View at EarthSky Community Photos. | Matty Hammersley in the UK wrote: “Taken by my wife Ems whilst i was driving south on M5, south of Birmingham/Black Country towards Worcestershire area.” The image is from around sunset, on March 28, 2022. The clouds are known as Kelvin-Helmholtz clouds. Thank you, Matty!
Clouds that look like waves are rare and beautiful. These clouds – known as Kelvin-Helmholtz clouds, billow clouds, or shear-gravity clouds – might have been the inspiration for Van Gogh’s painting Starry Night. The next time you spot one of these remarkable wave clouds, capture a photograph and submit it to us!
Kelvin-Helmholtz clouds are named for Lord Kelvin and Hermann von Helmholtz, who studied the physics of the instability that leads to this type of cloud formation. A Kelvin-Helmholtz instability forms where there’s a velocity difference across the interface between two fluids: for example, wind blowing over water.
How to see Kelvin-Helmholtz clouds
When might you get to see these beautiful clouds? Your odds are better on windy days, when there’s a difference in densities of the air – for example, during a temperature inversion – when warm air flows over cooler air. You’re also more likely to see these clouds near sunrise or sunset, another time when the bottom of the clouds are cooler and the air above is warmer. The clouds take on this wave shape when the air above is moving more quickly than the air below, pushing over the tops of the clouds and creating the rolling wave appearance. As you might have guessed, Kelvin-Helmholtz clouds are a sign that aircraft in the area will be experiencing turbulence.
“Wave clouds” from the EarthSky community
View at EarthSky Community Photos. | Early on the morning of May 23, 2021, Angus Weller spotted these Kelvin-Helmholtz clouds over the Coastal Mountain Range just north of Vancouver, British Columbia. Angus said: “It’s only the 2nd time I’ve seen this cloud formation.” Thank you, Angus!View at EarthSky Community Photos. | Michelle Berger in Sandpoint, Idaho, captured this photo of Kelvin-Helmholtz clouds on December 27, 2020. She wrote: “We were driving home one evening in December, 2 days after Christmas, and saw this beautiful image in the sky east of our way home.” Thank you, Michelle!View at EarthSky Community Photos. | Suzanne Kelley of Littleton, Colorado, caught these Kelvin-Helmholtz clouds – clouds that look like ocean waves – at sunset over the Rocky Mountains on New Year’s Eve, December 31, 2019. Thank you, Suzanne!Surf in the sky. Image via Yoav Naccache. Thank you, Yoav!Kelvin-Helmholtz clouds seen in Tupper Lake, New York, in the Adirondack Mountains. Photo via Paul Chartier. Thank you, Paul!View larger. |EarthSky Facebook friend Risa Bender caught these Kelvin-Helmholtz clouds from Dallas, Texas. Thank you, Risa!Cindy Gurmann caught these Kelvin-Helmholtz clouds near New York, New York, in March 2015. Thank you, Cindy!Helio de Carvalho Vital caught these Kelvin-Helmholtz clouds over Rio de Janeiro, Brazil. Thank you, Helio!View larger. | Helio de Carvalho Vital also submitted this photo to EarthSky. It’s a Kelvin-Helmholtz effect in virga, or rain that falls but doesn’t reach the ground. He caught it in Rio de Janeiro, Brazil, on May 15, 2015. Thanks again, Helio!Earth isn’t the only planet with Kelvin-Helmholtz clouds. Here they are on Saturn; Jupiter has them, too. Image via Wikimedia Commons.
Bottom line: Clouds that look like waves across the sky are known as Kelvin-Helmholtz clouds. These clouds form from winds moving at two different speeds.
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