Cloud Spotting for Beginners Part 2: Cirrus

Welcome to part two of our cloud spotting for beginners series! A series where we guide you through the most common clouds in the sky.

Cirrus is one of the ten main cloud types, which are known as the cloud ‘genera’.

It is the most delicate looking of them all, appearing as translucent streaks that resemble watercolour brush strokes across the blue sky or ‘rows and floes of angel hair’.

How are Cirrus clouds formed?

Cirrus are the highest of the ten cloud genera and, unlike the lower, water-droplet clouds like Cumulus, they consist of tiny ice crystals.

As these fall from up at the cruising altitudes of jet aircraft, they can pass through layers of the atmosphere that can differ greatly from each other.

It is the changing nature of the air they fall through that gives these clouds their beautifully expressive appearance.

The celestial locks appear to thicken here or thin out there as the varying temperatures and moisture contents of the air cause the ice crystals to grow or shrink as they fall.

Whether they appear brushed into orderly, straight filaments, or messed up into a wild, chaotic confusion depends on how the winds differ through the crystals’ descent. Eventually, however, the ice crystals of Cirrus clouds dissipate away again upon reaching the warmer, drier air below.

When the flowing filaments of Cirrus gradually thicken and merge to cover the sky, developing perhaps into the continuous layer of ice crystals called Cirrostratus, they are conveying a subtle message about the weather in store.

Spreading like this, they are the first sign of an approaching warm front, heralding a cloud progression that can lead, in a few hours, to the thick rain-bearing layer cloud called Nimbostratus, which brings periods of continuous rain or snow.

Keep your eye out for the rest of our Cloud Spotting series and don’t forget to submit your weather and climate photos to the Standard Chartered Weather Photographer of the Year Competition by 18 June. Submit your photos via the Zealous submission platform to be in with a chance of winning up to £5,000!

Submit your photo to Standard Chartered Weather Photographer of the Year

This post is an excerpt from the RMetS book Weather A-Z. The original author is Gavin Petor-Pinney, Founder of the Cloud Appreciation Society, who wrote a portion of the book on the clouds that capture his imagination. Photo © Geoff Jenkins.