“A cumulonimbus incus (Latin incus, “anvil”) is a cumulonimbus cloud which has reached the level of stratospheric stability and has formed the characteristic flat, anvil-top shape. It can cause a supercell and then a tornado.
A cumulonimbus incus is a mature thunderstorm cloud and can produce many dangerous elements.
Lightning; this storm cloud is capable of producing bursts of cloud to ground lightning.
Hail; small hail balls may fall from this cloud.
Heavy rain; the cloud may drop several inches of rain in a short amount of time. This could cause flash flooding
Strong wind; gale force winds from a downburst may occur under this cloud."