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La Niña fades as El Niño returns to neutral, reports Australian Bureau of Meteorology (Bom)

La Niña Alert ENSO

MELBOURNE, Australia – The ENSO Outlook of the Bureau of Meteorology of the Australian Government has moved from LA NIÑA to INACTIVE as most El Niño–Southern Oscillation (ENSO) indicators have now returned to neutral levels. Climate model outlooks suggest the Pacific will remain at neutral ENSO levels at least until the winter. Tropical Pacific Ocean sea surface temperatures have persisted at ENSO-neutral values for several weeks.

Below the surface, much of the tropical Pacific is now at near average temperatures. Atmospheric indicators are also generally at neutral ENSO levels. The Southern Oscillation Index (SOI) is close to zero, while trade winds are currently being enhanced by the Madden–Julian Oscillation (MJO). Only cloudiness near the Date Line continues to show a weak La Niña-like signature.

These changes are consistent with climate model outlooks, which have indicated a return to ENSO neutral during the southern hemisphere autumn, with little indication of a return to La Niña patterns in the coming months. A return to ENSO neutral conditions in autumn is also typical of the life cycle of ENSO events. All models indicate ENSO will remain neutral until at least the end of the southern winter.

The Madden–Julian Oscillation (MJO) is currently the strongest climate driver influencing Australia. The MJO has moved into the Australian region at moderate strength and is expected to bring increased cloudiness and rainfall to far northern Australia and the broader Maritime Continent over the next week or two. This also brings an increased risk of tropical low/cyclone activity.

The Southern Annular Mode (SAM) is currently neutral and expected to remain neutral for the coming fortnight. A neutral SAM has little influence on Australian rainfall.

The Indian Ocean Dipole (IOD) is also neutral. The IOD typically has little influence on Australian climate from December to April.

Climate change continues to influence Australian and global climate. Australia’s climate has warmed by 1.44 ± 0.24 °C over 1910–2019, while recent decades have seen increased rainfall across northern Australia during the northern wet season (October–April), with more high-intensity, short-duration rainfall events. Southern Australia has seen a reduction of 10–20% in cool season (April–October) rainfall in recent decades.