cap cloud
A lens-shaped cloud that forms over a mountain peak, resembling a traditional Asian bamboo hat (笠). Used in meteorology and mountain descriptions.
It is said that when a cap cloud forms over Mt. Fuji, the weather will turn bad.
Cap clouds are formed by strong winds near the mountain summit.
Compound of 笠 (かさ, 'bamboo hat') and 雲 (くも, 'cloud'), from the cloud's resemblance to a traditional hat sitting on a mountain peak.