Physical Science 101
Severe Storms - Tornadoes

Outline for the video Tornado!.

This video will be shown during classtime. The outline provided below is simply a list of the major topics covered in the video and is not intended to be a substitute for viewing the video. The entire video may also be viewed on YouTube at the following link: NOVA: Tornado!.

I. Tornado Alley
II. Tornado Characteristics and Formation
III. Tornado Chasing
IV. Tornado Experiments
V. Barneveld, Wisconsin


Rapidly rotating winds around a small area of intense low pressure.
Commonly known as twisters or cyclones.

Basic Stats

Diameter: 100 to 600 m average - range few meters to 1600 m
Movement: SW to NE (North America)
Ground Speed: 35-75 kph average
Duration: few minutes to hours
Path Length: 7 km average
Rotation: counterclockwise and clockwise (rare) in the N. Hemisphere

Fujita Scale

Tornado Categories based on wind speeds
Scale : Speed : Damage
F0 : <72 mph : light
F1 : 73-112 mph : moderate
F2 : 113-157 mph : considerable
F3 : 158-206 mph : severe
F4 : 207-260 mph : devastating
F5 : >260 mph : incredible
Recently replaced in U.S. by the Enhance FS

Stages of Development

1) Dust-Whirl Stage:
2) Organizing Stage:
3) Mature Stage:
4) Shrinking Stage:
5) Decay Stage:

Tornado Formation

Formation along the Polar Front
Formation along the Dry Line
Tornado Alley