How does a tornadoe form?
This site has a great explanation and diagrams.
http://www.weatherwizkids.com/tornado.htm
A tornado forms when there is a powerful thunderstorm that has a specific set of conditions. Here are the steps to understand how a tornado forms:
1. Warm, moist air is brought up into a storm cloud, also known as a thunderstorm, due to the wind patterns in the area.
2. The warm air rises rapidly within the storm cloud, while cooler air descends. This creates an area of rotating air called a mesocyclone.
3. The mesocyclone keeps growing and starts to draw in more warm air from the surface, creating an updraft. This updraft tilts the rotating air from vertical to horizontal.
4. As the rotating air nears the surface, it starts to spin faster and form a visible funnel cloud that extends downward from the storm cloud.
5. If the conditions are right, the funnel cloud can make contact with the ground, becoming a tornado.
For a more detailed explanation with diagrams and illustrations, you can visit the website http://www.weatherwizkids.com/tornado.htm. It provides a great breakdown of the formation of tornadoes.