A vocabulary of landscape — a landscape of words
975 entries
arcus
A dense horizontal roll of cloud on the lower leading edge of a storm, ragged underneath, reading as a long dark arch when it stretches across the sky. It comes two ways. A shelf cloud is attached to the base of the parent cumulonimbus and forms where cold outflow shovels warm moist air upward. A
Etymology
Latin arcus, a bow or an arch — the same word behind arc, arch, and archer.
Notes
The most famous roll clouds on earth are the Morning Glory of the Gulf of Carpentaria in northern Australia, which arrives with enough regularity in September and October that glider pilots travel there to fly it.