Cumulonimbus incus
Cloud
A cumulonimbus incus, 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. It signifies a thunderstorm in its mature stage, succeeding... Wikipedia
Altitude: Ground to 23,000 m; (75,000 ft)
Appearance: Large flat-top cloud
Precipitation: Very common rain, snow, snow pellets or hail, heavy at times
Species: Capillatus (Having hair)