What Is Arcus Cloud?
A low, horizontal, often shelf-shaped cloud on the front edge of a storm's cool outflow. It can look menacing but is not itself a tornado. In technical terms: A dense, horizontal roll or shelf-shaped accessory cloud attached to (shelf cloud) or detached from (roll cloud) the lower leading edge of a cumulonimbus, formed by lifting of warm moist air over an advancing gust front.
Also called: Shelf Cloud, Roll Cloud
Arcus Cloud In Plain English
A low, horizontal, often shelf-shaped cloud on the front edge of a storm's cool outflow. It can look menacing but is not itself a tornado.
The Technical Definition
A dense, horizontal roll or shelf-shaped accessory cloud attached to (shelf cloud) or detached from (roll cloud) the lower leading edge of a cumulonimbus, formed by lifting of warm moist air over an advancing gust front.
