The most astonishing display of atmospheric variability came as giant ocean waves of clouds drifted over the Bighorn Mountains in Wyoming last week.
The incredible scene was captured by photographer Rachel Gordon, who shared them on the Wyoming Through The Lens Facebook group, and is a textbook example of “Kelvin-Helmholtz Instability.”
KHI results from differences in air density between the various layers of the sky—in this case probably from sun heating pockets of air between mountain saddles which rose rapidly into both colder air and strong winds.
“I think everyone should see this beautiful phenomenon,” Gordon wrote in the group.
The Washington Post reported that wave clouds from KHI are not uncommon, but they are fleeting. Perfect examples like the one photographed by Rachel are rare.
Another group member caught a time-lapse video of their movement, which can see them hold their shape as they move across the horizon like tidal waves ready to smash into the coast.