Scientists study weather patterns to try to lean what conditions must be present for a tornado to from. They have two goals. First, they would like to be able to give people enough before a tornado strikes. Second, they hope someday actually to prevent a tornado from forming. This problem is complicated since there are three different kinds of tornadoes.
A mini tornado cuts a path less than a kilometer long. It is very short-lived, and wind are rarely more than 160 kilometers an hour. Thus, damage is limited. A mini tornado may tear roof from a house, but it cannot destroy the entire building.
More destructive than the mini tornado is the average tornado. It is the most common-and can last up to twenty minutes, covering about one-and-a-half kilometers. The funnel is generally dark gray since dirt and debris are drawn upward. Average tornadoes are the easiest of the three kinds to predict.