The Parkersburg, IA tornado

On May 25, 2008, a large and destructive tornado moved across Butler and Black Hawk Counties in Iowa striking the south end of the town of Parkersburg. The tornado damaged or destroyed more than one hundred residences in addition to two bank buildings, a high school, and other buildings. Seven people lost their lives. The damage path was up to four blocks wide in town but was wider farther to the east in rural areas. Aerial and ground surveys were conducted. Tornado damage intensity was rated according to the new EF-scale, adopted by the National Weather Service in February 2007. Maximum damage intensity was EF-5 with three-second wind gusts around 92 m/s. This paper will present how the EF-scale ratings were determined from the analysis of building damage.