Unusual 'holepunch cloud' captured over north east Scotland
The unusual cloud formation was spotted over Fochabers village in Moray
- Published
An unusual type of circular cloud formation has been spotted over parts of north east Scotland.
Weather enthusiasts captured images of the fallstreak hole, also known as a hole-punch cloud, over areas including Fochabers, Auchleven, Turriff and Kingston.
The unique and seemingly unworldly marvel occurs when an almost circular or spherical hole appears in an otherwise uniform cloud layer.
It is all thanks to water droplets that are colder than freezing yet remain liquid.
These supercooled droplets are in mid to high level cloud layers such as cirrocumulus or altocumulus.
This shot was taken at Auchleven, Aberdeenshire
How do fallstreak holes form?
The droplets remain liquid as the air is super clean at that altitude, without any particles such as dust or pollution.
It means the water droplet does not have a reason to freeze as it does not have a nucleus to grab a hold of and freeze around.
However, a change occurs when an aircraft flies through the cloud layer.
Air around the aircraft wing and body can expand and cool creating ice crystals.
The cloud was also spotted over the village of Kingston in Moray
Those ice crystals then become the nucleus for the water droplet, giving it a reason to freeze.
The supercooled water droplets then start to freeze in a chain reaction that spreads out from the centre, with water droplets next to each other freezing in an outward motion.
As the water droplets freeze they fall from the sky, leaving a circular or spherical hole in the cloud.
You can often see some wispy cloud in the middle of the hole and that is the ice crystals falling from the cloud.
A bright shot of the cloud's ripple effect taken in Turriff, Aberdeenshire