Mongo, thanks sharing your analysis of the image.
Folks, here is the situation in which I shot these images:
All images were shot from the emergency stairs on the 6th floor, my usual shooting position for the Tokyo cityscape panos. At first, I found the clouds in #1 attractive, decided to make pano of them, shot two frames and went back to my room. Some 20 minutes of minutes later, I found the color of the sky had changed completely, looked out of the window and found that the same clouds shining in orange backlit by the sun that had been covered with the clouds in the pano. I dashed up the emergency stairs again and shot #2.