innocuous as a moderate cumulus, or as significant as a thunderstorm. Waterspouts normally develop as their parent clouds are in the process of development, and it is theorized that they spin up as they move up the surface boundary from the horizontal wind shear near the surface, and then stretch upwards to the cloud once the low level shear vortex aligns with a developing cumulus or thunderstorm. Weak tornadoes, known as landspouts, across eastern Colorado have been witnessed to develop in a similar manner. An outbreak occurred in the Great Lakes in late September and early October 2003 along a lake effect band. September is the peak month of landspout and waterspout occurrence around Florida and for waterspout occurrence around the Great Lakes. Related terms Cyclogenesis is the opposite of cyclolysis, which concerns the weakening of surface cyclones. The term has an anticyclonic (high-pressure system) equivalent—Anticyclogenesis, which deals with the formation of surface high-pressure systems. See also Atmospheric river European windstorm Hurricane dynamics and cloud microphysics Hybrid low Surface weather analysis Miller Classification Notes References Atmospheric dynamics Synoptic meteorology and weather