Unfortunately, I've never seen a real tornado. But that doesn't stop me from making a cool picture of one (I've never seen unicorns, dragons, and dinosaurs, either, but I still have pictures of them). I found this old, abandoned home in Arizona many years ago, and I used it as a foreground for an approaching storm. I started with two shots of storm clouds that I blended together. Then I created the funnel with the lasso tool and feathered the edge 20 pixels. The horizontal striations inside the tornado that suggested a spinning motion was the hardest for me to figure out. In the end, I took the storm clouds and using Edit > transform > scale, I squeezed them down so the light and dark values of the clouds became streaks. I added the debris cloud at the base of the tornado with the clone tool, and the lightning -- which often accompanies tornadoes-- was added by using the blend mode 'lighten'.