Some signs around the middle of October have indicated the El Nino conditions in the central-eastern equatorial Pacific appear to have plateaued at the level of a moderate El Nino event. Previously, it looked likely a strong event was developing. However, both the oceanic and atmospheric variables are now consistent with a moderate El Nino event.
Despite this, almost all of the major international models forecast a continuation of this El Nino event during the rest of 2023, all of summer and into early autumn of 2024, with a subsequent weakening thereafter.
However, ENSO neutral conditions are not likely to become the most dominant category until late autumn or early winter next year. This means the likelihood of below average rainfall in eastern Australia will continue to be the favoured scenario for many months.
That said, the fact this event has plateaued a little earlier than expected means any further changes in the coming few weeks could see this prognosis change a little.
Of also of note, as I have mentioned previously, is the continuation of slightly warmer than normal water in the tropical western Pacific as well as large parts of the Coral Sea and Tasman Sea.
This appears to have been partly responsible for an early season tropical cyclone developing near the Solomon Islands but these SST patterns could also assist in the occasional rain event in parts of eastern Australia during an otherwise drier than normal season.
Also, to the west the changing temperature patterns in the Indian Ocean when the monsoon season starts are likely to see the Indian Ocean Dipole (IOD) return to neutral in December and therefore no longer adding its support to the Pacific El Nino event. This means moisture deficiencies would decrease in the second half of summer.
Regardless of these possible changes which give some hope on the rainfall front, it remains very likely that above average temperatures will continue to be a feature for the rest of this year and throughout summer.
More extreme anomalies will tend to move away from NE NSW and Queensland and be more significant in southern NSW, Victoria and the SE of South Australia by the end of the year. The highest bushfire threat will move accordingly.
Beyond next autumn, conditions should return to a more neutral pattern. Neutral conditions are favoured in the Pacific in winter and there is even a 25 per cent chance that a La Nina could be forming by around July. This far out, however, this prognosis is a little speculative.
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