I agree with you that the weather manipulation thing is fun to think about - and frightening at the same time.
I totally believe that humans have this ability, at least to stir things up, but I don't know how well they can actually control things once they get started - yet; I don't believe that is far behind.
When I was in college 12+ years ago, I took a class in Chaos theory. If anyone is interested in weather, look this up. Weather is the prime example of a chaotic system. "Chaos" isn't really what it sounds like from it's name. There are actual mathematical formulas which predict these systems and the more precise calculations you have for input, the more accurately you can predict. I totally believe that someone could create certain conditions in the atmosphere knowing that a hurricane or tornado or whatever would be the outcome - (look up "starnge attractors"). These sciences move along so quickly; what I learned in college 12+ years ago was introductory material back then.