Incus

Definition

A supplementary cloud feature of cumulonimbus consisting of the flattened, broad top of the cloud, shaped like an anvil and made largely of ice crystals. Its presence marks a cumulonimbus in or past its mature stage.

Field note

An anvil that is growing quickly downwind means a strong storm; a storm that is all anvil with no tower beneath it is dissipating. The exception is a storm generating new towers continuously on its upwind flank.

Related terms

• Cumulonimbus · Cumulonimbus
• Mamma (mammatus) · mamma
• Congestus · congestus