Storm Glossary Accessory Clouds Clouds that are dependent on a larger cloud system for development and continuance.
Accessory clouds associated with the thunderstorm include roll, shelf, mammatus, and wall clouds.
The spreading of the upper portion of a cumulonimbus cloud into an anvil-shaped plume usually of fibrous or smooth appearance. Strong or severe thunderstorms often have thicker anvils with the side and bottom having a cumuliform or slowly boiling appearance in the immediate vicinity of the parent cumulonimbus. Collar Cloud Frequently used as a synonym for wall cloud, although it actually is a generally circular ring of cloud surrounding the upper portion of a wall cloud. The parent cloud of a thunderstorm. The cloud's upper portion includes the anvil.