Incredible rare cloud formation spotted over Auckland skies

Clouds resembling waves could be seen rippling across the Auckland sky last night. Photo / WeatherWatch

A rare and short-lived cloud formation was spotted over Auckland as the sun was setting yesterday evening.

Incredible photos in Auckland show wave-like clouds rippling across the sky.

WeatherWatch said the official name for the clouds is Kelvin-Helmholtz.

The forecaster shared a photo of the formation on social media.

"First day of summer waving goodbye over Auckland," it said in a Facebook post.

Don't see them too often over #Auckland either! :) #KelvinHelmholtz Clouds https://t.co/lxneIrMkQS

— WeatherWatch.co.nz (@WeatherWatchNZ) December 1, 2020

Sightings of the clouds are rare in Auckland and were relatively short-lived last night, only lasting several minutes before fading, the forecaster said.

First day of summer waving goodbye over Auckland (Kelvin-Helmholtz clouds is their official name). Rare to see them in...

Posted by WeatherWatch.co.nz on Monday, November 30, 2020

Niwa shared time-lapse footage of the cloud to its social media channels.

Stunning Kelvin–Helmholtz wave clouds spotted dancing across Auckland's sky at sunset 😍 pic.twitter.com/0RbUZT08LG

— NIWA Weather (@NiwaWeather) December 1, 2020

Kelvin–Helmholtz cloud formations, named after Lord Kelvin and Hermann von Helmholtz, are extremely rare.

They occur when there is a strong vertical shear between two air streams, which leads to winds blowing faster at the upper level than at the lower levels.

That difference in speed causes the wave-like formations in the clouds.