NASHVILLE, Tenn. (WSMV) – If you looked up over Middle Tennessee this morning and saw the sky covered in ripples that looked like fish scales, you witnessed what’s known as a ‘mackerel sky’.
A mackerel sky forms when mid-level clouds — usually altocumulus — line up in rows across the sky. Altocumulus clouds form in the middle layer of the atmosphere when moisture is present.
As gravity waves move through the moist layer, it causes puffy cumulus clouds of roughly the same size to form. They are called a ‘mackerel sky’ because the pattern often resembles that of scales on a fish…