Ok the mini debate in the Nosey thread got me thinking about all my pet theories. I have always sensed or believed that there are significant re-occuring weather cycles. I have a theory which has developed more based on other planets weather systems than ours. I have looked at beautiful pictures and movies of Jupiter and wondered how the horizontal weather bands or wind bands remain so distinct or separate. My conclusion which will probably not come as some great surprise is that Jupiter is a gas giant and we only see the outer most extent of the visible atmosphere. If as some might suggest there is a solid core of Jupiter, its irrelevant in many ways because the weather or turbulence we see is far removed from and surface interaction. Hence my theory is that the atmospheric systems are able to reach and semi-permanent equilibrium state according to its speed of rotation which maintains a seemingly static and perhaps predicible weather system. If we take this scenario to our planet we only have to look at the quasi-biennial oscillation to realise that in the upper atmosphere of Earth there exists a fairly predictable and regular wind pattern. This exist in part I believe to is isolation from turbulence from the earths surface. As we move further down towards the surface regular wave patterns or cycles become increasingly obscured by the influence of surface turbulence. However, this influence is in varing degrees. If you look at the upper tropospheric patterns at say 500-300hpa (5500-9200m aprox) in the southern hemisphere around the poles they exhibit a certain amount of regularity. It is these patterns that Frog uses with some success and therefore they can be used for longer term forecasting. Example of southern hemisphere circulation pattern at 500hpa. However, these same upper level patterns are less regular and therefore useful in the northern hemisphere. This I think is fairly uniformly accepted as being due to continental disruption. Example of northern hemisphere 500hpa circulation: Also the fact that the southern hemisphere has a land mass near as damn it central over the south pole and surrounded by sea at mid-latitudes is a good set up for setting up a fairly regular and uniform flow (e.g. at the surface the roaring forties). So in the southern hemisphere we are blessed in a way by having seemingly more regular weather patterns than the north, but alas the price we pay is very few observations. I am sure all of you that have been to the central or east coast states of America will love how the weather stations will tell you its going to rain, snow or be sunny the next day and 9/10 times it does. This is because the weather you are about to get has been observed and measured imediately upstream in the next state the day before. So in a way, apart from the uncertainty in developing systems, its hard to get it too wrong. (very simplistic view of course) So where am I going with this? Good question and I am not sure, but I hope discussion will ensue. I believe that there are many different significant wave patterns that are all out of sync most of time, but on occasions many of them become phased locked to give great or poor snow seasons or perhaps on the shorter scale a week or two of good snow producing storms. If we start listing them, we might start with Long wave troughs ignoring the fact why they are there for now but just consider them an existing buckling of the circumpolar flow. lets add short wave troughs which ride around the roller coaster of the long wave troughs which can enhance them or even destroy them or at least modify them. Throw in things like oscillations in the sea surface temperatures that travel around the circumpolar current. Tropical sea temperatures in particular the current El Nino state. The Madden Jullian oscillation. The annual movement of the intertropical convergence zone and subsets of this such as the Indian Monsoon, its onset and strength. All of these display wave like tendencies. They all have a wavelength and frequency. Anyway I have waffled on enough. If it were possible to identify the fundamental wavelengths of these systems it may be possible to tell when they move into or out of phase with each other and this I believe will be a fairly significant step towards longer term forecasting.