Cloud symbol CL 3. Cumulonimbus, the summits of which, at least partially, lack sharp outlines but are neither clearly fibrous (cirriform) nor in the form of an anvil; cumulus, stratocumulus or stratus may also be present (cumulonimbus calvus).
This file was derived from: CL 3.png (http://www.srh.noaa.gov/srh/jetstream/clouds/cloudchart.htm see linked subpages by NOAA)
Actam