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.
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"First day of summer waving goodbye over Auckland," it said in a Facebook post.
Sightings of the clouds are rare in Auckland and were relatively short-lived last night, only lasting several minutes before fading, the forecaster said.
Niwa shared time-lapse footage of the cloud to its social media channels.
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.