Tornado Information

Waterspout

A waterspout is a column of rotating wind that develops downward from a line of cumulus clouds to a body of water. A Cumulus cloud must be present for a waterspout to occur. The contrast of cold air overlying warm water provides a critical element leading to a waterspout event. Spouts can pack winds up to 200 miles per hour and will move across the water up to 10 to 15 miles per hour. They have been observed to reach heights of up to 10,000 feet.

Dust Devil

Dust devils are swirls that go upward to fizzle out in clear air; they aren't attached to clouds. While they are most commonly found on deserts and form when air at the ground becomes much hotter than the air above. The lighter, hot air begins rising and takes on a whirling motion that carries dust and sand upward. Top wind speeds seem to be around 60 mph.

Gustnadoes

"Gustnadoes" are weak vortices that are not connected to the cloud base, and by definition are not tornadoes. They are relatively shallow vortices associated with intense, small-scale shear in a thunderstorm gust front. They are not directly linked with rotation in the thunderstorm itself. Because they can produce whirling dust clouds (sometimes with small debris), they are very often misidentified as tornadoes. It takes a very alert and experienced spotter to tell the difference sometimes.

"Supercell" tornadoes

"Supercell" tornadoes are the largest and most most dangerous. They spin up under rotating storm and have winds up to 300 mph. They could be as much as a mile wide and last for hours.

Landspouts

Narrow vortex forms over  land under growing cumulus cloud; winds might reach 140 mph; last several minutes.

Sources:

http://desmoinesregister.com/extras/weather/torntypes.html

http://www.chaseday.com/tornadoes.htm

http://www.onlineweather.com/v4/data/Tornadoes.html