(WHSV) - When it comes to determining the strength of a tornado, we use the Enhanced Fujita Scale (EF) to rate the damage. This was orginally known as just the Fujita Scale (F) but in 2007, that changed to the EF scale which more accurately characterized damage.

Tornadoes are not measured as they happen. It takes surveyers to look at the damage to determine what wind speed could have caused the destruction. Also, they need to differeniate whether the wind damage was caused by a tornado or just straight line winds.

THE SCALE:

EF-0: EF-0′s are the weakest tornadoes. An EF-0 tornado has max wind speeds of 65-85 mph. Typically with an EF-0, damages include shingles or portions of a roof peeled off, gutter and siding damage, branches broken off trees, and trees that are shallow rooted being toppled.

EF-0 tornadoes can be weaker than straight line wind damage. The tornado that touched down near the town of Fairfield in Rockbridge County last Friday actually had weaker winds then the straight-line winds that went through the area.

EF-1: These tornadoes have max wind speeds of 86-110 mph. Typically with these tornadoes, there is significant roof damage, broken windows, exterior door damage, and mobile homes begin toppled over or severely damaged. The Augusta County tornado last month was an EF-1.

EF-2: EF-2 tornadoes cause considerable damage. They have wind speeds of 111-135 mph. This is enough to tear roofs compeletely off, knock homes off their foundation, completely destroy mobile homes, snap large trees and even pick up and toss vehicles.

EF-3: This is where we really start to get really bad tornadoes. Wind speeds at this rating are 136-165 mph which causes severe damage. Damages at this level include stories of houses completely destroyed, significant damage to large builidings, homes on weak foundations being blown away, and bark actually getting ripped from trees.

EF-4: Tornadoes at this level are not common at all. Out of all tornadoes that have touched down in recorded history, only 1 percent of tornadoes have been EF/F-4 or stronger. Having wind speeds of 166-200 mph, these tornadoes level well-built homes, throw cars a significant distance, and collapse walls of masonry buidlings.

EF-5: These tornadoes are very rare and are catastrophic. Wind speeds of an EF-5 are 200 mph or greater. The last time we had an EF-5 tornado in the United States was back in 2013. Damages at this level include homes being swept away, steel-reinforced concrete structures and high-rise buildings being severly damaged, and trees stripped entirely of their bark and branches or compeletly snapped.

OTHER TORNADO FACTS

The strongest tornado the United States has ever seen was a tornado that touched down near Oklahoma City on May 3rd, 1999. This tornado had max wind speed estimated at 302 mph!

Since 1950, the state of Virginia has not seen an EF/F-5 tornado and only 2 of EF/F-4 level. One occured on August 6th, 1993 touching down near Petersburg, VA. The second one on September 24th, 2001 near the town of Rixeyville in Culpeper County.

In our area, we have seen 2 EF/F-3 level tornadoes. Both were in Albemarle County (1959 and 1985). We have also seen 9 EF/F-2 tornadoes with the last one occuring April 28th, 2011. This was the long track tornado that was on the ground for 33 miles in Rockingham and Shenandoah County.

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