Friday, August 09, 2013

Tornado Confirmed in Orrville, Ohio

The National Weather Service confirmed that the damage from severe storms Wednesday afternoon in Orrville, Ohio WAS from a tornado. Estimated maximum wind speed: 95 mph; Maximum path width: 50 yards; path length: 1 mile.

There is a misconception that tornado wind speeds are estimated from doppler radar or some other direct measurement. Wind speeds are "reverse engineered" by surveying damage. The estimated wind speed is the--and this is key--AN ESTIMATED THREE-SECOND GUST AT THE POINT OF DAMAGE.

The type of structure/tree is assigned one of the 28 Indicators that describe the type of structure. DEGREES OF DAMAGE (scale of 1 to 9) are assigned to each indicator. After the assessment for all indicators is complete, the estimated three second wind speed is determined. A more detailed EF Powerpoint is provided by the National Weather Service.

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