Tornadoes and Thunderstorms

With a tornado there is no drain. Instead, there is a thunderstorm cloud. A typical thunderstorm cloud can accumulate a huge amount of energy. If the conditions are right, this energy creates a huge updraft into the cloud. But where does the energy come from?

Photo courtesy NOAA

Clouds are formed when water vapor condenses in the air. This change in physical state releases heat, and heat is a form of energy. A good deal of a thunderstorm's energy is a result of the condensation that forms the cloud. According to Encyclopedia Britannica:

For every gram of water condensed, about 600 calories of heat are made available. When the water freezes in the upper parts of the cloud, another 80 calories of heat per gram of water are released. This energy goes to increase the temperature of the updraft and, in part, is converted to kinetic energy of upward and downward air movement. If the quantity of water that is condensed in and subsequently precipitated from a cloud is known, then the total energy of a thunderstorm can be calculated. In an average thunderstorm, the energy released amounts to about 10,000,000 kilowatt-hours, which is equivalent to a 20-kiloton nuclear warhead. A large, severe thunderstorm might be 10 to 100 times more energetic.

In supercell thunderstorms, the updrafts are particularly strong (see the links at the end of this article for information on supercells). If they are strong enough, a vortex of air can form just like a vortex of water forms in a sink. An air vortex under a thunderstorm cloud is a tornado.

Photo courtesy NOAA Supercell

The tornado reaches down out of a thundercloud as a huge, swirling rope of air. Wind speeds in the range of 200 to 300 mph are not uncommon. If the vortex touches ground, the speed of the whirling wind (as well as the updraft and the pressure differences) can cause tremendous damage.

Photo courtesy NOAA A tornado snakes down out of the thundercloud and eventually touches ground. When it does, it picks up a swirling cloud of dust and debris.

The tornado follows a path that is controlled by the path of its parent thundercloud, and it will often appear to hop. The hops occur when the vortex is disturbed. You have probably seen that it is easy to disturb a vortex in the tub, but then it will reform. The same thing can happen to a tornado's vortex, causing it to form and collapse along its path.