Space filler in the clouds

In the absence of anything else to report - guests all gone, alas, all quiet - I thought I'd post this poor photo of clouds taken a couple of weeks ago. Wish I'd had a real camera with me. Its a phenomena I'd heard of and never seen before; clouds cast shadows onto other clouds, all moving at different rates, and the shadows cast onto the clouds look like moving cities in the sky.
The medievialists reported this from time to time, always some sort of portent. Cant remember what it signifies.