Tornado Scales
The "original" tornado scale was introduced by Ted Fujita in the United States in 1971. This was known as the Fujita Scale (or F-Scale) and was the first attempt to rate the intensity of tornadoes. It was designed to link the Beaufort winds scale with the Mach scale: a Beaufort force 12 was equal to F1 and F12 was equal to Mach 1 (the speed of sound).
 
 
Courtesy: NOAA/ NWS.
In 2007, the enhanced Fujita scale (EF-scale) was adopted in the United States. It was designed to improve the accuracy of wind speed estimates from observed damage by attempting to account for the quality of construction. Canada later adopted the scale in April 2013. 
Courtesy: NOAA/ NWS.
In the UK, we use the T-Scale, or TORRO tornado intensity scale, to rate tornadoes - TORRO is the acronym for the British TORnado and storm Research Organisation. First introduced in 1975, it is intended as an extention of the Beaufort scale, where Beaufort force 8 is T0, force 12 is T2 and (a theoretical) force 28 is T10. 
From : http://www.snipview.com/q/TORRO%20scale