TWO duelling weather systems are wreaking havoc on the east and west coasts of Australia in the dying days of summer.
Cyclone Rusty is battering the mining communities of north-western West Australia, floodwaters are peaking again in Queensland, and wet weather is threatening to return to Sydney.
Residents in the Pilbara are on a ''red alert'' as cyclone Rusty brought winds of as strong as 230km/h near its centre to the north-west of Western Australia.
The Bureau of Meteorology says people in Pilbara region towns between Pardoo and Whim Creek, including Port Hedland and South Hedland, should go to shelter immediately.
The cyclone is currently stationary but will resume its southward track and is expected to cross the east Pilbara coast late this afternoon, local time, said Grahame Reader, severe weather manager at the bureau's WA Tropical Cyclone Centre.
"It's still likely to be a cyclone by lunchtime tomorrow," Mr Reader said, adding that the storm's track is likely to see it reach the coast east of Port Hedland and head south between the Pilbara towns of Paraburdoo and Newman.
"Due to its strength and slow movement, it will bring very destructive winds, a very dangerous storm tide and major flooding," the bureau said in a statement.
The deputy mayor of Port Hedland shire, George Daccache, a resident of 40 years, expects the cyclone to be one of the worst the town has seen.
‘‘This one’s a bit of a beauty,’’ Mr Daccache said. ‘‘It’s going to be a pain waiting for two to three days for this to come and go."
The storm is also set to cause significant flooding in the Fortescue catchment and to Pilbara coastal streams, the bureau said.
This one’s a bit of a beauty
Port Hedland, which reportedly accounts for a fifth of world trade in iron ore with more than $100 million shipped each day, is no stranger to storms. Cyclone George reached category 5 status in 2007 in the region as did cyclone John in 1999.
Australia's Indian Ocean territory of Cocos Islands had a foretaste of the rain. It copped 416mm yesterday adding to the 415mm rain received on the two previous days - or more than Melbourne averages in a year.
Rusty's influence is being widely felt as it brings clouds and rain across the continent, reaching Victoria. "It's moisture streaming from Rusty," said Brett Dutschke, senior meteorologist at Weatherzone.
Combined with moisture coming off the Pacific, "it's the highest humidity we've seen this summer" across the country, Dr Dutschke said.
On the east coast, Gympie residents in south-east Queensland were preparing for their fourth flood in a year. About 34 businesses in Gympie were flooded after the Mary River broke its banks overnight.
Gympie Mayor Ron Dyne was inspecting the damage this morning after the river peaked at 18.44 metres about 2am (AEST).
‘‘It didn’t come up as fast and wasn’t as vicious (as last month’s flood),’’ he told AAP. ‘‘But we’re not breathing a sigh of relief.
‘‘People are just sick of it, we’ve had two floods in a month.’’
Further south, the State Emergency Service continued clean-up efforts across the northern coastal regions of NSW, with 54 communities still isolated after the weekend's wet and wild weather.
Warragamba Dam, Sydney's main water reservoir, is expected to continue to spill as forecasters tip more rain in coming days.
Weatherzone's Dr Dutschke said the dam's catchment was likely to receive at least 50 millimetres of rain between now and early next week, with falls of twice that amount possible.
''Rivers that have had flooding in the past week are likely to get further flooding,'' Dr Dutschke said. ''I wouldn't be surprised if the flooding is a bit worse to what has just occurred and that includes the Warragamba and the Nepean-Hawkesbury areas.''
The bulk of the rain will fall Wednesday and Thursday but showers will continue every day for the next week, adding about 15-30mm over the catchment, Dr Dutschke said.
The extra water, combined with inflows from other tributaries of the Hawkesbury-Nepean, had caused minor flooding to parts of Richmond and Penrith, a spokeswoman for the State Emergency Service said.
While the Hawkesbury-Nepean has not suffered a major flood since 1991, it remains one of Australia's most flood-prone regions, with about 120 floods recorded since European settlement.
Insurers said a major flood could cost billions of dollars because of large-scale residential development in the valley in recent decades.
The weather bureau on Tuesday downgraded the threat of more flooding for the Hawkesbury-Nepean system.
Sydney's wettest days are expected at the weekend before the weather clears up.
Weatherzone is owned by Fairfax Media, publisher of this newspaper.