These clouds are as mesmerizing as they are ominous, and even more so when viewed in timelapse. Alex Schueth, who posted the video, calls them “crazy wave clouds,” but meteorologists know them better as undulatus asperatus — a newly defined cloud type.

The asperatus clouds form in the same type of conditions as the well-known (and much beloved) mammatus clouds, with slightly different wind characteristics up at the cloud level. This time lapse video illustrates what meteorologists know about air and the atmosphere: it’s like a fluid, and the right kind of wind can make very interesting waves.

In 2009, the Cloud Appreciation Society (yes, you can join!) proposed that the undulatus asperatus be officially added to the list of known clouds. However, the World Meteorological Association maintains the list of recognized cloud types, and is in charge of determining what should be included in the International Cloud Atlas. While the asperatus hasn’t been added yet, we think the society makes a good case. If it is added, it will be the first new cloud type since the cirrus intortus was added in 1951.

The term comes from the Latin word aspero, which means “to make rough.” The Cloud Appreciation Society says that this term was used by Roman poets to describe how the sea looked during a cold, north wind. If you’re loving this video, the Cloud Appreciation Society keeps a gallery of user-submitted photos of the asperatus.

Here’s what undulatus asperatus look like in real time: