arcus cloud
A low, horizontal cloud formation associated with thunderstorms; often appears as a shelf or roll cloud.
アーチ雲は、積乱雲の底にできることが多い。
Arcus clouds often form at the base of cumulonimbus clouds.
気象予報士がアーチ雲の接近を伝えた。
The weather forecaster reported the approach of an arcus cloud.
From English 'arcus' (Latin for 'arch') + 雲 (cloud). The term is a direct loanword compound used in meteorology.