The Fujita Scale has been adopted worldwide as a numerical indicator of the size of tornadoes. It was devised by the late Tetsuya Fujita, a meteorologist known as “Dr. Tornado.” The size of typhoons can be expressed by their wind speeds or atmospheric pressure, but in the past there was no such way to express the size of tornadoes. In the early 1970s, thinking that changes caused in houses and natural objects by tornadoes could play a role in measuring them, Fujita developed criteria to estimate the force and size of tornadoes from the damage they caused. The resulting Fujita Scale is a 6-level scale, with rankings from F-0 to F-5.