THERE have been only minor changes in the many climatic indicators affecting Australia in the past weeks but the changes that have occurred have all leant towards an increased chance of above average rainfall over many parts of eastern and south east Australia in most of the months for the rest of the year.
To the west, the latest value of the Indian Ocean Dipole index is around 0.6deg.
The IOD has been below the negative IOD threshold (0.4) for a sufficiently long period to confirm the patterns are well established.
Most international models have the IOD remaining within negative thresholds until at least mid-spring, with neutral values returning by December when the IOD becomes less important anyway.
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In past years, when a negative IOD has occurred along with warmer sea surface temperatures in the eastern Indian Ocean off western and north west Australia. it generally increased the chances of above average late winter-spring rainfall for large parts of southern Australia and south/central Queensland.
A negative IOD also results in making slightly below average maximum temperatures more likely across southern Australia.
To our east, the El Nino-Southern Oscillation remains within the neutral range with most of the ocean and atmospheric indicators still neutral.
However, in recent times, the Southern Oscillation Index has increased out of the neutral range and the 30-day running mean is currently over +10.
However, it appears that this is mostly because local atmospheric pressure variations at Darwin and Tahiti.
Nevertheless, the trade winds are stronger than average in the tropical western Pacific. If this continues, there could be some temporary cooling of the SSTs in the eastern Pacific.
At this stage, this trend is not certain but now almost half of the international models which look at such things indicate this cooling will be enough to reach La Nina thresholds in spring.
If this continues to develop, then it may also contribute to an outlook for above average rainfall for much of Australia in the coming months as well.
As noted previously, there remains an increased chance of extreme random events occurring as the Earth's atmosphere gradually warms, as evidenced by recent events across parts of the northern hemisphere.
In Australia, with greater moisture availability from the negative IOD and from developing ENSO patterns in the Pacific, there is an increased chance of potential damaging weather events in spring and early summer, but such events will be interspersed by extended periods of stable weather.
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