Cyclone Alfred has slowed down – why is that dangerous?

Tropical Cyclone Alfred has slowed its approach to the east coast of Australia, but meteorologists warn this brings added dangers, as its effects will batter South East Queensland and north-east NSW for longer.

The cyclone slowed and then stalled its progress towards the coast on Wednesday before again tracking west towards land on Thursday – albeit slowly.

Why has Cyclone Alfred slowed down?

Tropical cyclones are typically erratic weather systems, and Cyclone Alfred is no different. Weatherzone meteorologist Ben Domensino said cyclones were generally steered by broad high and low-pressure systems and could “wobble” – becoming more erratic – as they moved closer to the coast.

“As it moves close to the Queensland coast, it is starting to interact with some other areas of high and low pressure near eastern Australia, so that’s just causing it to wobble a bit as there are competing influences on the steering of the system,” Domensino said.

“[Tropical cyclones] can be very erratic and stray from the predicted path. But now that we’re getting closer and closer to landfall, there’s general consensus that it will move towards the coast. It’s just a case of how quickly.”

People are almost washed off the Brunswick Heads rockwall on the NSW north coast as Alfred moved closer.Credit: Nick Moir

Is it any less dangerous?

In a word, no.

Domensino said Cyclone Alfred’s slowed approach meant south-east Queensland and north-east NSW would be battered by extreme weather for longer – including heavy rains and storm surges before the cyclone hits the coast.

Of particular concern to affected communities is the heavy erosion taking place along coastlines in both states. The Bureau of Meteorology says dangerous surges between Cape Moreton and Yamba, including the Gold Coast and Byron Bay beaches, are likely, as is dangerous inundation of coastal low-lying areas.

Coastal erosion at the Brunswick Heads rockwall in northern NSW.Credit: Nick Moir

“We’ve got huge waves,” Domensino said. “We are seeing heavy showers, and that will just continue to deteriorate through Thursday afternoon and evening and throughout Friday as the system gets closer to the coast.

“We’ll see areas of heavy rain developing, particularly tonight [Thursday] into Friday, and we will continue to see waves building.”

Sustained rainfall before the cyclone hit land was also increasing the risk of major flooding, said Jonathan How, a meteorologist with the Bureau of Meteorology.

Even though Alfred remained off the coast on Thursday afternoon, more than 200 millimetres of rain had fallen in the 24 hours to 9am on the NSW Mid North Coast and in the Northern Rivers region.

Sandbags at Currumbin on the Gold Coast.Credit: AAP

In the Queensland hinterland, more than 100 millimetres fell in 24 hours.

“And this is actually wetting the ground before we see the worst of the rainfall come in,” How said.

Moderate to major floods are now predicted for communities in north-east NSW and South East Queensland as rain falls on already sodden earth.

“Now that the ground is very wet across NSW, that will be a particular concern with the tropical cyclone stalling,” How said. “We will see more rainfall building along the NSW coast before the system actually hits. And so there is definitely concern for the mid-north coast and Northern Rivers communities of NSW.”

NSW Premier Chris Minns said on Thursday that the cyclone’s slowed approach was creating headaches for emergency services.

“Unfortunately, that means the window for destruction in our community, [with] heavy rains, winds, powerful surf, is longer than we would otherwise like,” he said.

When is Alfred supposed to hit?

It’s possible Cyclone Alfred will perform another U-turn as it continues its wobbly path towards Queensland, but most experts expect it to cross the coast somewhere between Coolangatta and Maroochydore on the Sunshine Coast late on Friday or early on Saturday.

A business with taped windows in central Brisbane.Credit: Dan Peled

Weatherzone’s Ben Domensino said most modelling systems were struggling to predict with any certainty what time it would hit the coast due to Alfred’s erratic behaviour.

How long is Alfred expected to last?

Tropical cyclones weaken fairly quickly after they hit land, but Domensino said heavy rain could continue even after Alfred has weakened due to a remnant low-pressure system.

“This is a very dynamic system,” he said. “There’ll be severe weather impacts a long way away from the centre of the cyclone, and they’ll also continue for several days on either side of the tropical cyclone [hitting land], potentially.”

What is the latest safety advice for NSW and Queensland?

Tropical cyclone warnings are in place from Double Island Point in Queensland, south through the Sunshine Coast, Gold Coast, Brisbane and Northern Rivers, and down towards Grafton in NSW.

For the latest advice, visit the Bureau of Meteorology’s Tropical Cyclone Warning Centre.

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