Chaos theory hurts my head. I read a book about it once and went "muuuuuuuuuuhhhhh!" for days afterwards. Lots of stuff about ratios and "e" and how it crops up in nature a lot - i remember there being something about the factor a river bends being directly equal to it, or as near as makes no difference.
Fractals and water turbulence and, yes, some stuff about weather predictions figured too - in fact what I was saying about the problem with the weather grid system came from that book, now I think about it; there was a section on a weather simulation system giving different results for each run and things.
I might try reading it again sometime and see if I grasp it any better.
[edit]
I'm almost certain it's this one:
http://www.amazon.co.uk/exec/obidos/...464901-4231613
It's at my parents house so I can't tell for sure.