'Wave Clouds' Over Birmingham, Alabama Explained (VIDEO)
Birmingham, Alabama got hit by a massive tsunami last week ... a tsunami of clouds.
The surreal waves graced the skies Friday afternoon, giving residents a treat few had seen before, according to ABC 33/40. The event was rare enough to spark a flurry of YouTube videos, like the one below.
But what's happening in the sky is perhaps not as rare as many thought. The effect even has a scientific name, the Kelvin–Helmholtz instability. It generally occurs at the cloud level in areas where winds can build up significant speed.
LiveScience explains the occurrence:
Whether seen in the sky or in the ocean, this type of turbulence always forms when a fast-moving layer of fluid slides on top of a slower, thicker layer, dragging its surface.
The same thing happens when waves form in the ocean, as thicker fluids are pulled by less-dense, fast-moving air. In this instance, however, it's simply a case of less-dense air (shearing winds) pulling on denser air.
This example was perhaps one of the most pronounced in recent history and it spread particularly quickly online largely because it was observed in an area of dense population.
ABC compiled some great images of the clouds, which you can see here.
Want to see something else incredible in the air? Check out this video, entitled "Murmuration," which depicts a phenomenon that's a bit more lively.
WATCH:
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The Huffington Post Dean Praetorius
First Posted: 12/19/11 07:06 PM ET Updated: 12/19/11 08:07 PM ET