Tornado - Rainbow Optical Illusion?

This is a fascinating image below. When I first saw it I was impressed by what I thought was a good photoshop creation. What do you think is the truth of this image?

Credit: Eric Nguyen (Oklahoma U.), www.mesoscale.ws

As it turns out this is an actual photograph taken by a storm chaser. Sun, rainbow, tornado and hail all colliding in this rarely seen combination. I found this on Astronomy Picture of the Day. They had this to say about this picture.

Explanation: The scene might have been considered serene if it weren't for the tornado. Last June in Kansas, storm chaser Eric Nguyen photographed this budding twister in a different light -- the light of a rainbow. Pictured above, a white tornado cloud descends from a dark storm cloud. The Sun, peeking through a clear patch of sky to the left, illuminates some buildings in the foreground. Sunlight reflects off raindrops to form a rainbow. By coincidence, the tornado appears to end right over the rainbow. Streaks in the image are hail being swept about by the high swirling winds. Over 1,000 tornadoes, the most violent type of storm known, occur on Earth every year, many in tornado alley. If you see a tornado while driving, do not try to outrun it -- park your car safely, go to a storm cellar, or crouch under steps in a basement.