Tornado - Rainbow Optical Illusion Image?

This is a fascinating image. 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?
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.