It may be time to start dusting off the gumboots, because it looks like we may be in a for a very wet Spring and Summer.
The Bureau of Meteorology has officially declared that La Niña has developed in the Pacific Ocean, with the weather bureau today upgrading their initial alert to an active event.
This means that recent changes in ocean temperatures and weather patterns over the Pacific are now likely to remain until at least the end of the year.
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“Recent observations and model forecasts show the central tropical Pacific Ocean is now 0.8°C cooler than normal, and that has resulted in changes to Trade Winds and pressure patterns,” Bureau Manager of Climate Operations Dr Andrew Watkins said.
La Niña is a phase of the El Niño Southern Oscillation, which is associated with cooler than average sea surface temperatures in the central and eastern tropical Pacific Ocean.
The event typically results in above-average spring rainfall for Australia and can also mean cooler days, more tropical cyclones, and an earlier onset of the first rains of the wet season across the north.
The last major La Niña event occurred from 2010-2012 and resulted in one of Australia’s wettest two-year periods on record, with widespread flooding occurring in many parts of the country.
Mr Watkins said it’s likely this year will not see the same intensity as that La Niña event, but is still likely to be of moderate strength.
“This year we are probably not going to have something as extreme as that event, but having said that, be aware of local impacts like flooding, heavy rains, possibility of storms can occur at anytime during La Niña,” he said.
The Bureau has confirmed that #LaNiña has formed in the tropical Pacific, with climate models suggesting it’s likely to remain until at least the end of 2020.
— Bureau of Meteorology, Australia (@BOM_au) September 29, 2020
Residents living in the North East, which includes northern NSW and all of Queensland, are being warned to expect above-average rainfall with a potential for increased flooding.
“The potential for more tropical cyclones crossing the coast increases in the far north-east during La Niña events,” Watkins said.
“We’re also likely to see the first rains of the northern wet season kick in a little earlier this year because of the La Niña… We typically see that monsoon trough move down over Queensland and into parts of the northern territory as well a little earlier.
“So yes, we need to be prepared for more tropical cyclones, earlier tropical cyclones and also wetter conditions over the coming months, the risk of flooding is increased as well in many areas,” he added.
The South East of the country, which includes Tasmania, Victoria, South Australia and New South Wales, generally experiences wetter than average conditions during La Niña.
“During La Nina, South Eastern Australia typically gets more rainfall during spring and into summer… This can wet up the soils and make the chance of widespread flooding events higher during a La Nina event. So typically, more rainfall, wetter soils, higher rivers, and increased flooding,” Watkins said.
La Niña events normally last for around a year, however they can be shorter, or much longer.