This section explains terminology that will help you better understand tornado-related events in Historical Weather Risk.
Funnel cloud
A violent, rotating column of air visibly extending from the base of a towering cumulus or cumulonimbus cloud toward the ground, but not in contact with it. Funnel clouds produce no detectable debris or damage at ground level.
Multiple vortex tornado
A tornado that has two or more condensation funnels or debris clouds, often rotating around a common center. The subvortex can add over 100 MPH to the relative ground wind speed of the tornado. Multiple vortex tornadoes are responsible for most cases in which narrow arcs of extreme destruction are seen next to areas of weak damage along tornado paths.
Waterspout
A small, weak tornado which is not formed by storm-scale rotation. A waterspout is generally weaker than a supercell tornado and is not associated with a wall cloud or mesocyclone. It may be observed beneath cumulonimbus or towering cumulus clouds. Waterspouts are common along the southeastern coast of the United States but can occur over any body of water. Waterspouts can overturn small boats, damage ships, and cause significant damage if they come ashore.