part_of part of part of has part has part has_part has quality has quality has member composed primarily of object aggregate water droplet water ice crystal cumulonimbus cloud Cb Cumulonibus-Wolke Gewitterwolke A cloud which 1) has been shaped into dense, mountain-like forms or one or more tower-like forms with a flattened upper portion, which often spreads out in the shape of an anvil or plume, 2) is composed of water droplets and, especially in its upper portion, ice crystals, 3) is located in the low level of the atmosphere (low étage), but can extend into the middle and high level of the atmosphere. Add more PATO qualities once they have been added to PATO. Cumulonimbus clouds have a very dark base which may be merged with low ragged clouds which frequently form underneath this cloud. The upper portion may be smooth, fibrous, or striated. Cumulonimbus also contains large raindrops and, often, snowflakes, snow pellets or hailstones. The water droplets and raindrops may be substantially supercooled. Cumulonimbus is frequently associated with precipitation, sometimes in the form of virga. Cumulonimbus is often accompanied by lightning, thunder or hail. Cumulonimbus usually have their bases in the low level, but their vertical extent is often so great that their tops may reach into the middle and high levels. envoAtmo envoCloudAtlas water-based cloud low atmospheric level middle atmospheric level high atmospheric level cloud top flat increased size increased mass density