boon's log 1306.04: Billow Clouds

We were fortunate enough to be able to observe this rare shape of clouds, known as billow clouds, as a result of what is known as shearing instability (or the Kelvin-Helmholtz instability). These clouds, looked like waves on top of the ocean, formed above the Sierra Mountains.


The Kelvin-Helmholtz waves

Google it and you may find some explanations like this...
"Billow clouds are created in the upward branch of each of the eddies if the air within this branch has a high enough relative humidity that, upon lifting, the air parcel reaches saturation. Individual billow clouds generally have life times of a few minutes. The presence of billow clouds provides a visible signal to aviation interests of potentially dangerous turbulence."

boon out...