#WxGeekSpeak: Kelvin-Helmholtz clouds

Every week, the blog introduces you to a technical term from the American Meteorology Society’s “Glossary of Meteorology”. Welcome to #WxGeekSpeak!

One of our loyal viewers noticed these wavy clouds earlier in the week. What are the called & how do they form? Click the video above to go inside the science of Kelvin-Helmholtz clouds.

Full definition of Kelvin-Helmholtz clouds: An instability of the basic flow of an incompressible inviscid fluid in two parallel infinite streams of different velocities and densities.

If the overlying fluid has velocity U2 and density ρ2, and the underlying fluid has velocity U1 and density ρ1, disturbances of the form eikx (where k is the wavenumber) are unstable if

ams2001glos-Ke2

where g is the acceleration of gravity. Thus, the flow is always unstable to short waves (high wavenumber) if U1U2.

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