Unusual undulating clouds captured in Wyoming

An eyewitness took amazing photos of a rare cloud formation moving along the horizon as if it were huge ocean waves.

The phenomenon known as Kelvin-Helmholtz instability was observed over the Big Horn Mountains from the city of Sheridan (Wyoming).

Rachel Gordon told BBC News that she took these amazing pictures near her parents' house in the US state of Wyoming. She then posted them on a Social network, where they quickly went viral.

The phenomenon of Kelvin-Helmholtz instability occurs when a difference in velocity is formed between two immiscible surfaces "moving" over each other. In this case, the faster air flow moves over the rising air below.

The natural formation is named after scientists Lord Kelvin and Hermann von Helmholtz.