MELBOURNE, Australia – La Niña continues in the tropical Pacific, but is slowly weakening, reports the Bureau of Meteorology of the Australian Government in its latest update. However, while ocean temperatures have warmed in recent weeks, atmospheric indicators are largely unchanged, remaining at La Niña levels. La Niña typically increases the chance of above average rainfall for northern and eastern Australia during the summer.
Long-range forecasts suggest that tropical Pacific Ocean temperatures will continue to warm towards ENSO-neutral levels over the coming weeks, with some change in atmospheric patterns towards neutral levels also possible. As long-range forecast accuracy is generally lower at this time of year, ENSO outlooks that extend through autumn should be viewed with caution.
The Indian Ocean Dipole (IOD) is neutral and has little influence on Australian climate while the monsoon trough is in the southern hemisphere (typically December to April).
The Southern Annular Mode (SAM) is strongly positive and is likely to be positive until at least mid-January. During summer, a positive SAM increases the chance of above average rainfall for eastern New South Wales, eastern Victoria and north-east Tasmania and below average rainfall for western Tasmania.
The Madden–Julian Oscillation (MJO) has been in the Western Pacific since late December and is forecast to move into the Atlantic in the coming days. This may cause an easing in trade wind strength and increase cloudiness near the dateline, potentially weakening some indicators of La Niña.
Sea surface temperatures remain warmer than average in the western Pacific, much of the Maritime Continent, and around northern Australia. Warmer Australian waters, especially in the tropics, can result in greater evaporation, humidity, cloudiness, and rainfall.
Climate change continues to influence Australian and global climates. Australia’s climate has warmed by around 1.47 °C in the period 1910–2021. There has also been a trend towards a greater proportion of rainfall from high intensity short duration rainfall events, especially across northern Australia.
