Tornado

From Environmental Technology

A tornado is "a violently rotating column of air, pendant from a cumuliform cloud or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud." A vortex has to be in contant with the ground and cloud base to be classified as a tornado. The most damaging and/or deadly tornadoes come from supercells. Supercells are rotating thunderstorms with a well-defined radar circulation that is called a mesocyclone. Tornado formation is believed to be based mainly on things which happen in and around the mesocyclone. Tornado formation is believed to be based mainly on things which happen in and around the mesocyclone. Tornadoes can come from any direction; however, most move southwest to northeast or west to east. They can also changed direction. Rain, wind, lightning, and hail could occur with a tornado but not necessarily. in order to keep going, tornadoes need a source of instability and a large-scale property of rotation. They can last for just a few seconds to up to an hour, most lastly less than 10 minutes.

[edit] Reference

The Online Tornado FAQ (http://www.spc.noaa.gov/faq/tornado)