Tornadoes are one of the most powerful and deadly weather phenomena on land. They can destroy entire town and fling debris over great distances. However, how does a tornado form? The answer lies in the atmosphere and air pressure.
Weather is created by changes in the temperature and pressure of the atmosphere. Tornadoes are formed when both high pressure and low pressure air interact. A tornado happens in the same way a whirlpool in your sink or bath tub happens. A low internal pressure draws in high pressure air to form the vortex and eventually the tornado.
Tornadoes are normally formed when a thunderstorm occurs. The most common type of thunderstorm for forming tornadoes is the supercell. This is because this type of storm already has rotation occuring within it called a mesocycle. The tornado starts forming when a downdraft brings the mesocycle down near the grown starting the creation of a vortex.
The next step of the cycle starts when cloud wall is formed. This happens when the vortex starts drawing down the cloud into a funnel. The most dangerous part of the tornado is not the visible part its the winds created by the high pressure air being sucked into the tornado. This is what creates the destruction path scene after a tornado passes.
The next step is the maturation and strengthening of the tornado. Like any major storm phenomena, a tornado needs energy to increase in strength and sustain itself. The source of this energy is the moist warm air that is drawn into the tornado. The maturation part of the tornado’s life cycle is the most destructive since it not only increases in intensity, but also can last a long period of time.
Fortunately the down draft of air has cooled so it start to shut down the funnel it created by cutting off its supply of warm air. This begins the end phase of the tornado. The tornado begins to thin and become less well developed. Eventually it completely loses energy and the funnel completely disperses.
Tornadoes don’t just form singly. They can also form in groups called families or outbreaks. These are often weaker tornadoes created by the intense rotation of a strong and larger tornado. While weaker the biggest tornado ever can create a lot of damage.
There is a lot of great articles on Universe Today that you can enjoy. There is a great article about how the biggest tornado can be determined. There is also an interesting piece about a lightning storm generated by a volcano in Chile.
There are also some great resources online. There is a great article on USA Today.com about Tornado formation. You can also check out a similar article on howstuffworks.com.
You can also listen to Astronomy Cast. There is an excellent episode that talks about the atmosphere.