Tornadoes and Tornadic Storms

Abstract

Tornadoes, with measured wind speeds of 125 m s−1 to perhaps 140 m s −1, are the most violent of atmospheric storms (Fig. 5.1). A tornado is defined here as a violently rotating, narrow column of air, averaging about 100 m in diameter, that extends to the ground from the interior of a cumulonimbus (or occasionally a cumulus congestus) cloud and appears as a condensation funnel pendant from cloud base and/or as a swirling cloud of dust and debris rising from the ground. Significant damage can occur at the ground even when the condensation funnel does not reach the surface. A condensation funnel associated with a tornadic vortex that fails to contact the ground is called a funnel cloud. A waterspout is a tornado over a body of water.