The second severe event in the series was certainly atypical for the Ohio Valley. The warm frontal boundary which stretched across the area acted as a source of convergence, and thunderstorms rapidly developed in the unstable air mass just after 6:30 PM. Many of the storms became legitimate, well-organized supercells -- resembling the intense storms more often seen in the plains. The storms themselves moved east-southeast, as the line slowly drifted northward. Many of the storms exhibited signs of rotation, and the NWS in Wilmington received literally dozens of funnel cloud reports over the course of the evening. A few reports of large hail were also received.
In the end, only two weak tornadoes were confirmed, despite radar imagery which may have suggested a more significant outbreak. It appears that the wake of the severe event earlier in the afternoon left a very shallow layer of stable air near the surface. This likely contributed to the inability of the funnel clouds to reach the ground. It also contributed to the fact that virtually no wind damage was reported from these storms.
At around 9:00 PM, one supercell thunderstorm moved just a few miles north of the Wilmington NWS office. Through flashes of lightning, a ragged wall cloud was visible.
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At 9:06 PM, reflectivity data (left) indicated a classic-looking supercell thunderstorm over northwestern Butler County, Ohio. The hook echo in the far corner of the county is one indication of the storm's organization. Storm relative motion data (right) indicated inbound winds (green) and outbound winds (red) in close proximity. This couplet is a tell-tale sign of a strong circulation in the lower levels of the atmosphere. At around this time, a tornado touched down near Oxford.
Although the proximity to the radar makes it difficult to see, this frame from around 12:25 AM shows a smaller supercell thunderstorm over Clinton County. The reflectivity data (left) does indicate somewhat of a hook echo here as well. The circulation in the storm relative motion data (right) is much easier to see. A weak tornado touched down near Martinsville at around this time.
