The long term climatic indicators that have been used successfully at times in recent years in order to predict weather developments, are going through a transition period.
In other words, they are not strongly indicating anything – and as a result the longer term predictions are going through a period of considerable challenge with a lower than usual confidence level associated with outlooks.
Recently, a relatively new “weather index”, the Southern Annular Mode (SAM), which describes the north–south movement of the westerly wind belts that circle the South Pole, has had a stronger than normal influence on our weather, keeping the high pressure belts around southern Australia and thus, preventing the strong Southern Ocean fronts, typical in a normal winter, from penetrating north.
The polar circulating long wave troughs are also unhelpful – stagnate in the far east Indian Ocean and east of New Zealand with a stable upper ridge over eastern Australia.
All systems appear to be slowly moving with the SAM forecast to be negative by July, which would then allow the Southern Oceans fronts further north.
Once that happens, then all eyes will go to the Indian Ocean Dipole (IOD) because even a slight negative IOD will encourage NW cloud bands. These strips of upper level moisture can be activated by stronger Southern Ocean fronts to bring much needed rain events to the south eastern states. But be-warned : They all have to come together for it to be worthwhile.
As this is only going to happen occasionally, then the favoured scenario remains for just the occasional rain event – helping in places. However, below average rainfall will continue in areas not effected. The prospects for spring remain on the dry side, as well, with a possible “El Nino” returning by November.
