Currently, there is no way to exactly determine just how fast tornado winds blow. Even though scientists and researchers can now gather wind speed measurements with mobile Doppler radars and other equipment, the data they gather is taken from some distance, so cannot be taken as exact. Instead, scientists estimate a tornado's maximum winds based on the damage left behind. A damage scale, developed by renowned tornado researcher Dr. Theodore Fujita, ranks tornadoes from F0, the weakest, to F5, the strongest. Click on the image above to see examples of the associated damage.

After a devastating tornado tore through Oklahoma City, Okla., on May 3, 1999, some debate ensued as to whether it surpassed the highest rating of F5 on the Fujita scale and was actually an F6. Tornado researchers, using a mobile Doppler radar, measured winds within the twister at 318 mph, the upper threshold of an F5.

"With the preliminary DOW (Doppler On Wheels) measurement of 318 mph, it was natural for people to wonder if speeds might have reached 319 (F6) or higher," Dr. Greg Forbes, Severe Weather Expert at The Weather Channel, said.

"But then people also realized that the tornado intensity rating applies to winds at the house level instead of the higher height of the radar beam. Since winds in a tornado decrease toward the ground, F5 made sense and matched the damage."

Researchers say that it is unlikely that the Fujita scale will ever be revised to include an F6 ranking unless reliable wind speed measurements decidedly above 318 mph are obtained close to the ground.