MELBOURNE, Australia – The Bureau’s ENSO Outlook continues at La Niña Alert, indicating at least a 70% chance of La Niña reforming later this year, reports the Bureau of Meteorology of the Australian Government in its latest update. This is around triple the normal likelihood. La Niña events increase the chances of above-average rainfall for northern and eastern Australia during spring and summer.
Neutral but cooler than average sea surface temperatures (SSTs) persist in the central and eastern tropical Pacific Ocean. Some atmospheric indicators, such as the Southern Oscillation Index and cloudiness near the Date Line, show a La Niña-like signal. Four of seven climate models surveyed by the Bureau suggest La Niña may return by early-to-mid spring.
The negative Indian Ocean Dipole (IOD) event continues. The IOD index has satisfied negative IOD thresholds (i.e. at or below −0.4 °C) since June, with the latest weekly value being −0.8 °C. All surveyed climate models agree that negative IOD conditions are likely to continue into late spring. A negative IOD event is typically associated with above average spring rainfall for much of Australia.
The Southern Annular Mode (SAM) index is currently positive and is likely to be mostly positive for the coming three months. During the spring months, a positive SAM has a drying influence for western Tasmania, with a wetter influence for parts of eastern New South Wales and far eastern Victoria.
The Madden–Julian Oscillation (MJO) is currently moderately strong in the western Indian Ocean. Most models suggest the MJO is likely to become weak in the coming days. A weak MJO is unlikely to have much impact on Australian climate.
Climate change continues to influence Australian and global climate. Australia’s climate has warmed by around 1.47 °C for the 1910–2020 period. Southern Australia has seen a reduction of 10–20% in cool season (April–October) rainfall in recent decades.There has also been a trend towards a greater proportion of rainfall from high intensity short duration rainfall events, especially across northern Australia.
