Arcus clouds


Arcus clouds: low, horizontal cloud formations below the thunderstorm’s rain-free base. The name ‘arcus’ comes from the latin word for ‘arch’. There are two types of arcus clouds: shelf cloud and roll cloud.

Shelf cloud: a shelf cloud is a common type of arcus clouds. It is a low, wedge-shaped, horizontal arcus cloud, attached to the base of the thunderstorm.

Whale’s mouth:

Roll cloud: