Description & Characteristics. Translated from latin meaning hook, the ‘uncinus’ cloud species is found only in the cirrus cloud type. No other cloud type besides a cirrus cloud can be classified as uncinus. Cirrus uncinus cloud formations are a crowd-pleaser and is one of the more well-known cloud type and species combos because of their majestic and distinct look. They’re high in altitude, fibrous in nature, and differ from cirrus fibratus by having more of a curved appearance. The proper cloud classification abbreviation for this cloud is ‘Ci unc’.

Known as mares’ tails and sometimes referred to as comma clouds, cirrus uncinus clouds can predict bad weather in the upcoming 24-48 hours as they might signify an incoming weather front. Cirrus uncinus clouds are often seen in proximation with other cirrus cloud species. It’s also not uncommon to pair the cloud variety radiatus (parallel strips and bands) with a cirrus uncinus cloud if it’s stretched across the sky.

It’s worth noting that cirrus uncinus clouds don’t have that distinct hook-like appearance when viewed from directly beneath them, as they’ll look more tufted and/or fibrous from this angle. As a cloudspotter, keep your eye open for cirrus uncinus clouds… they’re not extremely common, but when you see them over a landscape, they can be very photogenic.