No Photoshop here! Stunning 'breaking waves' clouds spotted over Christchurch

The ocean looked as if it was in the sky when distinctive wave clouds appeared over Christchurch last night.

These koru wave clouds had Christchurch residents in awe last night. Source: Facebook/Christchurch Life

Christchurch's Ashley Harvey photographed a cloud formation, technically known as Kelvin-Helmholtz waves, in the southern sky near Christchurch International Airport about 8pm.

Kelvin-Helmholtz Waves in Palmerston North (Helen Hardy)

Nearly two weeks ago, on February 19, the same formation was spotted near Palmerston North.

1 NEWS weather presenter Dan Corbett said the formations were called Kelvin-Helmholtz Waves, but were commonly dubbed as being like "waves crashing at the beach".

They were caused by strong winds in a stable environment with warmer air just above the clouds.

The layer of strong winds at the upper portion of the cloud moves faster than the layer below and thus allows the cloud to break just like waves breaking at the beach.

The upper layer of cloud is also drier than below which helps evaporate the edges of the cloud quickly.