Friday, May 14, 2010

Blow Baby Blow

Most nights Tony and I turn on the radio at bedtime and listen to St. Louis On The Air, a locally produced program on our NPR station St. Louis Public Radio.  The show actually airs in the morning, but they conveniently rebroadcast it at 10:00.  Last night's interesting show was about severe weather and storm warnings.  Although I didn't stay awake to hear the whole thing, the first part was about tornadoes, and they kept referring to categories.  I've heard of hurricane categories, but wasn't familiar with any others, so this morning I did a bit of research.

Turns out that tornadoes are measured on the Fujita Tornado Scale (or "F Scale"), which was developed in 1971 by Professor Theodore Fujita of the University of Chicago.  It classifies tornadoes according to wind speed and damage. The categories are based upon the estimated maximum winds occurring within the funnel, and the intensity of a tornado is determined afterwards by doing a survey of the damage

In case you're curious, here's the Fujita Scale:

(FO) Gale Tornado (40 - 72 mph)
Light damage: some damage to chimneys, breaks branches off trees, pushes over shallow-rooted trees, and damages sign boards.

(F1) Moderate Tornado (73 - 112 mph)
Moderate damage:  The lower limit (73 mph) is the beginning of hurricane wind speed, peels surfaces of roofs, mobile homes pushed off foundations or overturned, and moving autos pushed off roads.

(F2) Significant Tornado (112 - 157 mph)
Considerable damage:  Roofs torn off the frames of houses, mobile homes demolished, boxcars pushed over, large trees snapped or uprooted, and heavy cars lifted off ground and thrown.

(F3) Severe Tornado (158 - 206 mph)
Severe damage:  Roofs and some walls torn off well-constructed houses, trains overturned, most trees in forest uprooted, and heavy cars lifted off ground and thrown.

(F4) Devastating Tornado (207 - 260 mph)
Devastating damage:  Well-constructed houses leveled, structures blown off weak foundations, and cars and other large objects thrown about.

(F5) Incredible Tornado (261 - 318 mph)
Incredible damage:  Strong frame houses are lifted off foundations and carried a considerable distance and disintegrated, automobile sized missiles fly through the air in excess of 100 meters, and trees debarked.

(F6+) Inconceivable Tornado (319 - 379 mph)
The maximum wind speed of tornadoes is not expected to reach the F6 wind speeds.


  1. Those wind speeds are incredible! Good post :o)

  2. Okay, Now I want a basement, a hole to hide in!!!

  3. Wow! I had no idea about this scale. Thanks for sharing this.

  4. CambridgeLady-Thanks.

    Kathy's Klothesline-The vast majority of tornadoes can be classified as F0 or F1. Only 1% are F4 and 5; however, they are responsible for 2/3 of deaths.