On Friday a series of strange clouds rolled across the Birmingham sky. Photos of the wave-like clouds spread across the internet as people wondered, what in the heck are those?
According to Life’s Little Mysteries, the clouds are pristine examples of “Kelvin-Helmholtz waves.”
Kelvin-Helmholtz waves form when a fast moving layer of fluid slides on top of a slower layer and drags its surface.
In this case, quicker clouds at higher altitudes are pulling at larger, slower clouds closer to the ground.
Chris Walcek , a meteorologist at the Atmospheric Sciences Research Center at the State University of New York, Albany, said:
“There is probably a cold layer of air near the ground where the wind speed is probably low. That is why there is a cloud or fog in that layer. Over this cloudy, cold, slow-moving layer is probably a warmer and faster-moving layer of air.”
Walcek explains that the difference in wind speed between two layers of clouds is usually small, which means that the top layer normally just slides across the bottom layer of clouds. If the difference in speed is too great, the clouds will mix in random turbulence. It takes the perfect combination to create these wave-like clouds.
“What [these pictures] show is air between these two atmospheric layers that is just very close to that threshold for turbulence, and mixing to mix the two layers together.”
Here’s a video of the tsunami clouds over Birmingham.
Have you ever seen Kelvin-Helmholtz waves in action?