down through the river and see all of these footprints preserved in the stone, set there tens of millions of years ago on an ancient seashore. An interesting note is the big hole where a slab with some of the best footprints was taken out. I finally got to see this slab in the fall of 2005 when I visited the American Museum of Natural History in New York City.

We camped out in the park with our 18-month old baby and had a good time of it playing in the shallow river. That evening we witnessed an amazingly violent thunderstorm out in the distance. We watched the lightning show for a long time before finally going to bed, after feeling comfortable it wasn’t coming towards us (we had learned our lesson at Lake Texoma). We moved to San Angelo almost exactly a year later and people were still talking about that storm and how much damage it had done. Even after a year there were still houses with damaged roofs. So many were damaged during the storm that they hadn’t been able to fix them all even after a year. The roofing business is a good one to get into in Texas.

Just arriving in San Angelo was an adventure. We rented a large truck to move all of our household goods. I was driving the truck and towing one car while my wife drove the other car. I saw a mileage sign for San Angelo and, based on my speed, estimated we would be in San Angelo in an hour. A storm was brewing ahead of us, but I didn’t think much of it. But, it kept getting worse and worse, causing me to continually slow down. I saw another mileage sign after a while and, based on my new speed, estimated it would take an hour to get to San Angelo. We kept going on and the storm kept getting worse, causing us to slow down even more. I saw yet another mileage sign and again estimated it would take us an hour to get to town! This was becoming a Twilight Zone kind of trip! We heard on the radio that tornado warnings were being issued for the area ahead of us, so we were driving into the teeth of a bad storm. This made us pull over and wait for the worst to pass. The roads out there are really empty and we hadn’t seen anywhere to take cover, so we just pulled to the side of the road and hunkered down to wait for the storm to end. This really didn’t take very long. These storms have an enormous amount of energy, but usually don’t last very long. In short order, things had cleared up and we were able to get back on the road.

There wasn’t a lot of damage in San Angelo, but some of the surrounding little towns got hit. And, this was our introduction to the west Texas weather. Storms were few and far between, but they were real barn busters when they came in. I’ve heard meteorologists talk about the weather in west Texas and particularly in the panhandle region of Texas

There’s hardly an area in the country with worse weather than that region. The panhandle is known as the Llano Estacado, the Plain of Stakes. There are actually several stories of where this name came from, but my favorite is that the Spanish explorers found the area so flat and featureless that they were afraid they would get lost and drove stakes in the ground to leave a trail so they could find their way back out again. Looking at the names of the towns in the area tells you what its like: Levelland, Lamesa, Plainview. It’s also about 5000 feet in altitude with a long, slow drop off to about 1000 feet in the rest of northwest Texas. Air masses can move gently from the north and suddenly drop down that incline, or meet another air mass coming up from the south. With few trees to provide shade, the ground heats up and causes convective air currents, resulting in sudden thunderstorms. Dust devils are common sights out there and there are times you can witness many at once. These are mostly gentle areas of convection that will lift up the dust and debris from the ground and make it swirl around in the air (also very common on Mars). We use to chase them around the playground when I was kid. I was so used to this phenomenon that I would talk about them in my classes in South Dakota without realizing that many of the students had no idea what I was talking about. All of these features create havoc for the weather forecasters.

The local ones forecasters love to tell stories about the out-of-staters that show up in the region for the first time and try to make weather forecasts like they would somewhere else, just to be stymied by the unpredictable and violent nature of the weather and caught by surprise by how quickly it will change. You can always tell a longtime west Texas resident by the way they will always be glancing at the sky, checking the weather. They know, just because it was nice five minutes ago doesn’t mean it will be nice five minutes from now.

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