EXPLAINER: What is the EF scale when talking about tornadoes?

OMAHA, Neb. (WOWT) - After a tornado event, the National Weather Service sends out teams to survey the damage and classify tornadoes using the Enhanced Fujita Scale.

The scale ranges from EF-0 to EF-5, an EF-5 being the most destructive level of tornado. The categories are based off of estimated wind speed determined by the level of damage. The scale does not take the tornado’s size, duration, or radar wind speeds into account.

The EF Scale replaced the original F scale in 2007 and has been used ever since. The EF Scale takes more variables into account when determining a wind speed rating for a tornado. It uses three-second estimated gusts based on 28 damage indicators with up to 12 degrees of damage for each indicator.

The 28 damage indicators range from small barns and farm outbuildings to high-rise buildings. Damage assessors will also take into account how the buildings were constructed, such as if they were anchored to the foundation and if they were up to code, or what codes were used when the building was constructed.

The reason why wind speeds are estimated off of damage and not based on recorded observations or radar is because wind speeds that strong can damage any unprotected instruments, and radar doesn’t represent ground conditions. Because of this, there must be damage in order to rate a tornado.

An EF-0 tornado can be attributed to estimated wind gusts between 65-86 mph, power outages, large branches broken, shingles peeled off of homes, and damage to gutters and siding.

With an EF-1 tornado, power poles may be knocked down, small trees uprooted, with significant roof damage and broken windows with estimated wind gusts between 86-110 mph.

Damage such as powerlines down, cars flipped, large trees uprooted and whole sections of roofs ripped off falls under the category of an EF-2 tornado. Estimated wind gusts for this rating are between 111-135 mph.

An EF-3 tornado has estimated wind speeds between 136-165 mph. Most standing objects will be knocked over, trees severely damaged, vehicles moved, top floors of homes ripped off, and outer walls of structures knocked down.

Damage associated with an EF-4 includes cars tossed into the air, landscaping ripped out, and all exterior walls of a well-built home destroyed. Estimated winds for an EF-4 are between 166-200 mph.

An EF-5 is the highest level of damage attributed to a tornado with wind speeds over 200 mph. This level of tornado will sweep well built homes from their foundation, peel concrete and grass from the ground, and completely destroy areas that it crosses. The last EF-5 tornado was in Moore, Oklahoma in May of 2013.

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