Grab your brollies and sandbags: Weather bureau declares La Nina is back
The Bureau of Meteorology has confirmed what many have dreaded – a third consecutive La Nina has become established.
The bureau announced today that key atmospheric and oceanic indicators of the El NiƱoāSouthern Oscillation show an established La NiƱa, which was likely to mean a wetter Spring but potentially revert to neutral condition in early 2023.
However, the La Nina would also be occurring in the Pacific at the same time as its counterpart in the Indian Ocean, which also produces more wet weather for the east coast.
A triple La Nina is not common and only three have occurred since the 1950s.
Adding to the concern over a third La Nina is that many dams are already at or near capacity and much of the ground in eastern Australia remains damp from a wetter the normal winter which could lead to more extensive flooding.
āTropical Pacific sea surface temperatures have been cooling since June and are now at La NiƱa thresholds. Atmospheric indicators including the Southern Oscillation Index (SOI), trade wind strength, and equatorial cloudiness are also displaying patterns typical of a La NiƱa event,ā BoM said.
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It came as the Brisbane City Council announced it would be giving away sand bags more than a month before the wet season normally occurs and workers had already prepared 150,000 bags in preparation for La Nina.
BoM said its models indicated this La NiƱa event may peak during the spring and return to neutral conditions early in 2023. La NiƱa events increase the chances of above-average rainfall for northern and eastern Australia during spring and summer.
āThe negative Indian Ocean Dipole (IOD) event continues. The IOD index has satisfied negative IOD thresholds (i.e. at or below ā0.4 Ā°C) since June, with the latest weekly value being ā0.8 Ā°C.
āAll surveyed climate models agree that negative IOD conditions are likely to continue into late spring. When a La NiƱa and negative IOD combine, it further increases the likelihood of above average rainfall over Australia, particularly in the eastern half of the continent.
āClimate change continues to influence Australian and global climate. Australiaās climate has warmed by around 1.47 Ā°C for the 1910ā2020 period. Southern Australia has seen a reduction of 10ā20% in cool season (AprilāOctober) 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.ā
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