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Sydney weather: What’s causing staggering rainfalls

After torrential rain and flooding caused widespread havoc over swathes of Australia this summer, the wet weather looks stubbornly set to stick around.

Dr Karl Kruselnicki explained that La Nina is working together with other weather systems to create the perfect conditions for heavy rainfall, which could continue until at least late June.

Already this year, many towns and cities along the country’s east coast have reached their annual rainfall, including Sydney, which by early April had seen at least 1112mm of rain.

The average annual rainfall in Sydney is 1164mm, and there is still nine months of the year left go.

The deluge also caused devastating flooding in northern NSW.

Lismore was particularly hard hit with the entire town submerged and hundreds of homes severely damaged after the Wilsons River broke its bank and reached a peak of about 15metres twice in a month.

Bureau of Meteorology data from the last 13 La Nina events showing where has got the most rainfall. The NSW coast has historically been drier than inland but not in 2022

‘These weather events can be extremely dangerous. People can die. Buildings and infrastructure can be damaged. Just look at Lismore,’ Dr Karl told Today on the weekend.

He explained that the intense rain is being caused by ‘two pools of hot water up against our coast.’

‘La Nina on our east coast and on the west coast we have what they call the Indian Ocean Dipole and that is warm so it will evaporate.’

The beloved science presenter explained that the hotter water evaporates at a greater rate than normal which then sits in the upper atmosphere – eventually falling back down as rain.

Dr Karl said these two system were then combing with a third called the Southern Annular Mode. 

‘This is basically a bunch of cyclones continuously going around the South Pole’.

‘When they get snug in you get blizzards on the Antarctic, when they expand out you get cold weather patterns coming across Australia.’

He said this cold air causes low-pressure systems to travel up over Australia. 

When this collides with a high pressure-system ‘atmospheric rivers’ can form which allow water vapor to collect and be transported over vast distances. 

Dr Karl (pictured) said the wet weather could stick around until at least winter and possibly longer

Dr Karl (pictured) said the wet weather could stick around until at least winter and possibly longer 

Lismore on March 30 (pictured) was hit with a second record-breaking flood in the same month putting most of the town underwater

Lismore on March 30 (pictured) was hit with a second record-breaking flood in the same month putting most of the town underwater

Which so much moisture already in the air, Dr Karl, said this atmospheric river is what caused the deluge in Brisbane earlier this year and subsequent flooding on the northern NSW coast. 

‘That dumped eight cubic km of water on Brisbane in three days – that’s the equivalent of 16 Sydney harbours.’

As for when the rain will finally return to normal, Dr Karl bluntly said ‘we’re stuck with it in the short term’. 

‘For a couple of more months at least, it looks like it’s going to get worse. Maybe until June then things are up in the air.’

 According to the Bureau of Meteorology La Nina will subside in the next few weeks.

‘La Nina will ease in strength over the coming months, with a return to neutral ENSO conditions (neither El Niño nor La Niña) most likely in late autumn or early winter,’ BoM’s climate driver report said in April.

But overseas forecasters have painted a different picture saying the system could persist over Australia all the way through winter. 

La Nina is caused by wind pushing warmer surface water across the Pacific Ocean to Australian's east coast where it evaporates (pictured)

La Nina is caused by wind pushing warmer surface water across the Pacific Ocean to Australian’s east coast where it evaporates (pictured)

Weatherzone looked at data from the U.S. National Weather Service’s Climate Prediction Centre (CPC) and Columbia University’s International Research Institute for Climate and Society (IRI)

‘La Niña has a 59 percent chance of continuing through the Southern Hemisphere’s winter and a 50 to 55 percent chance of persisting thorough the Southern Hemisphere’s spring,’ it said.

The data also found that this summer’s La Nina was among the most powerful since 1950. 

Dr Karl added the driving factor behind the stronger than usual La Nina was climate change.

‘We can stop and reverse global warming which is the cause of it all we can drop our carbon emissions by 95 per cent in 10 years if we decide to,’ he said.

‘Whether we decide to or not depends on the influence of the fossil fuel companies.

Dr Karl said climate change was behind the particularly strong La Nina this year but said that it is reversible (pictured: Lismore in March)

Dr Karl said climate change was behind the particularly strong La Nina this year but said that it is reversible (pictured: Lismore in March)

‘We can reverse global warming and bring temperatures back to what they were in the 20th century.’

The rain isn’t the only climate problem the country is currently facing with warm, dry weather in Australia’s red centre sparking fire concerns. 

The Alice Springs region’s vegetation fuel load is huge and highly flammable after one of the wettest winters on record and a scorching summer.

‘In the desert, fire burns where water flows because that’s where fuel, in the form of vegetation, is heaviest,’ Charles Darwin University fire expert Rohan Fisher said.

Parts of Alice Springs were under a watch and act alert over the Easter long weekend, and fires west of the town of 25,000 could be seen from space.

Additional fire services have been flown to Alice Springs as a precautionary measure to help mitigate any additional risks.

Mr Fisher said even as the weather cooled it was important to be aware that the fuel load and fire risk remained.

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