Environment Planet Earth Strange Wave-Shaped Clouds Roll Across Mount Pisgah By Catie Leary Writer and Photographer Georgia State University Catie Leary writes and curates visual stories about science, animals, the arts, travel, and the natural world. our editorial process Catie Leary Updated June 20, 2019 Wave clouds over Mount Pisgah in Asheville, North Carolina. (Photo: Grant W. Goodge/Wikimedia Commons) Share Twitter Pinterest Email Planet Earth Weather Outdoors Conservation At first glance, you might assume this image is the result of some elaborate Photoshop trick, but trust us, it's 100 percent real! These bizarre, tubular clouds spotted looming over Mount Pisgah in Asheville, North Carolina, were created by a Kelvin-Helmholtz instability, a natural phenomenon that occurs when there's a difference in velocity between two interacting fluids. The clouds are named after Lord Kelvin and Hermann von Helmholtz, who studied the physics behind this beautiful phenomenon. An example almost everyone has seen is when wind blows over water. In the air, it's much cooler. It works like this: First, air is pushed up the steep slopes of the mountain to form clouds in a process known as "orographic lift." Next, swift winds collide with those newly formed clouds, and the resulting Kelvin-Helmholtz instability causes them to curl like giant ocean waves. As EarthSky explains, The clouds are a good indication of instability, meaning if you see these when you fly, it might be a bumpy flight. More proof that fact is often stranger than fiction.