"Graham P Davis" wrote in message
...
Looks like a not uncommon occurrence where cumulus has convected into a
moist and more stable layer, then spread out into a skirt of Sc, but have
enough energy to then poke through that layer. Then it looks as though it
may have hit another layer and begun to spread out into the mushroom cap.

For another photo of this, see
http://www.wolkenatlas.de/wolken/gvert04.htm - the fifth picture on this
page, Cu congestus.

Does look a similar idea, thanks for the explanation!

If you wander through the other pictures in this section - first drop-down
panel "Weitere Galerien" - you might find other examples, or not. Anyway,
there are some great pictures there.

Yeah, nice pictures on there, will have to bookmark that one!

James