HOW TO MEASURE A TORNADO

The original FUJITA SCALE (or F Scale) was developed by Dr. Theodore Fujita to classify tornadoes based on wind damage. All tornadoes, and other severe local windstorms, were assigned a number according to the most intense damage caused by the storm. An enhanced F (EF) scale was implemented in the United States on February 1, 2007. The EF scale uses 3-second gust estimates based on a more detailed system for assessing damage, taking into account different building materials.

F SCALE   EF SCALE (U.S.)

F0 • 40–72 mph (64–116 km/h) LIGHT DAMAGE EF0 • 65–85 mph (105–137 km/h)

F1 • 73–112 mph (117–180 km/h) MODERATE DAMAGE EF1 • 86–110 mph (138–178 km/h)

F2 • 113–157 mph (181–253 km/h) CONSIDERABLE DAMAGE EF2 • 111–135 mph (179–218 km/h)

F3 • 158–207 mph (254–332 km/h) SEVERE DAMAGE EF3 • 136–165 mph (219–266 km/h)

F4 • 208–260 mph (333–419 km/h) DEVASTATING DAMAGE EF4 • 166–200 mph (267–322 km/h)

F5 • 261–318 mph (420–512 km/h) INCREDIBLE DAMAGE EF5 • over 200 mph (over 322 km/h)

Wind/Barometer Table

NOTE: A barometer should be adjusted to show equivalent sea-level pressure for the altitude at which it is to be used. A change of 100 feet in elevation will cause a decrease of 1⁄10 inch in the reading.