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Uncategorized Sunday, December 18th 2011 at 12:00 pm

Bizarre Kelvin-Helmholtz Waves Appear Over Alabama

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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.

The example of a strong wind blowing over water is, I think, particularly illustrative. In this case, it seems that cooler, denser air close to the ground is being pushed by warmer air above it. At least, that’s what I think is happening.

Heres what Redditor and meteorologist zensunnioracle had to say:

Meteorologist here. These are indeed Kelvin-Helmholtz waves. What is happening is that the nocturnal near-surface layers (lowest 50-100m) of the atmosphere are much more stable than the layers above it in the mornings. Until the ground heats up due to daytime heating, the surface layers stay more stable than the air over it. Kelvin-Helmholtz waves occur when the wind shear between the layers destabilizes the topmost portion of that stable layer, and entrains the air into the unstable layer. What you see is stable air being lifted, cooled, and condensed so that this process becomes visible, though this commonly happens many places without being visible.

As spectacular as these waves are here on Earth, the same forces create similar patters on the gas giant planets like Saturn and Jupiter. While those are some truly enormous waves, these pictures from alison_bee should show that the Earthbound variety aren’t to be sneezed at either.

Someone also shot a video of the line of wavy clouds.

(Reddit via TYWKIWDBI)

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  • https://twitter.com/#!/haversam [A]

    Creepy stuff..

  • Anonymous

    Dwarfs the imagination! Much like the painting of the Great Tsunami in Japan.

  • Tom D

    The meteorologist is substantially correct about the forces which usually form Kelvin-Helmholtz instabilities, but this particular instance was just a tiny bit different. I was in Birmingham and watched this develop. I pulled over to the side of the interstate to watch, as a matter of fact. Here’s what happened:

    Red Mountain (the ridge on which you see he K-H waves develop) had been cloaked in heavy fog all morning. The cold front we had come through about noon, however, sent cold, laminar wind flowing along and above the ridge. This entrained air and created low pressure above the fog layer, which lifted the fog and formed the waves as you see them.

    So yes, there was highly stable air near the ground. But there was no condensation as uplift occurred, since the water was already condensed in the form of fog. In fact, you could see the fog being lifted off the mountain as the horizontal vortices formed. It was fascinating.

  • http://pulse.yahoo.com/_QPO7ZTNVCETKHPFKPR7DWCSY2Q Anthony

    Okay, I’m waiting for someone to claim this proves that God is angry at Alabama.

  • Max Eddy

    Hey, thanks for the info!

  • Bink Binkerson

    It’s the Hand of Tebow.

  • Lookup HAARP

    I believe this is the HAARP project! (Lookup HAARP) 

  • Mdbrence

    Very cool.

  • http://twitter.com/monkeyfufu monkeyfufu

    We can expect more devastating land tsunamis like this as global warming gets worse. When will the repukes open their eyes and see what they are doing to our environment? How many more people need to die because of your short-sighted greed?   

  • ShellMc

    Roll Tide?

  • Tatianyc

    Looks like dinosaurs are back ~~~~~ “Jurassic Park 4?”