The Enhanced Fujita Scale (EF Scale) which became operational on February 1, 2007, is used to assign a tornado a 'rating' based on estimated wind speeds and related damage. ... From that, a rating (from EF0 to EF5) is assigned. The EF scale is a set of wind estimates (not measurements) based on damage. Its uses three-second gusts estimated at the point of damage based on a judgment of 8 levels of damage to the 28 indicators listed below. These estimates vary with height and exposure. Important: The 3 second gust is not the same wind as in standard surface observations. Standard measurements are taken by weather stations in open exposures, using a directly measured, "one minute mile" speed. EF-O 65 TO 85mph Winds Minimal Damage likely EF-1 86 to 110mph Winds Moderate Damage EF-2 111-135mph Winds Considerable Damage Likely EF-3 136-165mph Winds Severe Damage likely with an EF-3 EF-4 166-200mph Winds Catastrophic Severe Damage Likely with an EF-4 EF-5 over 200mph Winds Catastrophic Extreme Damage Likely with an EF-5
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