The following is from guest writer and meteorologist Kim Klockow.

Matt brought a really interesting set of pictures to my attention, and requested an explanation of the clouds. More than happy to do so

As Matt had been hinted to, these clouds are classic gravity wave clouds. This might sound weird to people who focus on gravitational forces with respect to interplanetary forces (my dad in fact just had the same WTF reaction), but in atmospheric fluid dynamics, gravity waves are actually very common.

Gravity waves result from a vertical displacement, and gravity’s attempt to restore the parcel’s position downward. The way to think about a gravity wave coming about is to imagine the first step in severe weather forming — a strong updraft rising into the atmosphere. Given this rising motion, mass around the updraft is displaced — just think of a drop of water hitting the surface of a lake, except in this case, the ripples will propel where the winds blow them, and the presence of wind shear can actually amplify the wave motion.

Significant gravity wave clouds occur with strong force to back them up — in highly unstable atmospheres with some boundary (like a front) present. We may not see them, often, because of the presence of other low-level clouds obscuring the view of that small layer of wave motion (especially here in Indiana, where we’re prone to getting mixed clouds that result from systems already having a long history). I personally see clear wave pattern clouds from the ground much more frequently in the Plains than here.

I had made a pic using a satellite image to point out what’s going on, but this thing won’t let me load my own images, SO here’s a Storm Prediction Center image which will more clearly explain what’s going on.

You can see the amplfying wave pattern ahead of the boundary (front). While storm chasing, this is often a feature we look for to initiate convection ahead of a front — like that SPC case study shows, the wave pattern can lead to severe weather events on its own.

So… when you look in the sky and see patterns to the clouds and you think they look like waves… you’re right. There are a lot of wave types that show up in clouds, all the time. You can probably correctly imagine the ways a lot of the clouds form just by guessing at what’s happening at different layers. The atmosphere is just like an ocean, it’s a fluid subject to whatever forces happen to influence it, only for you… you’re on the bottom looking up.