La Niña Event Declared as Australia Prepares

Australian meteorologists have declared a La Niña weather event associated with wet conditions for eastern and northern Australia over summer.

Bureau of Meteorology (BOM), today said the Pacific Ocean was in a La Niña phase.

BOM head of operational climate services, Dr. Andrew Watkins says the La Niña is expected to persist in eastern, northern and central parts of Australia until at least the end of January 2022.

He said la Niña will bring more rain to river catchments that are already at their capacity.

“We have seen a relatively wet spring, it could be our coolest spring since 1999 and it is looking like the wettest spring since 2011,” Dr. Watkins told reporters in Melbourne on Tuesday.

“Because of the conditions we’ve seen over the last couple of months, making the landscape very wet, we are at risk of more widespread flooding than usual,” he added.

The last significant hit in Australia was 2010 to 2012, leading to the nation’s wettest two years on record, with widespread flooding.

“Last year we saw a weak to moderate La Nina event. Now we’re backing that up with a weaker La Nina event,” he said.

“A weak La Niña can still bring heavy rainfall at times. With a wet landscape we are at risk of more widespread flooding over the summer.”

BOM senior meteorologist Dean Narramore said “Flood watches have already been issued for SA and we’re likely to see flood watches also issued for parts of northern and eastern Victoria and much of inland NSW either today and tomorrow.”

Over the next four days widespread falls of 50-100mm in those areas expected.

During the next four days, he said eastern Queensland, eastern and central NSW, and Victoria’s north and east could receive between 50 and 100 millimeters of rain.

What is La Niña and How it Affects Australia’ summer

During a La Niña event, strong trade winds blow west across the Pacific Ocean, pushing warm surface water towards Asia and the northern seas of Australia. The warmer waters lead to increased rainfall across northern and eastern Australia.

A map of the Pacific ocean with a clockwise circle of arrows indicating strong air flow and increased convection over the west.

“Those weather patterns shift cloud and shift rainfall towards Australia, so we tend to get a wetter spring and also a wetter a summer, at least in earlier parts of summer,” Dr. Watkins said.

In Australia, El Niño or La Niña conditions have the strongest influence on how the climate varies year to year. They belong to a cycle known as the El Niño-Southern Oscillation, which has an irregular timescale of several years.

“Last year we saw a weak to moderate La Nina event. Now we’re backing that up with a weaker La Nina event,” he said.

“A weak La Nina can still bring heavy rainfall at times. With a wet landscape we are at risk of more widespread flooding over the summer.”

Narramore said parts of Victoria, Queensland and NSW would be lashed with heavy rain and thunderstorms from Wednesday.

Update for the week

By Wednesday, the focus of the rain and storm activity will be through inland parts of Queensland, Western NSW and eastern SA.

But Thursday is the main day of concern, with areas of heavy rain across northern Victoria, west of the ranges in NSW and much of southern inland Queensland.

On Friday the rain will be focused over eastern Queensland, eastern and central NSW and possibly parts of northern and eastern Victoria, according to Mr Narramore.

Over the next four days widespread falls of 50-100mm in those areas expected.

And Saturday rain and storms likely contract to northern NSW and Queensland.