On Friday March 11, 2016, just before sunset a thin band of Kelvin-Helmholtz clouds developed above a cumulonimbus anvil.
They then became iridescent for three minutes before dispersing over Mutare, Zimbabwe.
These clouds, sometimes called “billow clouds,” are produced by the Kelvin-Helmholtz instability when horizontal layers of air brush by one another at different velocities.
It is widely believed that these waves in the sky inspired the swirls in van Gogh’s masterpiece The Starry Night.
The delicate pastel colors of the waves come from irridescence – the diffraction of sunlight by tiny water droplets in the clouds.
Awesome Van Gogh clouds in the sky of Africa.