Is weather cyclic? I'm a sports amateur, and enjoy playing in Ultimate Frisbee leagues in my hometown. In the last years, I've observed some "weird" weather behavior, and wondered if it was some sort of coincidence, or a pattern.
This year, we have a practice every Tuesday, and 90% of the time, weather is bad on this day (rain, strong winds). However, I have a game every Wednesday, and 100% of the time the weather is good (light winds, no rain). My girlfriend has a practice on Mondays, and 90% of the time the weather is fine. I remember a few years back, we had a game on Wednesdays, and inevitably the weather would be bad, whereas the day before or after had good weather.
So my question is, is weather a week long cycle thing? Or is this just coincidence? I admit the sample for this year isn't very big (~8 weeks), but still, I find it odd that the pattern is repeatable every week. Or can it be related to my current location?
 A: Is it cyclic? - Not necessarily. Depends on the initial conditions and the current state of the system and a little bit on the history of states.
Lorenz was both a meteorologist and mathematician. Having derived a rudimentary nonlinear dynamic model of weather he discovered that the set of equations and the outcome of the equations were highly sensitive to initial conditions. This became known as the butterfly effect . 
By modeling the Lorenz equations in simulation you can see that indeed the outcome is different for very small changes in the initial conditions. While there is no equilibrium point there is a region of attraction where the states tend towards what might appear to be cyclic motion, but not necessarily in a repeatable fashion. And then suddenly the system can take off towards another region of attraction. So like the Lorenz system of equations weather can have short term cyclic patterns, but then suddenly change behavior. Thus there is short term predictability but not long term.
This is the general nature of nonlinear systems. And in general all systems in nature are nonlinear at some level - if you just look close enough.
