For a vortex to count as a tornado, it must contact the ground and the cloud base. This definition emphasizes that a tornado is a rotating wind vortex connected both to Earth’s surface and to a cumuliform cloud above. The visible condensation funnel is helpful evidence but is not essential: some tornadoes are hidden by rain, darkness, or low humidity.
The distinction matters because a funnel cloud may hang beneath a storm without producing strong winds at the surface. Once the associated vortex reaches the ground, it meets the usual operational definition of a tornado. Surface debris or damage can reveal a tornado even when no complete visible funnel exists.
A mammatus lobe is a pouch-like cloud feature, a rain shaft is a column of falling precipitation, and an anvil top is the flattened upper spread of a mature thunderstorm. None is the required upper connection in the definition.