Definition

A funnel cloud, similar to a Tornado, which projects below a cloud over water.

Discussion

Waterspouts are similar to tornadoes in structure but occur over the sea rather than over the land and are not usually associated with a mid level (Mesocyclone) rotation within the parent Cumulus/Cumulonimbus (Cb) cloud. They are believed to be produced along surface airmass convergence boundaries. As the parent cumulus cloud develops in intensity, so the potential for a waterspout increases. Surface spray may be seen at the base of the waterspout yet, until the wind speed in the vortex reaches about 35 kts, the waterspout may not be visible. A fully developed waterspout will be quite distinctive with the funnel filled with water droplets.