May 27 - Rainbow with no Rain?

Iridescent Clouds over RivertonAn observer called the Riverton Weather Service office to inquire about vividly colored clouds she noticed over central Wyoming on May 27th. Upon further examination, meteorologists at the Weather Service have confirmed that these clouds are "Iridescent Clouds."  The colors in Iridescent Clouds are formed in a similar manner to the colors in rainbows. Their formation is done by light bending (diffracting) through uniformly sized water droplets in thin mid to high level clouds. Different colors are related to the varied difference in water droplet distance from the sun, and how much the light has to bend around those droplets. As light diffracts more around these water droplets, different colors are displayed.

The observer reported rich reds, whites, and blues in the clouds she noticed in the early afternoon hours. As the clouds began to dissipate, their color lessened. These iridescent clouds re-appeared throughout the afternoon, allowing some photographs to be taken by meteorologists at NWS Riverton.

 Additional Images of Iridescent Clouds from 5/27/2007

Iridescence Clouds over Riverton, WY Iridescence Clouds over Riverton, WY
Iridescence Clouds over Riverton, WY


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