What are Asperitas clouds? The rare formations and patterns spotted in Devon and Cornwall skies

Asperitas cloud in Devon, wave, smooth, type, stratus
Asperitas clouds over Exeter, Devon Credit: Sandra (@Day76) via Twitter

Wild-looking clouds with beautiful, wavy patterns have been spotted in the skies above the West Country - but what are they?

Asperitas clouds - which create wavy, smooth, undulating patterns overhead - have been seen in Devon.

What are Asperitas clouds?

The distinctive, but relatively rare cloud formations are named Asperitas after the texture of a rolling ocean's surface.

Due to their sheet-like structure, they are also a type of Stratus cloud, with bases between 4,000ft and 10,000ft high.

They are the newest cloud classification for a long time, having been added to the World Meteorological Organisation's (WMO) books in 2015.

Asperitas don't bring any rainfall themselves but they are associated with thunderstorms Credit: Charlie Powell

How do Asperitas clouds form?

This is still up for some debate, as the unusually characterful cloud bases have been seen after thunderstorms have moved through but also during pretty calm weather.

There is a definite organic flow to the shape and appearance which suggests unstable air - the type where there's a lot of heat and energy in the sky.

There must also be plenty of change of direction in the wind at different heights to make the almost chaotic look to them.

What weather do Asperitas clouds bring?

Asperitas do not bring any rainfall themselves but they are associated with thunderstorms so could be surrounded by or mixed with other rain-bearing clouds.

Pictures show Asperitas clouds in Devon

The skies above Totnes full of Asperitas cloud Credit: Dr. Ben King
Asperitas clouds above Exeter, Devon Credit: Tom Morgan
A huge sheet of Asperitas cloud over Devon Credit: Simon Wood
Chillington, Devon with Asperitas cloud as far as the eye can see Credit: Julia Kelland
Asperitas clouds overhead in Bude Credit: Kristina Elderfield
Looking up from Truro to a sea of Asperitas cloud Credit: Marc Searle