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El Niño–Southern Oscillation to remain neutral for at least the coming six months, says Bom

El Niño negative Indian Ocean Dipole

MELBOURNE, Australia – The El Niño–Southern Oscillation (ENSO) remains neutral and climate model outlooks show this neutral ENSO state is likely to continue for at least the coming six months, says the Bureau of Meteorology of the Australian Government in its recent update. Oceanic indicators of ENSO are clearly within the neutral range, with sea surface temperatures across almost all the equatorial Pacific Ocean close to the long-term average. Similarly, temperatures beneath the surface show no significant shift away from normal.

Atmospheric indicators, such as the Southern Oscillation Index (SOI) and cloud patterns, are well within the ENSO-neutral range. Trade winds are generally ENSO neutral, although currently stronger than usual in the far western Pacific due to an approaching pulse of the Madden–Julian Oscillation.

A moderate to strong pulse of the Madden–Julian Oscillation (MJO) is currently in the Maritime Continent region. It is forecast to move eastwards towards the western Pacific and weaken. At this time of the year, the MJO influence is shifting to the northern hemisphere, and therefore has less influence on northern Australia. When the MJO is active over the eastern Maritime Continent and western Pacific region, increased cloudiness and rainfall is likely over parts of South-East Asia, the western North Pacific, Papua New Guinea and the northern Solomon Islands.

The Southern Annular Mode (SAM) index has recently become negative after being at positive levels for a fortnight. It is expected to remain negative for the coming week before increasing to neutral values over the following week. Negative SAM typically acts to increase rainfall over southwest and southeast Australia and reduce rainfall over parts of eastern Australia. Neutral SAM has little influence on Australian climate.

The Indian Ocean Dipole (IOD) is currently neutral, although the index has dropped in the past week. Large parts of the eastern Indian Ocean are warmer than average, with some cooler than average water near the Horn of Africa. Climate model outlooks suggest the IOD is most likely to remain neutral during winter, although two of the five models suggest negative IOD conditions could develop in the next three months. However, it should be noted that accuracy of IOD forecasts made during autumn have lower accuracy than at other times of the year, with accuracy improving in winter. A negative IOD increases the chances of above average winter-spring rainfall for southern Australia.

Climate change continues to influence Australian and global climate. Australia’s climate has warmed by 1.44 ± 0.24 °C over 1910–2019, while southern Australia has seen a reduction of 10–20% in cool season (April–October) rainfall in recent decades.