<Tr> <Th> Appearance </Th> <Td> Very tall and large clouds </Td> </Tr> <Tr> <Th> Precipitation cloud? </Th> <Td> Yes, often intense </Td> </Tr> <P> Cumulonimbus, from the Latin cumulus ("heap") and nimbus ("rainstorm", "storm cloud"), is a dense towering vertical cloud associated with thunderstorms and atmospheric instability, forming from water vapor carried by powerful upward air currents . If observed during a storm, these clouds may be referred to as thunderheads . Cumulonimbus can form alone, in clusters, or along cold front squall lines . These clouds are capable of producing lightning and other dangerous severe weather, such as tornadoes . Cumulonimbus progress from overdeveloped cumulus congestus clouds and may further develop as part of a supercell . Cumulonimbus is abbreviated Cb . </P> <P> Towering cumulonimbus clouds are typically accompanied by smaller cumulus clouds . The cumulonimbus base may extend several miles across and occupy low to middle altitudes - formed at altitude from approximately 200 to 4,000 m (700 to 10,000 ft). Peaks typically reach to as much as 40,000 ft (12,000 m), with extreme instances as high as 70,000 ft (21,000 m) or more . Well - developed cumulonimbus clouds are characterized by a flat, anvil - like top (anvil dome), caused by wind shear or inversion near the tropopause . The shelf of the anvil may precede the main cloud's vertical component for many miles, and be accompanied by lightning . Occasionally, rising air parcels surpass the equilibrium level (due to momentum) and form an overshooting top culminating at the maximum parcel level . When vertically developed, this largest of all clouds usually extends through all three cloud regions . Even the smallest cumulonimbus cloud dwarfs its neighbors in comparison . </P>

What is the difference between cumulus and nimbus clouds