Freak weather system dumps 100mm of rain AN HOUR on QLD, NSW: 'Very rare'

Australia’s southeast is dealing with scenes of destruction while two women and a child are lucky to be alive after an “incredibly unusual” storm swept across the coast on Thursday.

Residents in both northern NSW and southern Queensland suffered through a harrowing night as heavy rainfall, flash flooding and damaging winds lashed the states.

“We’ve seen a coastal trough with some upper level support crossing the east coast of NSW and southeast Queensland that has brought some pretty heavy deluges,” Weatherzone meteorologist Joel Pippard told Yahoo News Australia.

“In some locations, up to 200 millimetres fell in three hours which is a lot of rain.

“It's incredibly unusual for this time of year because September is actually the month where ocean temperatures are at their coldest so it's pretty rare to see this kind of rainfall at this time of year.”

Mr Pippard says a third straight La Nina weather event is largely to blame.

“The ocean temperatures are much warmer than normal over the Coral Sea area,” he explained, “so that would be the biggest driver I would think.”

Family pulled to safety from rising floodwaters

In the NSW Hunter region on Thursday, a dramatic police rescue saw a four-year-old boy pulled through the window of a vehicle stranded by rising floodwaters in Bingleburra.

A senior constable used a rope as a safety line on Thursday morning to reach the child and two women, one of whom’s foot had become trapped by a rock.

After rescuing the 51-year-old woman, the police officer used a winch to stabilise the submerged car before re-entering the floodwaters to bring the 44-year-old woman to safety.

All three were fortunately uninjured while the senior constable has been praised for his bravery.

Record rainfall in Queensland and NSW towns

The heaviest falls overnight were recorded in Upper Springbrook, in the Gold Coast Hinterland.

In just three hours before midnight, 222 millimetres of rain fell.

By 9am on Friday, 317 millimetres had been recorded in 24 hours.

While Clagiraba, further north in the Gold Coast's hinterland, notched up 104 millimetres an hour overnight.

“That is an incredibly heavy amount when we see 100 plus in an hour,” Mr Pippard said, “it’s very, very heavy.”

Since 9am on Thursday, more than 295 millimetres had fallen in the area.

It was a similar situation over the NSW border.

In just three hours, more than 222 millimetres of rain was recorded at Couchy Creek, leading to a total of 291 by this morning.

While in the Northern Rivers region of NSW, Grafton suffered through its wettest September day in 100 years with 48 millimetres in 24 hours.

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Although it’s not much in comparison, Mr Pippard insists it's “really unusual for September".

“Grafton is a reasonable way inland so this kind of rain at this time of year is very, very rare.”

Rain on the way for eastern Victoria

While the Bureau of Meteorology has on Friday morning cancelled the heavy rain warnings for NSW and Queensland, residents aren’t out of the woods just yet.

“So the majority of the heavy stuff is now offshore,” Mr Pippard said, “but we've still got lingering showers in its [the weather system’s] wake.”

Another connected low pressure system is also on its way, this time developing off the south coast.

“So for those areas that have currently got it, [they’re] probably looking at another five to 15 millimetres for the rest of today,” Mr Pippard explained.

“We’ll also see similar totals down in the south coast with the heaviest rainfall now in eastern Victoria, with about 20-40 millimetres to fall on Friday.”

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