Australia is now on a La Nina watch, the Bureau of Meterology has declared, and there are signs the climate driver, which generally results in above-average rainfall over much of Australia, may form later this year.
La Nina is the positive phase of the El Nino Southern Oscillation and is associated with cooler than average sea surface temperatures in the central and eastern tropical Pacific Ocean, according to the Bureau of Meterology.
It is normally associated with higher than average winter, spring and early summer rainfall over much of Australia.
“La Nina tends to begin in autumn, mature during winter, spring and early summer, then begin to decay in late summer,” the Bureau of Meterology’s website reads.
“La Nina generally ends in the autumn.
“The greatest impact usually occurs during the winter, spring and early summer period
“La Nina normally lasts for around a year; however, they can be shorter or much longer.”
Sky News meteorologist Rob Sharpe said most models were picking La Nina to form by August, and it would also increase the flood risk, typically in the second half of the year.
“Historically, it’s brought wetter than usual weather to the country, but it’s not our only climate driver that is active at the moment or likely to be active,” Mr Sharpe said.
“Through winter, drier than usual weather is likely for the northwest and for the southern coastline and there’s only a small tendency towards wetter than usual for parts of the east of the country.”
Mr Sharpe predicted normal” rainfall throughout winter with temperatures “well above the usual”.
“But as we move into spring I think we will have more of an influence from La Nina and more rainfall starting to get going,” he said.
The Bureau of Meterology said conditions in the tropical Pacific Ocean were neutral, and while there were some signs that a La Nina may form in the Pacific Ocean later this year, there was a similar likelihood that the tropical Pacific Ocean would remain neutral.
“Moving to La Nina watch does not mean that the bureau is declaring that a La Nina event is under way,” the Bureau of Meterology said in a statement.