Aileron

METAR code: CBMAM

Latin for "giant thundercloud with tits", these are generally seen in the aftermath of very severe thunderstorms, although can also act as harbingers before the storm. The lobes are typically 1–3 km in diameter and can consist of both ice and water. Unclear exactly how they form, but they're not something you want to see while flying as severe wind shear and tornadic activity may be nearby.

Photo: Craig Lindsay