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A spectacular cloud formation delighted those staring into the blue skies in Central Otago yesterday afternoon.
A photo shared by Niwa on social media shows the Kelvin-Helmholtz wave clouds that formed over Lauder, in Central Otago.
"Like Mother Nature's signature in the sky," Niwa described the formations on Twitter.
"These clouds, which resemble rolling ocean waves, were spotted over Central Otago on Sunday," the tweet added.
Kelvin–Helmholtz cloud formations, named after 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.