Flying over the Alps, coming back home in the evening, I noticed the clouds below moved by strong winds in many waves, following the orography of the mountains. I found interesting this effect, especially if compared with the clear sky over them. I choose to use black and white because it stress the attention to the wave shapes.

Update: this image has been one of the 15  most popular pictures in the weekly themes by VFXY for the July 24, 2009 week, when the theme was “Null or Empty”