There's always ONE in the crowd! "WHEEEEEE" he says, while the rest of the Choir looks on...
I have a series of this cloud approaching Mount Shasta (foothills on the lower right), and then blending in with the Lenticular cloud which was already there. Water vapor. Uh-huh.
The phrase "Clouds like flames burned white across the sky..." filled my mind as these glowed in the evening sunlight.