The clouds Johanna snapped a picture of late yesterday afternoon appear to be Kelvin Helmholtz clouds, also called billows. These clouds resemble breaking ocean waves, with rolling eddies seen at the top of the cloud layer. Kelvin Helmholtz clouds are named after two scientists, Lord Kelvin and Hermann Von Helmholtz, who studied the physics that lead to these wave-like cloud formations. Kelvin Helmholtz clouds form on windy days, when two different layers of air in the atmosphere move at different speeds. The winds in the upper layer of air move at higher speeds and cause cloud tops to roll over like a breaking wave. The atmosphere is split into layers when air densities change with height, for example, during temperature inversions.

 

The presence of Kelvin Helmholtz clouds are good indicators of instability and turbulence for aircraft pilots. However the rolling cloud motions seen in Kelvin Helmholtz clouds are often masked by a large amount of cloud cover. Other times, there are no clouds around to demonstrate the wave pattern.

 

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