Some wonderful stuff can be found here. The following however, in homage to my new signature, requires special mention . . .


Met Office website for the Winter 2008 – 9 Forecast

Forecast uncertainties

Seasonal forecasts indicate how slowly-varying large-scale climate influences make particular seasonal conditions more likely than others. Random, unpredictable factors (‘chaos’) also partly determine year-to-year variations, and these will sometimes override large-scale influences. Such uncertainties make a probabilistic format, as used here, advisable for seasonal forecasts.