Rotating clouds: wall clouds, funnel clouds and mesocyclones

Much of eastern Ohio and western Pennsylvania had a few rounds of storms on Wednesday, and one storm in particular produced some vivid clouds over parts of the region. We received lots of pictures and videos from area residents that showed low-hanging clouds that appeared to be rotating. 

It is important to note that there were no tornadoes across our region on Wednesday. 

One storm did trigger a couple of tornado warnings as it moved through parts of the Rt. 224 corridor and then eventually northeastern Columbiana County. The storm was a somewhat rare one for our part of the country: a true "supercell" thunderstorm. Supercells are strong, often isolated thunderstorms that frequently rotate and produce sizeable hailstones.  They are more common in the Plains states and the Southeast. The Upper Ohio Valley and southern Great Lakes sees clusters of storms and squall lines with more frequency than true supercells. 

Meteorologists look for signs of rotation on weather radars by looking for "couplets": areas where the wind is blowing in one direction in close proximity to winds blowing in the opposite direction. Wednesday's supercell exhibited signs of rotation during much of it's lifecycle; sometimes the rotation looked rather weak and other times it appeared to be stronger. The episodes of strongest rotation triggered the Tornado Wanings from the National Weather Service.

A rotating thunderstorm is often referred to as a "mesocyclone". What many photographers captured Wednesday was a lowering of the cloud base, or a "wall cloud". A wall clouds sometimes is a precursor to the birth of a tornado. Often times, like in the case of Wednesday's storm, the rotation at the cloud level does not extend all the way to the ground and no tornado occurs.