Unusual weather patterns persist in south east Australia with the synoptic patterns to some extent reflecting the overall guidance of the longer term climate models. Many rivers are in flood and all NSW dams greater than 90 per cent capacity so it requires only light to moderate rainfalls to put a new flood crest down most rivers in NSW, Victoria, northern Tasmania and south east Queensland, such has been the widespread nature of recent rain events.
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In the Pacific, the La Nina event remains entrenched at the moment and it is increasingly likely that it will continue into 2023 but gradually weaken. As noted previously, both the sea surface temperature patterns and the atmospheric indicators such as the Southern Oscillation Index all indicate a well-established La Nina event. The current 30-day running mean of the SOI is still high at around +19 and latest daily values show only a very slow decrease. It is likely that it has reached its peak at the current time and should gradually weaken in the late spring and into summer. Latest models indicate it could be autumn before the SST patterns in the Pacific return to ENSO neutral.
To the west there has been little change to the current set-up with a negative Indian Ocean Dipole set to persist into summer, at which time it becomes irrelevant as a climate predictor until around April. Consequently, it will continue to contribute to above average rainfalls in the eastern third of the continent for some time to come.
As is often the case at this time of year other indicators are showing little change but contributing to the current wet weather. (It was as recently as 2019, when all main indicators - the ENSO in the Pacific, the IOD and to the south the Southern Annular Mode were all the opposite to what we have now and no doubt sometime in the future this will occur again.)
The SAM is still mostly positive, although this could briefly change in the coming week with westerly winds briefly pushing further north. However, in the summer months, a positive SAM increases the chance of above average rainfall for parts of eastern NSW, eastern Victoria, and south-eastern Queensland, as it often exists in conjunction with the Pacific La Nina.
Finally, to the north, a pulse of the Madden-Julian Oscillation has strengthened as it moved through western Pacific. Most climate models predict it will remain moderate in strength and move slowly east. At this time of the year, it mainly affects the northern Queensland coast but on occasions it can increase the chance of above-average rainfall across parts of eastern Australia as well.
