Tornado
(Section 3.2.1.5.1)Definition: Tornado: A rotating column of air, extending from the base of a cumuliform cloud, and often visible as a condensation funnel in contact with the ground, and/or attendant circulating dust or debris cloud at the ground.
A large tornado in which the condensation funnel is at least as wide horizontally at the ground as it is in height from the ground to the cloud base may be referred to as a wedge tornado.
During the dissipation stage of a tornado, the condensation funnel will shrink and narrow in width, becoming rope like (a rope funnel), and may also become contorted.
Some tornadoes may contain secondary vortices within the main circulation (suction vortices or subvortices).