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Tornado observed by the VORTEX-99 team on May 3, 1999, in central Oklahoma. Note the tube-like condensation funnel, attached to the rotating cloud base, surrounded by a translucent dust cloud.
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Courtesy of NOAA

Tornado Scales

Before 1971, there was no way for scientists to rank tornadoes by their strength. How big the tornado looked had no bearing on how strong it actually was. In 1971, Professor Fujita came up with a system to rank tornadoes according to how much damage they cause. This was called the Fujita Scale.

As of February 1, 2007, a new scale for rating the strength of tornadoes is being used. It is called the Enhanced Fujita Scale.

The Enhanced Fujita Scale or EF Scale has six categories from zero to five, with EF5 being the highest degree of damage. The Scale was used the first time as three separate tornadoes took place in central Florida early on February 2, 2007. These tornadoes destroyed many houses and businesses and killed at least 21 people. And these tornadoes were only rated EF3 tornadoes!

Scientists have to figure out how strong a tornado was after it hits. Because the scale is based on the damage caused by it, they can't predict how strong a tornado would be before it happens.

Last modified May 8, 2008 by Jennifer Bergman.

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