We went to the far west a week or so ago. Friends were visiting, and we went to the Aquinnah Shop for breakfast. The Aquinnah Shop perches atop the Gay Head Cliffs, and is worth the trip to the far end of Martha’s Vineyard.
It was a weathery sort of day, with clouds, wind, and showers.
Windslanted showers, over the Elizabeth Islands. We are looking north from Aquinnah.
The day was atmospheric.
As we were leaving, we were treated to an ephemeral phenomenon.
You don’t see these very often.
In this case, there was a strong wind blowing over the top of the stratus layer.
Making waves in the sky.
They’re called Kelvin-Helmholz instability waves.
What a sight to see!
Postscript, August 11, 2017.
Coming out of Quansoo, we looked up, and there in the northwestern sky was another little patch of K-H waves.
thetompostpile 
excellent clouds…they look like cumulus to me….
The day was very stratusy…Here are some links to K-H cloud info.
The first link has a lot of photos.
http://www.amusingplanet.com/2013/07/kelvin-helmholtz-clouds.html
http://www.brockmann-consult.de/CloudStructures/kelvin-helmholtz-instability-description.htm
https://en.wikipedia.org/wiki/Kelvin–Helmholtz_instability
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