noun
anvil cloud
A cumulonimbus cloud whose top has spread into a flat, anvil-like shape, often associated with thunderstorms.
遠くの空にかなとこ雲が見えたら、激しい雷雨に注意が必要だ。
If you see an anvil cloud in the distant sky, be prepared for severe thunderstorms.
Standard kanji-kana mixed spelling for this meteorological term.
Full kanji spelling; less common and may be harder to read.
積乱雲 is the general term for cumulonimbus clouds, while かなとこ雲 specifically refers to the mature stage when the top flattens into an anvil shape.
Compound of 金床 (かなとこ, 'anvil') and 雲 (くも, 'cloud'), from the cloud's resemblance to a blacksmith's anvil.