Several months ago, even with the lack of cool water in the western Pacific, the eastern Pacific appeared to be in a clear El Nino state. This column expressed an awareness that this El Nino could be different because of the warm waters in the western Pacific and in the Coral and Tasman seas. In recent weeks, the El Nino sea surface temperature pattern in the Pacific Ocean seems highly "washed out". This mixed pattern of influences is contributing to decreased confidence in long-range outlooks.
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The sub-surface water in the western Pacific Ocean has caused the cool water pool to grow and extend eastwards, meaning the end of the current El Nino is expected earlier than originally thought. We are likely to see cooling occur in the eastern Pacific waters in autumn. However, it is clear this El Nino is now having minimal influence on our weather, so the timing of when the El Nino is officially declared over is less important for the longer-range outlooks. Instead, warm SSTs are likely to drive an elevated potential of rainfall into late summer and spring. In the longer term, most modelling appears to push towards a La Nina pattern next spring/summer, but there may be some variability yet to come. Strong monsoon pushes across northern Australia aren't normally followed by La Nina event, so the confidence level again remains reduced.
In the Indian Ocean, the Indian Ocean Dipole is technically still in a positive phase, but due to the warm SSTs occurring across the entire ocean it is effectively cancelling out any warm SST patterns in either the western or eastern Indian Ocean. The latest modelling guidance trends towards more neutral or even weakly negative IOD patterns into autumn and winter and early indications which would slightly encourage rainfall events in south east Australia by early winter.
The Madden-Julien Oscillation to the north has been in a favourable phase for rainfall across northern Australia since mid-January. The MJO is likely to maintain in a favourable phase until about mid-February when it should drift off, bringing a period of more stable conditions in the tropics during the second half of February. The current MJO has been one of the longest and strongest for some years
One thing that has been different compared to previous years has been that while rainfall has been very heavy in parts, the widespread nature of rainfall has not been quite as significant as previous years (notably 2022). Rainfall has largely been convective (thunderstorm), which provides more localised and potentially more intense rainfall, rather than widespread rainfall. This can mean some areas miss out on rainfall while others receive lots of rain.
