An area of upper level low pressure moved across the Great Lakes, with a trough extending into the Ohio Valley. The airmass had become unstable, and shear in the low levels of the atmosphere became favorable for the formation of tornadoes. In addition, thunderstorms tended to rebuild over the same areas, and rainfall was very heavy. This led to flash flooding across the region as well.
Brown/Highland County Tornado:
Location: near Mount Orab, Ohio Time: 644 PM EDT, May 21, 2010 EF Rating: EF1 Maximum Winds: 100 MPH Path Width: 50 yards Path Length: 3 miles
The National Weather Service in Wilmington OH has confirmed a tornado near Mount Orab in Brown and Highland Counties of Ohio, on May 21, 2010. The tornado touched down in the vicinity of Highway 32 and Klein Road in Brown County, and crossed into Highland County before lifting near Highway 321 southeast of Buford. The worst damage occurred to a residence on Sicily Road in Highland County, which was rated EF1 damage (estimated wind speeds of 100 mph) due to a section of roofing removed from parts of the home, the front porch supports lifted and removed, numerous uprooted trees, and a 2x4 driven into decking material. Several other barns and outbuildings were destroyed or heavily damaged along the path. Witness accounts indicate there may have been two tornadoes on the ground at the same time, though damage assessment could not confirm this.
Location: near Bentonville, Ohio Time: 844 PM EDT, May 21, 2010 EF Rating: EF1 Maximum Winds: 110 MPH Path Width: 75 yards Path Length: 2.6 miles
The National Weather Service in Wilmington OH has confirmed a tornado near Bentonville in Adams County of Ohio, on May 21, 2010. Information from residents along Old Dutch Road revealed a fairly continuous tornado track of 2.6 miles in Adams County. The tornado initially touched down approximately 844 PM just north and east of the intersection of Old Dutch Road and Gray Road (Township Highway 185). The tornado moved north along Old Dutch Road, heavily damaging several well constructed barns and outbuildings. Mature, healthy trees were snapped at the trunk along this path. The tornado crossed Stanfield Road (Township Highway 326) and apparently crossed Old Dutch Road near its intersection with Clayton Pike (County Road 3). Along this stretch, the tornado caused significant tree damage, minor damage to homes, and the significant damage to numerous barns and outbuildings mentioned above. More trees were toppled as the tornado crossed Clayton Pike again, west of Old Dutch Road. At this point it appears the tornado began to intermittently lift, with the next reportable damage on neighboring Suck Run Road. Damage here was limited to windows being blown out of a home, and significant tree damage strewn about the property in various orientations. This is corroborated by several reports of a tornado touchdown in this area, and a strong radar signature of circulation. The damage to barns and trees is consistent with the upper limits of EF1 wind speeds (about 110 MPH).