Feather Fall Streak Over Snowflake, Arizona

August 18, 2008


Provided by: Jerry Lowell
Summary Author and Editor: Jerry Lowell, Jim Foster, Stu Witmer

The photo above looks more like a feather than a cloud. It's actually an impressive fall-streak cloud. It was taken March 1, 2008, about noon, above Snowflake, Arizona. While standing in my back yard, our neighbor’s son who was helping us paint just looked up in the sky and said “Look, there’s a feather.” I ran in the house, grabbed my camera and took this photo.

Fall-streaks result when the cloud droplets, ice crystals or supercooled water droplets composing a cloud are agitated in some way and suddenly fall out. Usually, they form when ice crystals from a higher cloud level fall through a lower, thinner cloud layer, as seems to be the case here. Note the clear area of blue sky surrounding the "feather." Supercooled water droplets in this lower layer freeze as the crystals pass through, and this freezing action acts to release heat (latent heat of fusion), which warms the air and causes the surrounding cloud droplets to evaporate. Thus, this precipitation readily rarely reaches the surface.