Third La Niña declared in a row, with Bureau of Meteorology expecting 50mm of rain to fall in coming month

For the first time in more than 20 years, a triple La Niña season has been declared with the Bureau of Meteorology making a grim forecast about rain and cyclones.

A La Niña wet season has been officially declared for the third year in a row - a situation not seen for 22 years and one that’s set to bring more rain and higher cyclone activity.

While this means eastern Australia is unlikely to face the devastating bushfires as experienced in 2019, the Bureau of Meteorology has warned the atmospheric phenomenon will be similar to the last La Niña period.

BoM senior forecaster Mosese Raico said eastern Australia would probably face significant impacts like flooding while northern Australia was at risk of cyclones.

A cyclist rides across Casuarina Coastal Reserves’ Rapid Creek Bridge as Darwin entered cyclone watch in February this year. Picture: Glenn Campbell

“The chances of seeing above average rainfall is increasing,” Mr Raico said.

“There’s an average to above average chance of seeing more numbers of those cyclones around the tropical borders.”

Mr Raico said the period from May 1998 to March 2001 was considered the longest La Niña phase - until now.

Nightcliff Foreshores seagulls enjoying some left over chippies on the roof of a car during the peak of the last monsoonal season. Picture: Glenn Campbell.

Mr Raico said the northern rainfall onset was likely to commence in early October and it would encompass the north and north-western parts of the Top End.

“Without La Niña it would normally be around the middle of October,” he said.

“The actual monsoon onset instead of being between Christmas and New Year’s during non La Niña years, with this La Niña that start can be shifted about one to two weeks earlier potentially before Christmas.”

Mr Raico said the rainfall predicted for the coming three months was forecasted to be average to above average in the Top End and eastern parts of the central districts.

“I know it was a little bit disappointing in rainfall (last year) across northern parts of the Territory,” Mr Raico said.

Large parts of the Top End, around the Gulf of Carpentaria, and northern to central Queensland have more than twice the average chance of unusually high rain in October to December.

Meanwhile, this week’s weather will fluctuate between dry and humid conditions with September generally a “transition month” between the wet and dry season.

“Seeing as we’re in September, we could see the first 50mm accumulated total being reached over parts of the north western Top End potentially by the beginning of October,” Mr Raico said.