Cumulonimbus incus

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Cumulonimbus Incus
Cumulonimbus Incus
Cumulonimbus Incus
Abbreviation Cb inc.
Genus Cumulonimbus (heap, cloud/severe rain)
Species Capillatus (fibrous)
Classification Family D (Vertically developed)
Appearance Large flat-top cloud
Precipitation cloud? Yes, often intense

A cumulonimbus incus (Latin incus, "anvil") also known as an anvil cloud is a cumulonimbus cloud which has reached the level of stratospheric stability and has formed the characteristic flat, anvil-top shape. They can form into supercells resulting in severe storm phenomena such as tornadoes, flash flooding and downbursts. The cumulonimbus incus is formed when the updraft is strong and vigorous. They form from cumulonimbus calvus which have puffy tops. A cumulonimbus incus means that the thunderstorm is in its mature stage and it may bring severe weather. So if a cumulonimbus incus is sighted, people in its path must take shelter immediately to protect themselves from multiple severe weather threats.

Cumulonimbus capillatus is a sub-form of cumulonimbus incus.


A cumulonimbus incus is a mature thunderstorm cloud and it can produce many dangerous elements.

  • Lightning; this storm cloud is capable of producing bursts of cloud to ground lightning.
  • Hail; hailstones may fall from this cloud if it is in a highly unstable environment (which favors a more vigorous storm updraft).
  • Heavy rain; the cloud may drop several inches of rain in a short amount of time. This can cause flash flooding
  • Strong wind; gale force winds from a downburst may occur under this cloud.


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