With regards to 'How do they draw these things up anyway, do you know?'

No, I have no idea. But as I was cooking dinner tonight I had an epiphany. Due to the rain of which we've already discussed in the hornet thread, we had to move our fire to the protected 'porch area'. (A few square feet with a roof.) As I was cooking, I couldn't help but notice how the smoke followed me. It was spot on. I move, smoke moves. I move back, smoke moves back. My movements were creating 'steering ridges', lows or highs or whatever. It was a micro environment that clearly demonstrated how air follows minor fluctuations in local pressure.