Rating Tornadoes

Tornadoes are one of the most violent and destructive type of storms in the United States. They can develop suddenly with winds speeds rotating as fast as 300 miles per hour.

In 1971, Dr. T. Theodor Fujita developed a scale to rate the destructiveness of tornadoes. In February, 2007, meteorological experts modified the scale and created a more comprehensive rating system called the Enhanced Fujita Scale (EF Scale).

The National Weather Service uses the Enhanced Fujita Scale to rate the intensity of a tornado using a combination of the amount of destruction and wind speeds. The scale contains six levels with guidelines for determining damage (damage indicators).

EF Scale Levels

EF0 tornadoes have estimated wind speeds between 65 and 85 miles per hour. These tornadoes cause minor or no damage. Minor damage can include damage to gutters and siding, broken branches, small or shallow trees uprooted and confirmed tornadoes with no reported damage. 53.5% of all tornadoes are rated EF0.

EF1 tornadoes have wind speeds between 86 and 110 miles per hour which is approximately the same as a Category 1 or 2 hurricane. EF1 tornadoes produce moderate damage such as mobile homes pushed off foundations or overturned, roof surface peeled from homes, missing exterior doors and broken windows. 31.6% of all tornadoes fall in the EF1 range.

EF2 tornadoes have wind speeds between 111 and 135 miles per hour. An EF2 tornado can cause considerable amount of damage to roofs, demolish mobile homes, large trees uprooted, cars lifted off the ground and light objects become missiles. EF2 tornadoes occur 10.7% of the time.

EF3 tornadoes cause severe damage with wind speeds between 136 and 165 miles per hour, the same as a Category 4 hurricane. Destruction includes damage to entire homes, severe damage to large buildings, trains overturned, and heavy vehicles lifted off the ground. It’s believed that 3.4% of all tornadoes fall in the EF3 range.

EF4 tornadoes cause extreme damage. Winds speeds reach from 166 to 200 miles per hour, the same as a Category 5 hurricane. This devastating tornado will completely level homes. damage to commercial buildings and large objects will be thrown about. Only 0.7% of all tornadoes are rated as EF4.

EF5 tornadoes are capable of total destruction to commercial and residential buildings. Wind speeds are in excess of 200 miles per hour. Tall buildings will collapse and homes will be blown away. Less than 0.1% of all tornadoes are classified at the EF5 level.

Many people mistakenly believe the larger the funnel cloud the more powerful the tornado. This is simply not true. Large tornadoes can be weak and small tornadoes can be violent. The EF Scale is based on wind speeds and damage, not the appearance or size of the funnel cloud. The only way to officially categorize a tornado is after it has passed. Personnel from the National Weather Service will survey the damage and assign an EF-Scale rating.