Cumulus clouds with considerable vertical growth in the form of rising mounds, domes or towers. They are of great vertical extent; their bulging upper part frequently resembles a cauliflower. The sunlit parts of these clouds are mostly brilliant white; their base is relatively dark and nearly horizontal.
Towering Cumulus is an aviation specific cloud description. It is itself a subdivision of the Cumulus genus. WMO technical notes describe Towering Cumulus as Cumulus congestus of great vertical extent.
Distinguishing TCu from other genera
Towering Cumulus differs from Cumulonimbus in that the sprouting upper parts are sharply defined throughout, with no fibrous or striated texture apparent. Towering Cumulus is not accompanied by lightning and thunder.
Towering Cumulus is distinguished from Cumulus by its greater vertical extent. There is no internationally agreed criteria for TCu but the following guides can be useful:
- The cloud will be at least 10000 feet tall from base to top; or
- The height of the cloud is at least twice its width.
A continuous weather watch will sometimes reveal the transformation from Cumulus to Towering Cumulus to Cumulonimbus.
Precipitation in the form of showers of rain, snow, or snow pellets may occur with Towering Cumulus.