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.
Click on image for full size
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.

You might also be interested in:

Science, Evolution, and Creationism

How did life evolve on Earth? The answer to this question can help us understand our past and prepare for our future. Although evolution provides credible and reliable answers, polls show that many people turn away from science, seeking other explanations with which they are more comfortable....more

Tornadoes

Tornadoes form from severe thunderstorms. They have a very high energy density which means that they affect a small area but are very destructive to that area. They also don't last very long which makes...more

Sizes of Tornadoes

Tornadoes come in three different sizes, each with different characteristics. The three sizes are: weak, strong, and violent. Their size is based on how large the tornado is as well as the time that the...more

Wave Beats

Sound travels in waves. You hear sound because waves hit your ear. Sound waves are similar to ocean waves. They both have a certain frequency. The frequency is measured in hertz, which is one cycle per...more

Chasing Tornadoes

Storm chasers are different than storm spotters. Chasers travel around Tornado Alley looking for severe storms and tornadoes. This area in the Great Plains is the best for chasing because of the frequency...more

Energy Density

A tornado is the most intense force in nature. That doesn't mean it's the most powerful. In fact, a thunderstorm can be 40,000 times more powerful than a tornado. Then why aren't thunderstorms as dangerous...more

The Doppler Effect

The Doppler effect was named after Christian Doppler, who first came up with the idea in 1842. He learned that sound waves would have a higher frequency if the source was moving toward the observer and...more

Tornado Forecasts

It's hard to forecast tornadoes. They don't last very long and are also very complicated. Scientists don't really know how they form, but they do where they tend to form. Using what they know about the...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA