Tornadoes are one of the most dangerous naturally occurring phenomena in the world. They're unpredictable, and that unpredictability can make them scary. We are starting to actually understand them, though, and understanding them can help us make sure we're safe around them. Here's a bit about what we know about tornadoes, and how to stay safe during one.
How and Where They Are Likely to Form
Despite how famous they are for their destruction, tornadoes are pretty rare. They occur mostly in the Midwest United States, and even then only in 1 in 1000 thunderstorms actually produce a tornado. Tornadoes form from very tall thunderstorm clouds called cumulonimbus clouds, but not all cumulonimbus thunderstorm clouds are going to form tornadoes. There are other factors that must be present.
In addition to large cumulonimbus clouds being present, the wind direction and speed has to be different at high altitudes than it is at low altitudes. So, if the wind twenty feet in the air is going north, the wind at, say, fifty feet up needs to be going south, and at a different speed. Due to this change in wind direction and speed, a funnel starts to form and it sucks the warmer air at the ground up into it. The funnel gets longer and longer, stretching from the cloud until it hits the ground. When the funnel hits the ground, only then is it considered a tornado.
Different Kinds of Tornadoes
Even though there are many different strengths of tornadoes, there are only a couple different types of tornadoes. These are supercell and non-supercell tornadoes.
Supercell tornadoes are the most common and usually the most dangerous type. These are tornadoes that form from supercell storms, where the updrafts and downdrafts that we mentioned earlier are pretty much equal, only varying slightly in speed. The reason that supercell tornadoes are usually the most dangerous is that they tend to stay on the ground the longest. When it comes to the amount of damage a storm can cause, it's not always about how strong the winds are. With tornadoes, the winds are always going to be strong. The real danger comes with duration of the storm. The tornado that stays on the ground the longest is usually the most devastating.
Non-supercell tornadoes are also dangerous, but do not usually last as long as supercell tornadoes, and they're also less common. Whereas supercell tornadoes are formed with wind moving horizontally, a non-supercell tornado is formed by air moving vertically. As wind moves from the funnel cloud to the ground, it stretches the rotating cloud until it touches the ground and becomes a tornado.
Scale Measurements of Tornadoes
Measuring tornadoes is something that has a long history, and even has some recent changes that makes it really interesting. Until February of 2007, the Fujita scale with the standard measurement of tornado strength, and to a degree it still is. The Fujita, or F scale was a number you could give a tornado and other scientists would know how strong the winds were. The scale went from F1 to F5, with F1 being the weakest tornado and F5 being the strongest.
In 2007, while the Fujita scale was working well for scientists, it was enhanced to account for the damage they cause. For instance, with the original Fujita scale, a scientist would know the estimated wind speed of an F3. With the Enhanced Fujita scale, a politician could know that an F3 is likely to level a school.
If you live in an area where tornadoes are likely to occur, it's so important that you know what to do when you hear that warning siren sound. If you're home, get to a basement as soon as possible and stay away from the windows. The walls in your basement won't collapse because they're below the wind, and the glass from windows can become extremely dangerous, so it's best to stay as far away from windows as possible. The one thing to keep in mind here is that if you live in a mobile home like a trailer, it's best, if you can, to have a storm shelter you know you can get to quickly, as trailers simply lack the structural strength and weight to stand up at all to even relatively minor tornadoes.
By: Steven Moore