Weather bureau declares La Nina over but wet conditions to persist

The La Nina weather system that brought record-breaking rainfall and floods to Australia over the past year is over, but forecasters say there is a 50/50 chance the system could return later this year.

The Bureau of Meteorology said it had observed the 2021-22 La Nina weakening over several weeks and declared it over on Tuesday following changes in sea temperatures and winds in the Pacific Ocean.

The BoM says there’s a 50 per cent chance the weather event could return later this year.Credit:Jason South

“[These] all indicate we are moving back into neutral conditions,” BOM’s long-range forecasting head, Andrew Watkins, said.

However, Watkins said models now suggested there was about a 50 per cent chance of a La Nina system returning later this year and the bureau had shifted its forecast for the system to a “watch” status.

“About half of the models we survey suggest we could return to La Nina in the spring,” he said.

A three-year La Nina would be uncommon, according to the bureau, occurring only three times since the middle of the last century.

A shift away from La Nina is also unlikely to put a stop to wetter-than-average conditions for winter and spring due to the persistence of other climate drivers.

A developing Indian Ocean dipole – a similar event to the El Nino/La Nina patterns that typically brings wet conditions to central and southern Australia – and warm ocean temperatures off Australia’s north and west coasts will continue to bring above-average rainfall, Watkins said.

“Those warmer ocean temperatures tend to bring wetter-than-normal conditions to much of Australia,” he said.

Last summer was the wettest for Sydney in 30 years, while humidity in Melbourne reached record levels through January.

January was also Victoria’s eighth-wettest on record and its wettest since 2011, when the last La Nina event occurred.

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