"Billow Clouds/Kelvin-Helmholst Waves"

The common name for these clouds which resemble waves of the ocean breaking on the shore is "Billow Clouds". They result from a shearing instability formally called dynamic instability (or Kelvin-Helmholtz instability, after Lord Kelvin and H. von Helmholtz). Such shearing instability also causes the flapping of a flag.

In the case of this picture, entitled "Waves of Ascension", there is a vertical wind shear because winds near the summit of Mt. Shasta are ostensibly blowing at slower speeds than the winds several hundred to a couple of thousand feet higher up. Waves generated in a vertically sheared layer of air, also form perpendicular to the wind shear, thus waves, or ripples can still form in a stable layer of air if vertical wind shear is sufficiently strong.

This example in the afore said photograph is extremely rare to be so perfectly formed and is one of the best examples ever seen, one that the majority of people will never see in their lifetimes...This particular picture has been viewed on the Pennsylvania public broadcasting television station and was featured in an issue of "Weatherwise Magazine."

This is an excerpt from an article written by Lee Grenci, a meteorologist, describing in full the dynamics of this system. This photograph has gone all over the world, and is becoming well known and collectible.




Kelvin-Helmholst in the news

Amazing Waves Discovered in Deep-Ocean Trench


Billow Clouds/Mt. Shasta
Billow Clouds/Mt. Shasta
Billow Clouds/Kelvin-Helmoltz/mt. shasta
Billow Clouds/Mt. Shasta


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