While driving through Birmingham, Alabama, Redditor alison_bee couldn’t help but notice the bizarre, repetitive wave shapes appearing in the clouds near the horizon. While these strange cloud formations look otherworldly, they’re an example of what’s called Kelvin-Helmholtz instability — which is a pretty awesome name for a spectacular phenomenon.

Here’s how Wikipedia describes what you’re seeing:

[…] when velocity shear is present within a continuous fluid, or when there is sufficient velocity difference across the interface between two fluids. One example is wind blowing over a water surface, where the wind causes the relative motion between the stratified layers (i.e., water and air). The instability will manifest itself in the form of waves being generated on the water surface.

via Geekosystem

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