Cirrocumulus clouds

What are cirrocumulus clouds?

Cirrocumulus clouds are made up of lots of small white clouds called cloudlets, which are usually grouped together at high levels. Composed almost entirely from ice crystals, the little cloudlets are regularly spaced, often arranged as ripples in the sky.

Cirrocumulus can sometimes appear to look like the scaly skin of a fish and are sometimes referred to as a "mackerel skies".

How do cirrocumulus clouds form?

Cirrocumulus cloudlets are usually made up of both ice and 'supercooled' water, this means that water remains a liquid, even at temperatures well below 0oC. They form when turbulent vertical currents meet a cirrus layer, creating the puffy cumulus shape.

Cirrocumulus clouds can also form through contrails, the vapour trails left by planes as they fly through a dry upper troposphere. These streaks can spread out and become cirrus, cirrostratus and cirrocumulus.

What weather is associated with cirrocumulus clouds?

Precipitation from cirrocumulus clouds never reaches the surface, meaning that these clouds are usually associated with fair-weather. However their appearance can often prelude stormy weather meaning you should make the most of the sun while you still can.

How do we categorise cirrocumulus clouds?

Cirrocumulus clouds have four defined 'species', which describe its appearance;

• Cirrocumulus stratiformis - Flat sheets or patches of cirrocumulus with fine separation leading to a fish scale like appearance
• Cirrocumulus lenticularis - High level icy lenses, similar to Lenticular clouds but much less common. These are often larger than the usual altocumulus cloudlet, with a rounded shape
• Cirrocumulus floccus - Fluffy tufts of cirrocumulus, with a more ragged appearance than other species. These often occur in smaller patches with a wide range of other cirroform clouds in the sky
• Cirrocumulus castellanus - Taller than they are wide, cirrocumulus castellanus resemble tiny towers sitting high in the sky

https://www.metoffice.gov.uk