Tetsuya Theodore "Ted" Fujita (1920-1998) developed the original Fujita Tornado Intensity Scale. The scale was changed to the “Enhanced” Fujita Scale in 2007, after more information about the destructiveness of tornadoes had been scientifically examined. The estimated wind speeds were updated, and more specific damage requirements were set. Tornadoes are now measured AFTER damage has been assessed, days after a tornado strikes.
The size of a tornado is not necessarily a measure of its intensity. Larger tornadoes can be weaker and less violent than smaller tornadoes that have more intense winds. Tornadoes in the EF0-EF2 range are much more likely to develop than stronger ones, but all tornadoes can be deadly. Following these tips could save your life.