In gallery: Photos of the month (2007)
Related photos: Clouds
The sky turns a neon-colored blue/green as this severe storm rolls in. The lowered cloud base is a turbulent shelf cloud attached to the main updraft of the storm. The remarkable blue or green is often seen at the boundary between updrafts and downdrafts in severe storms and is often thought to signify hail, although the exact cause for the peculiar coloring remains unknown. I personally think it is simply due to the inherent blue-greenish color of a large volume of water and ice when seen under transmitted light. Here, the light is coming from within the cloud. If that is a reasonable explanation, the cloud base and boundaries should not and do not show this color as this is mostly reflected light.
CG lightning was striking at close range all around me at the time I took this photo and I left the scene immediately after.
Photographed on June 3 near Odessa, TX (USA). Nikon FE, Fuji Provia 100F, 14mm lens. Note how the extreme wide-angle lens (and possibly also some earlier storm?) deformed the powerline pole at lower left of the image.