Cryptic clouds in the sky crushed and crashed across Virginia Smith Mountain Lake on Tuesday night, as gigantic breakers in the ocean.
These rare clouds, known as Kelvin-Helmholtz instability waves, were spotted and photographed by Amy Christie Hunter around 8:30 pm
"It was the coolest cloud formation I think I've ever seen!" she wrote on her Facebook page. "It was so amazing."
Hunter's photo has become viral, as shown on local and national broadcasts and websites. Kelvin-Helmholtz instability clouds form variation in air density between adjacent layers and the resulting difference in wind velocities known as shear. These clouds are extremely short-lived and they break in the same way as a wave on the shore – as the bottom layer moves slower than the top layer and the top increases and crashes.
To initiate these wave clouds, you need a disturbance or interference to interfere with the air flow. They usually only last 10 minutes or so before they collapse.
They are most commonly near mountain ranges because of the stratified air above them, but they can form anywhere and display the flowing nature of the atmosphere.
Here are two other textbooks examples of these cloud formations, both from 2015:
from Breckenridge, Colo.
From the Galapagos Islands:
More about Kelvin-Helmholtz wave clouds
Radical Kelvin Helmholtz dares clouds in the Rockies
Pic of the week: Remarkable wave clouds paint the sky over Utah
Pic of the week : Surf up for snow lovers, incomparable Kelvin Helmholtz clouds in Breckenridge
Shark fen in the sky: Awes ome Kelvin-Helmholtz clouds from Galapagos