Late on the afternoon of August 17, 2004, a massive thunderhead formed over Southern California's Anza-Borrego Desert―not far to the southeast of Borrego Springs.  As the cloud was struck by reddened light from the setting sun on the opposite side of the sky, it burst into view like an atomic blast.  The cloud was so immense that it was noticed from more than 70 miles away, and required five wide-angle images stitched together to capture it all.