A rare, mother ship cloud formation hovers over Childress, Texas. Tornado-chasers there covered seven hours and 150 miles (241 kilometers) tracking the supercell thunderstorm that produced this cloud formation. Supercell thunderstorms are known to spawn tornadoes with winds exceeding 200 mph (322 kph).
Arcus clouds come in the shelf or roll variety, and are long, horizontal formations. Shelf clouds are shaped like wedges and roll clouds are shaped like tubes. Both are associated with atmospheric change, but shelf clouds usually bring a thunderstorm.
A shelf cloud is a low, horizontal, wedge-shaped arcs cloud, attached to the base of the parent cloud, which is usually a thunderstorm. The underside often appears turbulent and wind-torn. Cool, sinking air from a storm cloud’s downdraft spreads out across the land surface, with the leading edge called a gust front. This outflow cuts under warm air being drawn into the storm’s updraft.
Mammatus, also known as mammatocumulus (meaning “mammary cloud” or “breast cloud”), is a meteorological term applied to a cellular pattern of pouches hanging underneath the base of a cloud. Derived from the Latin mamma (meaning “breast”).