Starting February 7, 2007 the way Tornadoes are measured will change.  In  1971 Dr. Ted Fujita developed the Fujita Scale to provide a method to rate the intensity of Tornadoes.

The intent of the scale was to distinguish between weak tornadoes and strong tornadoes. There was a need to be able to rate tornadoes in the historical database as well as future tornadoes as they occur. The meteorological and engineering communities almost immediately accepted the Fujita Scale.

Fujita Scale

SCALE	WIND ESTIMATE *** (MPH)	TYPICAL DAMAGE
F0	< 73	Light damage: Some damage to chimneys; branches broken off trees; shallow-rooted trees pushed over; sign boards damaged.
F1	73-112	Moderate damage: Peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos blown off roads.
F2	113-157	Considerable damage: Roofs torn off frame houses; mobile homes demolished; boxcars overturned; large trees snapped or uprooted; light-object missiles generated; cars lifted off ground.
F3	158-206	Severe damage: Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars lifted off the ground and thrown.
F4	207-260	Devastating damage: Well-constructed houses leveled; structures with weak foundations blown away some distance; cars thrown and large missiles generated.
F5	261-318	Incredible damage: Strong frame houses leveled off foundations and swept away; automobile-sized missiles fly through the air in excess of 100 meters (109 yds); trees debarked; incredible phenomena will occur.

The new Enhanced Fujita Scale is a based on Damage Indicators (DI's) and Degree's of Damage (DOD's).  There are 28 different DI's with numerous DOD's per DI. 

For a full description and details of the new EF-Scale, click here for the
EF-Scale Complete Report

Enhanced Fujita Scale (EF-Scale)

SCALE	WIND ESTIMATE *** (MPH) 3-Second Gust
EF0	65-85
EF1	86-110
EF2	111-135
EF3	136-165
EF4	166-200
EF5	Over 200

*** IMPORTANT NOTE ABOUT ENHANCED F-SCALE WINDS: The Enhanced F-scale still 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.

For more details on EF-Scale, visit the Storm Prediction Web site.

For a online training presentation of the new EF-Scale, check out the
National Weather Service Warning Decision Training Branch web site.