The majority of models predict an easing of the La Nina early next year,which suggests a relatively short-lived event. BOM forecaster Jake Phillips said the event is likely to be weak to moderate.
The wet weather will linger throughout spring with the negative Indian Ocean Dipole (IOD) and the Southern Annular Mode compounding the wet weather across the country. Phillips said the three climate drivers interacting with one another doesn’t occur that often.
This is the first time on record that Australia has experienced three consecutive La Nina events coinciding with back-to-back negative IOD events. Australia has experienced 20 La Nina events since 1900 and 12 have coincided with flooding in eastern states. The average rainfall from December to March in La Nina years is 20 per cent higher than the long-term average.
The country has only experienced three back-to-back La Nina events three times since records began,Phillips said.
“Most of the time,we only get one La Nina year and then it swings back[to neutral],” he said. “In the eastern part of Australia,we should prepare for more rain than average in spring and the first half of summer.”
Australia was one of the last countries to declare the La Nina event,with international models showing the climate event had already begun earlier this year. This is because international weather agencies use different thresholds to measure La Nina. In Australia,the BOM measures sea surface temperatures over the Pacific Ocean around the country’s coastline.