It's back: third consecutive La Nina underway

It’s back: third consecutive La Nina underway

13 September 2022

The Bureau of Meteorology says Australia has entered a La Nina weather event, increasing the likelihood of floods this spring and summer.

It is the third La Nina in a row – and the last one only ended in June.

“Tropical Pacific sea surface temperatures have been cooling since June and are now at La Nina thresholds,” the bureau said today.

“Models indicate this La Nina event may peak during the spring and return to neutral conditions early in 2023.

“La Nina events increase the chances of above average rainfall for northern and eastern Australia during spring and summer.”

Meanwhile, a negative Indian Ocean Dipole (IOD) event continues and “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.

“When a La Nina and negative IOD combine, it further increases the likelihood of above average rainfall over Australia, particularly in the eastern half of the continent,” the bureau warns.

The Southern Annular Mode (SAM) is currently in a positive phase and is likely to be mostly positive for the coming three months. During the spring months, a positive SAM has a wetting influence for parts of eastern NSW and far eastern Victoria, but a drying influence for western Tasmania.

The bureau says 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.”