I had an interesting talk with Sean today over lunch. We discussed whether rainfall is a stochastic or deterministic process. At one point, I asked how we should consider a flip of a coin then. Sean brought up the chaoticity theory which says that instead of using a stochastic model, you can have a deterministic one and only change the initial conditions in order to have different outputs. There are some papers on that on Journal of Hydrology.
This is definitely something to check out, though I certainly have to focus on what I am doing.