What are the scales used for measuring tornadoes strength?

Answer 1

There are three scales for measuring tornado strength, all of which use damage to estimate wind speed.

The first and most famous is the Fujita scale, developed in 1971. This scale rates tornadoes from F0 at the weakest to F5 at the strongest. Most countries that take the time to rate their tornadoes use this scale.

The next scale to be creates is the TORRO scale, developed in 1975 which runs from T0 at the weakest to T11 at the strongest. There are two TORRO categories for every Fujita category, for example a T0 or T1 tornado is equivalent to an F0 while a T10 or T11 is equivalent to an F5. This scale is used in only a few European nations.

Finally there is the Enhanced Fujita scale developed in 2007.It runs from EF0 to EF5. This scale was derived from the Fujita scale and provides more accurate wind speed estimates than the original scale, particularly where the original wind estimates for F3 and stronger tornadoes were far too high. Currently this scale is only used in the United States, though Canada plans to adopt the scale in 2013. All U.S. tornadoes prior to February of 2007 and all Canadian tornadoes prior to 2013 retain their original Fujita ratings.