Kelvin-Helmholtz breaking wave cloud over Laramie, Wyo. (NOAA/Brooks Martner)

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Though it looks like someone painted the sky with breaking ocean waves in the collection of photos above, there’s a very good atmospheric explanation for what is really happening.

The rolling, wave-like cloud formations are called Kelvin-Helmoltz clouds. Sometimes they are also called billows. They are named for scientists Lord Kelvin and Hermann von Helmholtz, who discovered the process by which they form.

Severe Weather Expert Dr. Greg Forbes of The Weather Channel says, “They are the atmospheric equivalent of those great breaking waves that you sometimes see on the ocean.”

These breaking atmospheric waves occur in an environment with a large amount of vertical wind shear and stable air. Wind shear is a change in the speed and direction of winds as you go higher in the atmosphere.

In this case, winds at the top of the cloud layer are moving faster than the base of that same layer. This causes the top to crash downwards in a curling manner after it hits the stable layer above.

The rolling motion created by this type of wind shear also causes turbulence for aircraft.

However, the rolling clouds motions are often masked by a large amount of cloud cover. Other times, there are no clouds around to illustrate the wave pattern.

from:    http://www.wunderground.com/news/kelvin-helmholtz-billow-wave-clouds-20130815