Another localised rain event, this time affecting mainly the northern coast of NSW and parts of south east Queensland, passed through in the past week. As previously mentioned, such events are likely to continue and possibly become a little more likely in summer, but as each event affects a small area only, most parts of eastern Australia will continue with well below average rainfall.
This is because an El Nino pattern in the Pacific is well established. Although its effects have plateaued a little in recent weeks, the eastern Pacific sea surface temperatures continue to exceed El Nino thresholds, and with warmer than average water moving to the east beneath the surface as well, this will at least maintain this situation for some months, with SSTs remaining above El Nino thresholds into the southern hemisphere autumn 2024. As is typical with these conditions, rainfall throughout eastern Australia will be below normal for the majority, but not all of the coming months and temperatures, especially daytime maximum temperatures, will average out at well up on normal through most of spring and summer, although departures from normal will decrease the further north you go.
To the west, a positive Indian Ocean Dipole is now established but it appears to be fairly weak. However, all models indicate that this positive IOD will likely continue into early December at least, after which its effect on south east Australian rainfall decreases rapidly. In the meantime, a positive IOD typically leads to reduced spring rainfall for central and south east Australia and when a positive IOD and El Nino occur together, their drying effect can be stronger and more widespread across Australia, but this combination remains much weaker than it was in 2019-20, which is a good sign.
To the north, the Madden-Julian Oscillation is weak, but it is likely to strengthen during the first half of November. However, models diverge on where this strengthening will occur. Only a couple of models suggest the Western Pacific, which could increase coastal shower activity along the Queensland coast and north east NSW.
This feature, as well as the continued presence of unexpected warm waters in the Coral and Tasman seas which I have referred to previously, means that rainfall in coastal eastern Australia might not be as low as other parts of the country in the coming one to two months.
Finally, to the south, the Southern Annular Mode is neutral, and it appears likely that it will remain mostly neutral through most of November. This means the effect of the SAM index on south east Australian rainfall is likely to be minimal for the next five to six months.
