After two days of ground and aerial damage surveys, the National Weather Service has concluded much of the state was impacted by 60 to 70 mph straight line winds with three imbedded tornadoes. The tornadoes were all rated F1 on the Fujita scale. The delay in finalizing the storm assessment is due to the size of the area impacted. The confirmed tornadoes were in the town of Mitchell in Lawrence County, Seymour in Jackson County, and southeast of Romney in Tippecanoe County. Winds of 100 mph or more also caused significant damage in Indianapolis and Washington in Daviess County.
“The storm that impacted central Indiana Sunday night was a derecho.” said John Ogren, Meteorologist in Charge of the National Weather Service in Indianapolis. A derecho is a widespread and unusually fast-moving thunderstorm complex producing damaging straight-line winds over hundreds of miles. They can also produce small tornadoes within the high wind areas. “The difficulty in surveying damage after a derecho is that often times the tornado damage is masked by the larger area of high wind damage.”
The decision to rate the damage in Indianapolis and Washington as extreme wind damage versus tornado damage was based on the fact that the preponderance of evidence pointed to straight line winds. “This is exactly why people need to heed severe thunderstorm warnings as much as tornado warning”, said Ogren. “They can clearly do as much or more damage than weak tornadoes”.
Damage pictures are below. Click to see a large version: