ONE of the features of the weather patterns in recent months has been the tendency for the synoptic patterns in the Australian region to semi-stagnate for extended periods of time.
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One of the reasons for this has been the lack of significant jet stream movements in the Australian region and the lack of the monsoonal activity in the north and north-west of Australia has been another feature.
This semi stagnation has brought extended periods of stable weather in the south-eastern states and the occasional burst of a week or more of very wet weather in parts of northern Queensland.
It was also responsible for the excessive heat in January and relative mild mid to late February weather in NSW and Victoria in the last couple of weeks.
So the important question is whether this type of synoptic pattern will persist into autumn.
It is usual for the jet stream to pick up in autumn, especially the second half of the season so it might be at that time we will start seeing a change that could lead to more unsettled weather but in the immediate future there appears little prospect for significant change to the slow moving patterns of recent months.
More very warm to hot conditions are likely in the south before the season is over and it is likely that any rain events in the coming month will be patchy and variable and some areas will continue to miss out.
It is too early to tell whether the patterns of recent years, which have seen a decrease in rainfall in the south and south-east of Australia is part of a longer term trend or linked to climate change.
The fact that air and ocean temperatures in the Australian region have risen by an average of one degree in the past couple of decades has put more “energy” into the atmosphere and that occasional but more severe events are likely to continue to be more frequent.
This could mean that in NSW, Victoria and southern Queensland, we might have to adjust to a decrease in average rainfall – especially in the winter months of about 10 to 20 per cent and an increase in summer temperatures but much more work and analyse has to be carried out before there is any level of confidence in these predictions.
In the mean time it appears as though autumn rainfall this year might be close to average along the east coast, but continue below average inland and in the south and that autumn temperatures will be a little up on normal but not as significantly high as they were in summer.
