Distant Clouds and Crepuscular Rays

October 27, 2006


Provided by: Elaine Martin, UCAR Satellite Imagery
Summary authors & editors: Tim Martin

On the evening of September 16, 2006, I was driving with my family across north central Illinois and was privileged to see a phenomenal display of crepuscular rays coming from an apparently cloudless sky. We were driving westward on I-80. The display was visible for over 45 minutes, well after local sunset. The top image was photographed near the “X” on the image below.

Even though we were still under clear skies after reaching our destination, near Tiskilwa, Illinois, I assumed that the display was caused by sunlight passing between distant cumulonimbus clouds. Upon arrival at our hotel, I quickly logged on to the web and downloaded the current GOES Infra-red satellite image to determine the cause of the spectacular sunset. Well over the horizon from our location, the -65 degree C (- 85 F) cloud tops, stretching from Kansas to Minnesota, indicate the significant height of these towering clouds. I was a bit surprised to see that the storms that were responsible for this event were 400-450 miles (640-720 km) to the west! These storms produced severe weather in Iowa and Nebraska. Note that the spacing of the storms also contributed to this inspiring display of crepuscular rays.

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