Arcus Cloud

weather · clouds · thunderstorms · sky

Two main types. Arcus clouds come in two forms: roll clouds, which look like a spinning cylinder, and shelf clouds, which appear as a flat ledge hanging from the sky.

Storm chasers' favorites. These clouds form right at the leading edge of thunderstorms and derecho systems, where cold air rushes forward and creates dramatic, sculptured formations that are thrilling to watch.

Cold air rising. Arcus clouds form when cold air from a storm's gust front meets warmer air above it, causing the air to lift and create these distinctive low, horizontal shapes.

Also appear at sea. Roll clouds can form even without thunderstorms, appearing along cold ocean breezes and cold fronts where cold air slides beneath warmer air in the sky.

Super photogenic. These clouds are among the most dramatic weather formations visible from the ground, with bold lines and sculptured shapes that make them popular with weather photographers and storm chasers.