IN A slightly unexpected development, a combination of a couple of major North American models looking at expected trends in sea surface temperatures in the Pacific, shows weak La Nina conditions developing from late October/November into the early months of 2018 although weakening for January to March next year.
The subtropical North Pacific SST and the SST in many of the other extratropical regions are predicted to be above average during this time.
This means slightly enhanced probabilities for above normal precipitation are forecast for parts of eastern Australia from November to February at least.
It appears as though this trend will be more likely in eastern Queensland and the east and north-east of NSW with changes of above average rainfall lower in the west and south of the state.
As indicated previously, extended periods with neutral conditions make long range forecasting more challenging because of the potential for unexpected change so the confidence level of any long term prediction at the moment is a little lower than usual.
In the immediate future, little change is expected in the pattern that has dominated in the Australian region for the past couple of months although the influence of Southern Ocean lows and frontal system will continue to slowly decrease.
The Southern Annular Mode has been in a negative phase recently (resulting in stronger westerlies to our south) but it is expected to also head back to neutral in the coming weeks. This means mainly dry weather will dominate until at least the end of the month.
However, as indicated previously, other indicators point to some degree of optimism.
The south-east trades in the tropical western Pacific remain a little stronger than normal - indicating the possibility of a weak La Nina development and the Southern Oscillation index with its 30-day running mean sitting around +5 is still in the neutral range but towards the La Nina end.
So in summary, the dry weather will continue, butthere are positive signs for at least average rainfall in late spring and summer.
Given the expected developments, the chance of severe storms in late spring is a little higher than in an average year and the chance of late season frost in the first half of spring is also a little higher than normal but only marginally.