Departing Storm Clouds

September 24, 2010

Photographer: Tommy Hornbeck
Summary Author: Tommy Hornbeck; Jim Foster

It's been bone dry in western Missouri for weeks, so a little rain was well appreciated. However, we didn't bargain for a 24 hour rain storm --  almost seven inches (175 mm) fell during this deluge. The photo above, taken near sunset on September 1, shows the backside of a juicy storm cloud departing toward the east. The interesting texture of this convective cloud can be readily observed since it's being illuminated by the setting Sun -- the weather had just cleared off in the west. Since most thunderstorms in the mid-latitudes advance from the direction of the Sun, which is obscured as the storm grows nearer, it's difficult to notice structural details in the approaching but shadowed clouds. Note the pendulous nature of the clouds lower in the sky. This may be related to mammatus development.

At sunset and sunrise, longer wavelength, red-orange colors result from the increased path length of sunlight when the Sun lies close to the horizon. In essence, the shorter wavelength colors (blue and violets) are more effectively scattered by air molecules from our view.

Photo details: Camera Maker: NIKON CORPORATION; Camera Model: NIKON D80; Focal Length: 25.0mm (35mm equivalent: 37mm); Aperture: f/4.2; Exposure Time: 0.017 s (1/60); ISO equiv: 100; Exposure Bias: none; Metering Mode: Matrix; Exposure: program (Auto); White Balance: Auto; Flash Fired: No; Color Space: sRGB. Photo under exposed around three stops to heighten saturation.