Skywatcher Chart

Skywatcher Chart
Mammatus. Clouds with pouch-like downward extensions associated with very active cumulonimbus in latter stages of development. Mammatus occurs when air from the cloud layer descends into the clear air below and the cloud droplets evaporate, cooling down the air and making it descend even faster. Some of the cloud is dragged down, creating the appearance.
Image © For Spacious Skies/John A. Day
