Cumulonimbus calvus is a moderately tall cumulonimbus cloud which is capable of precipitation, but has not yet reached the height where it forms into a cumulonimbus capillatus (fibrous-top) or cumulonimbus incus (anvil-top). Cumulonimbus calvus clouds develop from cumulus congestus, and its further development under auspicious conditions will result in cumulonimbus capillatus. This cloud consists mainly of water droplets.