The dreaded weather system behind heavy downfall and devastating flooding will end in spring, but summer will bring new challenges and surprising forecasts.
As the negative Indian Ocean Dipole (IOD) in the west ends, the La Nina weather event in the east will continue to create wet weather going into the holiday season and beyond.
But to understand what this means in terms of weather over the silly season, we need to understand what all these weather events are.
Climate drivers are events caused by the oceans surrounding us and the atmosphere above us, which all have the ability to greatly impact the weather.
The Indian Ocean Dipole
Otherwise known as the IOD, the Bureau of Meteorology says this climate driver event in the Indian Ocean is “defined by the difference in sea surface temperature between two areas” or poles, hence “dipole”.
The IOD is divided into three main categories – negative, neutral and positive.
In neutral years, the IOD has little impact on the climate around us, but negative years bring heavy rainfall to the countries on the eastern side of the Indian Ocean and droughts to the west.
A positive IOD event creates the opposite effect – the chance of drought and, in extreme cases, roaring bushfires.
Take the positive IOD event in 2019 when Australia suffered through one of the most devastating bushfire seasons on record.
In simple terms, what’s affecting us right now is a negative IOD, where the water cycle brings heavy rainfall and cold winds.
The negative IOD often coincides with La Nina to push more rain across the country.
The bureau says the negative IOD will continue into late spring “before rapidly decaying”.
La Nina and El Nino
Like the IOD, the La Nina and El Nino weather events are opposite ends of the scale, with a neutral middle being normal weather conditions.
La Nina and El Nino occur when the Pacific Ocean and surrounding atmosphere changes from its normal state.
In an El Nino event, the central and eastern tropical Pacific warms up, and La Nina is the opposite, bringing cooler conditions.
During these events, the ocean temperature becomes warmer than usual or cooler than usual.
Like a positive IOD, the El Nino event brings warmer weather and less rainfall, while the La Nina – what we’re experiencing now – brings cool winds and heavy rainfall, providing an explanation for the devastating flooding across the country’s eastern states.
A typical La Nina period would be expected to end over summer or in early autumn, but as this is the third La Nina in a row, it could be relatively short, leading meteorologists to believe it could be over in January/February next year.
So, what does this mean for the coming months?
The bureau’s senior meteorologist Jonathan How on Wednesday told the Today show that the La Nina event was expected to end in January.
“We are still expecting to see increased rainfall and flooding risk into summer, but heading into early 2023, this La Nina looks like being over,” Mr How said.
“Heading into this La Nina, we were very confident it would be a shorter one compared to the two previous ones which dragged on. Yesterday’s update really confirmed that.
“It will be a shorter one but still expecting to weaken off early in 2023. Some models say December, but others say neutral conditions in February.”
Mr How said it was likely the stormy, flood-inducing weather would continue for some time to come.
“Widespread flooding beyond what we have already seen is a possibility,” he said.
The wet summer ahead is expected to bring heavy rainfall to northern Australia, South East Queensland and northern NSW.
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