<http://en.wikipedia.org/wiki/Lightening#How_lightnin...

<http://www.tulane.edu/~sanelson/geol204/exceptweath....

I should have put my first remark under Mulder's. would have been a better fit.
the circular shape has nothing to do with circular motion. maybe you're a bit confused because "turbulence" is translated as "ma'arbolet", but turbulence should be "hafra'a" maybe. it is not circular.
and "nidme-li" is not a very good excuse for lack of googling.
it's like sitting on the floor in the middle of the world's greatest library, and just playing with "nidme-li" instead of picking up the book you're sitting on and opening it. isn't it a shame?

again, people choose to argue instead of googling it.
when the air passes a top of a mountain, the turbulence has the vertical cross-cut of a gaussian, on both X and Y axes. IT HAS NOTHING TO DO WITH CIRCULAR MOTION!
this is getting very annoying, with the Negev dust devil popping where it doesn't belong.
what would it take to get people to google stuff instead of just opining on it?

if it's the SAME cross section no matter which direction you cut, you have round symmetry.
mentioned the Gauss part to try and give a feeling of the relation between the shape of the disturbance and the shape of the very peak of the mountain. probably could have thought of a better way to give some intuition.
i guess the best way would still be to google it and look for pictures :)
there is no vortex necessarily

well, since the cloud is formed by the wave and not by wind, the interesting thing about it is that it doesn't move, although it's windy.
there are some other cloud types that do that too.