Since the end of the Derby has come and gone, it is not the anglers or their escapades that have me pondering poisson. Nor is it the usual seasonal species­—blues, bass, albies and bonito—that have my attention.

Mackerel is on my mind and I am seeing them in the sky, not the sea.

Though fish are not known for flying (or swimming) high above the earth, there is a fishy phenomenon, called mackerel sky that I recently observed. Mackerel sky describes the appearance of a specific cloud formation that resembles fish scales. Also called buttermilk clouds for their curdled appearance and sheep clouds in Germany and France because of their fluffy facade, this atmospheric arrangement is curious and predictive.

Start with the genesis of these scaly sightings, which are made up of rows of cirrocumulus or altocumulus clouds with blue sky in the gaps and seem to flow a distance through the sky. Two types of clouds can produce this spectacle.

Cirrocumulus clouds are one type of tropospheric(lowest region of the atmosphere) clouds. Cirro, means hair locks or tufts, and cumulous, heap, together forming a pretty fair description for these clouds, which are made up of smaller cloudlets consisting of ice or supercooled water. They can have different shapes, including castellanus, floccus, lenticularis and stratiformis, which can be described as turret-like, puffy tufts, lens-shaped and layer-like, respectively.

These clouds are generally regularly spaced and appear as ripples. Cirrocumulus are found at higher altitudes of 5,000 to 12,000 kilometers above the earth’s surface. They form ahead of weather depressions and fronts and indicate a change of conditions and high winds. Precipitation should also be expected in six to twelve hours after seeing these clouds.

The other type of cloud that can create mackerel sky are altocumulus clouds, which are composed of bigger and darker cloudlets made of water droplets, rather than ice. Altocumulus are closer, found from 3,000 to 6,000 kilometers above the earth and are associated with a coming cold front and thunderstorms with rain arriving more quickly, usually within six hours.

Sailors and other weather watchers knew that a mackerel sky would bring a change in weather and a few idioms indicated the coming wet and windy conditions:

Mackerel sky, not twenty-four hours dry.

Mackerel sky, mackerel sky­—never long wet, never long dry.

Mares’ tails and mackerel scales make lofty ships taking in their sails

Mares’ tails and mackerel scales make lofty ships carry low sails

A dappled sky, like a painted woman, soon changes its face.

(Mares’ tail describes another cloudy conundrum where the small cloud poufs have a wind-stretched end).

All the fish in the sky won’t dissuade me from casting for meaning among the atmosphere’s cloudy visage. These airborne formations seem like fish out of water, but keep me hooked on gazing skyward.