Cumulonimbus incus
A cumulonimbus incus cloud, showing the characteristic anvil-top shape the cloud type displays
AbbreviationCb inc.
GenusCumulonimbus (heap, cloud/severe rain)
SpeciesCapillatus (Having hair)
AltitudeGround to 23,000 m
(75,000 ft)
ClassificationFamily C (Low-level)
AppearanceLarge flat-top cloud
PrecipitationVery common rain, snow, snow pellets or hail, heavy at times

A cumulonimbus incus (from Latin incus 'anvil'), also called an anvil cloud, is a cumulonimbus cloud that has reached the level of stratospheric stability and has formed the characteristic flat, anvil-shaped top.[1] It signifies a thunderstorm in its mature stage, succeeding the cumulonimbus calvus stage.[2] Cumulonimbus incus is a subtype of cumulonimbus capillatus. These clouds are commonly associated with severe weather, including heavy rain, downbursts, and occasionally a tornado.


A cumulonimbus incus is a mature thunderstorm cloud generating many dangerous elements.


Cumulonimbus incus over Africa, seen from the International Space Station

Cumulonimbus clouds can be powerful. If the correct atmospheric conditions are met, they can grow into a supercell storm. This cloud may be a single-cell thunderstorm or one cell in a multicellular thunderstorm. They are capable of producing severe storm conditions for a short amount of time.


  1. ^ "Incus".
  2. ^ "Cumulonimbus Incus". EPOD (service of USRA).