Here in Kansas City, my adopted hometown, we are having Severe Weather Awareness Week. And this means that if there is any severe, scary weather, we are supposed to be aware of it. Also we are supposed to learn what to do if there is severe weather. Of course, my brothers already know what to do in these cases. They just hang out under Mom's feet and they pant and drool a lot. And also Mel crawls under Mom's bed or under her computer desk.
Anyway, today is "Tornadoes Day," so I thought I would learn a little bit about tornadoes so that I could tell you how to be more aware, in case one ever comes to your house.
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| Greensburg, KS tornado, 2007 |
If you have seen that movie
The Wizard of Oz, you will know that tornadoes can pick your whole house up with you and your little dog in it, too, and take you to a strange place where there are lots of short people singing in high-pitched voices. But if you have watched the news reports, you will know that it's much more usual for tornadoes to just knock your house down with you inside it and smash you.
Every year about 70 people get killed by tornadoes in the U.S., and about 1,500 people get injured. Tornadoes can happen during any season, but they happen more often in the spring and early summer. There's a part of the U.S. that is called "Tornado Alley," and this is where the most tornadoes happen. The U.S. has more tornadoes than any other country, but tornadoes can still show up in lots of different places. Well, except for Antarctica. There has never been a tornado there, probably because there is no warm air, which is one of the main ingredients you need to make a tornado.
So anyway, if you were going to make your own tornado, you would first need some warm, humid air near the ground, and also a strong south wind. Then way up high, you need cold air with west or southwest winds. The warm air is not as dense as the cold air, so once it gets started, it will move up into the cold air, and this makes a thunderstorm.
After that, if the wind direction changes, you get something called
wind shear, and the hot air in the middle between the top layer of air and the bottom layer will start rotating. And then you have a tornado!
Some tornadoes are pretty narrow at the bottom, like maybe 250 feet across, and they only go a few miles before they get tired of being a tornado and they go away. But some really big tornadoes are two miles wide, and they can travel several dozen miles across the land before they fall apart.
The average speed of a tornado is 30 mph, but some are slower, and others go as fast as 70 mph. The strongest tornadoes have winds that rotate at 250-300 mph. Sometimes a tornado will pick up something light and carry it for several miles. A tornado can also lift something heavy, like a railroad car, but it can't carry it very far. I think a tornado could probably pick up a little dog like me and take me quite a long ways before it dropped me. And if that happened, I would get really dizzy, and it would hurt a lot to be dropped, so that's one reason why I don't want to have any tornadoes come around here.
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EF4 tornado damage. An EF5 tornado
would probably have taken the pool table, too. |
People like to talk about how strong a tornado is, and so they use something called the Fujita scale. On this scale, an F0 tornado is very puny and might only knock a few branches off of trees, and an F5 tornado is the really bad kind that can tear your house off its foundation and flip your car over a couple of times. When the Fujita scale was first created, you just had to rate tornadoes kind of by guessing at how strong they were after you looked at the damage they left behind. But now there is something called the Enhanced Fujita Scale, with ratings from EF0 to EF5, and it is more exact. There is also a TORRO Scale that rates tornadoes from T0 to T11.
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| Moore, OK, 1999 tornado |
The tornado that killed the most people ever was the "Tri-State" tornado on March 18, 1925. This tornado went through parts of Missouri, Illinois, and Indiana, and it killed 695 people. The most people that got killed by a tornado in one town was 234 in Murphysboro, Illinois. And the city that has been hit by the most tornadoes is Oklahoma City. If you like to read about this kind of stuff, you can find a list of the 25 worst tornadoes ever
here.
Every year, about 1,000 tornadoes hit the U.S., but this number is a pretty rough estimate because the way of reporting and recording tornadoes over the years has changed. The chance that a tornado will hit the square mile of land where you live is about once in a thousand years. Of course, in some parts of the country, your chances of being in a tornado might be bigger, and in other places it's smaller. Also if you are a storm chaser or your name is Dorothy Gale, you are lots more likely to have a close encounter with a twister.
Anyway, we were supposed to have tornado drills here today, so that everybody would know how to hide from a tornado if one comes around. But we are going to have rain and thunderstorms, so the tornado drills got put off until Thursday so that people won't be confused about whether it's a drill or the real thing!
