It’s been 63 years since we’ve classified a new kind of cloud. You’d think that after hundreds of years of looking up at the sky and documenting the dollops of gaseous whipped cream we see, there couldn’t be many more clouds nature could throw at us. But we’ve found a serious contender in those intervening years, and it rolls like an ocean in the sky.

Since 2009, Gavin Pretor-Pinney — who runs the delightfully named Cloud Appreciation Society — has been trying to get these spectacular formations officially classified by the World Meteorological Organisation. He calls them Undulatus asperatus clouds, meaning “roughened or agitated waves.” The WMO hasn’t officially recognized the clouds yet, but more and more evidence of them has been rolling in, especially in the last 10 years with the advent of affordable cameras and social media.

Student and photographer Alex Schueth is providing the evidence for Undulatus asperatus seen above. A self-proclaimed storm-chaser, Schueth captured the incredible time-lapse below, showing asperatus clouds undulating over Lincoln, Nebraska two months ago. Check out the full video below:

Besides these clouds being an example of a potential new kind of cloud, the hypnotizing way they move shows a curious bit of physics — air moves and acts like a fluid.

Think of it like two oceans stacked on top of each other. Underneath the asperatus clouds sits air of a different temperature and pressure. These differences separate it from the ocean of air above — the clouds. The layer where these two air oceans intersect is turbulent, and produces wave patterns we would expect if two bodies of water flowed past each other.

For example, clouds moving over islands can produce the same kinds of patterns that we see in fluids!

Whether or not Undulatus asperatus will become a new kind of cloud, the physics behind them is fascinating and gorgeous. Hard to say what shapes I see in it though. An ice cream cone? A kitten? No, definitely the underside of a wave.

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IMAGE: Approaching Asperatus Cloud by B.J. Bumgarner

HT: PetaPixel