If there was any doubt Mt Maunganui is a surfer's paradise, one only had to check out the gnarly clouds hanging above it yesterday.

Local surfer Ben Haarmann was struck by the clouds' surf-like appearance and took a snap of it.

"Unfortunately, the surf wasn't very good that day but it was really cool to see the clouds, it was quite neat," Haarman said.

"I shared it among my friends and they sent it everywhere as well; someone thought it was photo-shopped but I said, nah, if it was photo-shopped it would have had a blue sky."


Philip Duncan of Weatherwatch.co.nz, which has also shared the pictures, said the rare and stunning clouds were known as Kelvin-Kelmoltz clouds.

"The rolling, wave-like cloud formations are also known as billows," he said.

"The clouds are named after scientists Lord Kelvin and Hermann von Helmholtz, who discovered the process by which they form."

Dr Greg Forbes of The Weather Channel in the US described them as the
"atmospheric equivalent of those great breaking waves that you sometimes see on the ocean".

The breaking atmospheric waves occurred in an environment with a large amount of vertical wind shear and stable air.

Wind shear was a change in the speed and direction of winds as you go higher in the atmosphere.

In this case, winds at the top of the cloud layer were moving faster than the base of that same layer, causing the top to crash downwards in a curling manner after it hits the stable layer above.

The rolling motion created by this type of wind shear also caused turbulence for aircraft.

However, the rolling clouds motions were often masked by a large amount of cloud cover.

At other times, there were no clouds around to illustrate the wave pattern.