Meteorologist explains strange cloud formations spotted above Whanganui

The "bobbly shapes" of the mammatus clouds spotted in the sky above Whanganui. Photo/Jocelyn Parker

Those with a keen eye on the sky spotted strange cloud formations above Whanganui on Thursday afternoon.

Metservice meteorologist Lewis Ferris said this type of cloud - mammatus cloud - appeared “pillowy with lots of these bobbly shapes”.

“It tends to be related to a sort of instability in the atmosphere at that cloud layer,” he said.

The colder air is able to sink down within the cloud which makes the cloud take on droopy shapes.

“You most likely see that type of cloud when there’s some sort of weather occurring.”

He said in most cases mammatus clouds meant that there was bad weather and rainy conditions on the way or nearby.

“We don’t get them with every weather system that comes through, so they’re quite unique.”

Whanganui residents also witnessed a trick of the light which made the clouds appear to form a light-filled ‘V’ in the sky.

Ferris said this was caused by an anti-crepuscular ray - which happens when the light comes through a gap in the clouds back towards the sun.

“Sunlight comes through a gap in the clouds behind where the photo is taken, and although it may look as if the sunlight is making a ‘V’ that’s all a perspective thing.

“Those lines are in fact parallel.”

Light above the sky on Thursday evening. Photo / Eva de Jong

Although the dark and lights edges appear to be converging in the sky, the lines are actually perfectly parallel.

“People are seeing so far into the distance that the lines appear to meet.”

Ferris said Metservice had been sent in lots of pictures of the mammatus clouds from people around Whanganui.

Eva de Jong is a reporter for the Whanganui Chronicle covering health stories and general news. She began as a reporter in 2023.