> Tim Vasquez knows enough to state with confidence that thermal
> bubbles with 20-30 K higher temp
"Bubble" refers to a thermal rising. That's not the concern around a cumulus that penetrates into the stratosphere.
Tim Vasquez has amended his web page since -- someone sent him a reference.
Google penetrative cumulus stratosphere temperature
The stratosphere is relatively much warmer air, and dry; that air mass gets displaced when a cumulus penetrates significantly up into the stratosphere.
It's bubbles going _down_ around the edge of the cloud that are the concern.
"It's what you do know that ain't true that will hurt you."