In a rare showing Sunday, Martina Renaud in Cameron spotted "Kelvin-Helmholtz" wave clouds. Kelvin-Helmholtz wave clouds in Cameron, NC - Photo taken by Martina Renaud In a case of KH waves ...

Known as Kelvin-Helmholtz clouds, they form when a faster stream of air moves above rising air below. According to the Met Office website, Kelvin-Helmholtz clouds are "an extremely rare phenomenon".

But few are fortunate enough to see Kelvin-Helmholtz clouds, which look like a pattern of ocean waves in the sky. Kelvin-Helmholtz clouds, also known as fluctus clouds, is a rare phenomenon that's ...