Subject: What explanation is there for a light source moving behind a thunderhead?

Near sunset (8:15 pm local time in late June), three of us witnessed a 
thunderhead, probably 5 miles distant. If the cloud was at the 12:00 
position, the sun was at 11:00.  At the top of the cloud was what seemed 
to be light refracted from the sun.  But the apparent light source 
suddenly moved, looking as if it turned about 120 degrees 
counterclockwise, and in a horizontal plane.  Then it stopped.  After 
several seconds, it again turned and stopped.  For several minutes we 
watched this, and it continued with the same type of pattern, but not with 
a fixed pattern.  However, it alway turned with a period of probably 5 
seconds, and always stopped suddenly after turning.  After sunset, the 
light was no longer visible.  However, it is very hard to understand how 
this could have been sunlight.  I am baffled.

Re: What explanation is there for a light source moving behind a thunderhead?

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