Wednesday 19 June 2024
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Tropical Pacific Ocean likely to cool, but remain Enso – neutral, says Bom update

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MELBOURNE, Australia – The El Niño–Southern Oscillation (ENSO) is currently neutral, reports the Bureau of Meteorology of the Australian Government in its latest update. Sea surface temperatures (SSTs) in the central tropical Pacific Ocean are near average, despite slowly cooling over the past two months. Waters beneath the surface are slightly cooler than average.

While most models indicate SSTs in the central tropical Pacific are likely to continue cooling over the coming months, ENSO-neutral is favoured to persist. Only two of the seven models surveyed suggest SSTs will remain cool for long enough to be considered a La Niña event. This cooling of the tropical Pacific may be contributing to the wetter than median climate outlooks in Australia.

Most climate models predict the negative Indian Ocean Dipole (IOD) event will persist through the southern hemisphere spring, despite current values rising marginally above the −0.4 °C threshold. Stronger-than-usual easterly winds across the tropical eastern Indian Ocean over the last three weeks have weakened the IOD event, however, this is most likely to be temporary. A majority of the five climate models surveyed by the Bureau predict the negative IOD will persist into November. A negative IOD increases the chance of above average winter–spring rainfall for much of southern and eastern Australia.

The Madden–Julian Oscillation (MJO) is currently in the western Indian Ocean, where it has remained since early August. This phase of the MJO typically sees increased cloudiness over the Southeast Asian parts of the Maritime Continent and eastern Indian Ocean, along with enhanced easterly wind anomalies, which may have acted to weaken the negative IOD. Forecasts generally indicate a weak MJO will progress eastwards across the Indian Ocean in the coming week.

The Southern Annular Mode (SAM) index has been positive over the past week and is forecast to remain so for the next fortnight. A positive SAM typically has a drying influence on south-west and south-east Australia during winter, and enhances chances of above average rainfall over much of New South Wales during spring.

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


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