Along with his wife, Sumiko, Fujita introduced the F-scale in a February 1971 paper - Proposed Characterization of Tornadoes and Hurricanes by Area and Intensity. The original Fujita scale contained 6 categories of storms ranging from F0 to F5.
- Wind Speeds of 40-72 mph.
- Mild damages to trees, homes, and signs.
- Also known as a gale tornado.
- Wind Speeds of 73-112 mph.
- Stronger structures show damage. Mobile homes are pushed off their foundations. Vehicles can get pushed off the road.
- Also known as a moderate tornado.
- Wind Speeds of 113-157 mph.
- Significant damages to frame structures. Light objects can become projectiles. Trees can be snapped off or uprooted. Mobile homes are demolished.
- Also known as a significant tornado.
- Wind Speeds of 158-206 mph.
- Homes and businesses severely damaged. Roofs and walls torn off a homes. Trains are overturned and trees in a forest are uprooted or broken. Cars can be tossed into the air.
- Also known as a severe tornado.
- Wind Speeds of 207-260 mph.
- Most homes are leveled. Large objects can become projectiles and the zone of debris increases.
- Also known as a devastating tornado.
- Wind Speeds of 261-318 mph.
- Almost total devastation occurs. Houses can be completely lifted from their foundations. Objects larger than cars can be carried by the funnel and later become dangerous projectiles.
- Also known as an incredible tornado.