Fairfax Media Network

Weather News

La Nina declared heralding a humid, wet summer for Australia's east

Kate Doyle and Ben Deacon, Wednesday December 6, 2017 - 21:07 EDT
ABC image
Conditions are now officially at La Nina levels. - ABC

The Bureau of Meteorology has officially declared a La Nina in the tropical Pacific.

After weeks of slowly upping the scale, the Bureau's finally announced the climate phase on Tuesday.

Long range forecaster Dr Andrew Watkins said people on the east coast may notice more humid, tropical weather over the summer.

"Typically that would see us entering a wetter period for eastern Australia, and a bit cooler and more cloud as well," he said.

"December is kind of looking that way, particularly through southern Queensland, New South Wales, Victoria and even eastern South Australia as well."

Dr Watkins said to expect along the southern coast including Adelaide, Melbourne and Hobart.

The Bureau of Meteorology is quick to emphasise that this is a weak La Nina, and as such it is not expecting conditions like the 2010–12 strong La Nina event, which led to record-breaking rainfalls such as the 2011 Brisbane floods.

Why will this La Nina be weak?

"Normally the Indian Ocean gets quite warm when we get La Nina, at the moment it's close to average or even cooler than average," Dr Watkins said.

"The cooler Indian Ocean is counteracting the warm ocean temperatures in the Pacific and reducing the chances of above-average rain.

"Also the Southern Oscillation Index, the old one that a lot of farmers would know, that's only just getting above our thresholds at the moment for La Nina and ocean temperatures in the eastern Pacific are only just scraping over the thresholds as well."

Weak La Nina may bring heat waves

Dr Watkins said weak in the south of Australia.

"Keep an eye out for the long strings of days that are low 30s, rather than necessarily those short, sharp heatwaves that some of us are used to," he said.

The maintains above-normal fire danger for large parts of southern Australia.

Why has the La Nina been declared now?

Dr Watkins said this was an unusually late La Nina event.

"Typically La Ninas will form in the autumn and winter, so for one to form in spring or early summer is quite unusual," he said.

"And it tends to mean it probably won't hang around that long either."

Models suggest the La Nina conditions will last for the three months required to be declared a La Nina year before returning to normal in winter.


© ABC 2017

More breaking news

Sydney Morning Herald
ABC News
National Nine News
News Limited

Display Your Local Weather

Weather News

Channel Country gets three weeks' notice of floods after rain 700km away

06:49 EDT

Few landscapes allow for communities to have month-long flood preparations, but for Queensland's Channel Country floods can be predicted weeks in advance.

Tathra bushfire survivors huddled on beach as 'cyclonic' winds fanned destructive blaze

22:09 EDT

Steve Jory made it back to his home in Tathra, on the New South Wales south coast, in time to pick up his children and a few of the mementoes they had packed.

Tropical Cyclone Marcus clean-up continues, residents remains without power

19:45 EDT

Almost half the Darwin residents who lost power during Tropical Cyclone Marcus have been reconnected, but as clean-up efforts continue, the Bureau of Meteorology (BOM) has warned the Top End could see another cyclone this week.