There are likely to be widespread falls of 100-150mm on Sunday and Monday, and "in some parts it will be more", Mr Zmijewski said. Collaroy's beach front houses were among those hardest hit by this year's big storm. Credit:AAP At present, the bureau's four-day rain forecast from June 18 onwards suggests the state's south coast is in for a soaking while Sydney too may also collect as much as 100mm of rain. (See chart below.) For Sydney, the updated forecast points to the city receiving as much as 60mm of rain on Sunday, while coastal towns such as Bega may collect as much as 40mm on Sunday and 120mm on Monday.

Brett Dutschke, a senior meteorologist at Weatherzone, said models were still to "get a grip" on the timing and location but another east coast low is looking increasingly likely. "Where the biggest wind, surf, rain and beach erosion will be is difficult to tell," Mr Dutschke said. While the potential winter storm is unlikely to be as widespread or as long-lasting as the monster east coast low that hit the state at the start of June, catchment areas will be sodden and many beaches have already been stripped of their protective sand buffers. "It's likely there'll be some beach erosion, with damaging surf and wind," Mr Dutschke said, adding that coastal impacts may be from next Monday onwards. The aftermath at Collaroy Beach even after 12,000 sandbags were laid. Credit:Peter Rae

Storm preparation Authorities may also want to expedite the removal of any debris from the previous storm, Mr Dutschke said. "You don't want to have (that debris) lying around in rivers or gutters," Mr Dutschke said. "You want that water to running as freely as possible from the rivers out to the sea." The worst coastal erosion impacts occur when there are a series of storms over a short period of time Office of Environment and Heritage Angus Gordon, a coastal engineer, said there was "very little people can do to protect against wave action at this late stage", noting that effective seawalls could take months to plan and build.

"There are vulnerabilities up and down the coast," Mr Gordon said. Still, people who live in areas facing possible inundation from wild seas or flooding rivers should consider taking prized possessions such as photographs and other memorabilia to safer locations. "People are often most upset" about such losses after a storm, he said. Warm waters The bureau's Mr Zmijewski said a dominant high-pressure system over the Tasman was leading to the relatively warm temperatures across eastern Australia. Tasman Sea waters were easily the warmest on record, according to bureau data for May. Unusually warm sea-surface temperatures off south-eastern Australia have the potential to give storm systems extra moisture. The ocean warmth "is another very important factor", Mr Zmijewski said .

(See chart below showing the pocket of unusual warmth just off Sydney.) While most catchment areas are particularly wet after the previous event, the likelihood of more rain will see some reservoirs start to spill, Mr Dutschke said. Warragamba Dam, Sydney's major water storage, was sitting at 97.7 per cent full as of Monday, the government's website said. The 24 hours to 9am on Sunday, June 6, was the wettest day on record for eastern NSW, with 19 of the state's 20 coastal catchments recording at least 70mm of rain, the bureau said. On the plus side, many inland regions of NSW and Queensland can expect more good rainfall as the system moves eastwards, the meteorologists said.

Record waves June is typically the most active month for east coast lows, cyclonic systems that form off the eastern Australian coast and bring heavy rain and storm surges if they linger near land. Authorities are still assessing the full impact of the previous storm that caused widespread damage from south-eastern Queensland down to Tasmania. At this stage, the coming event is expected to be faster moving, resulting in more localised heavy rain and beach erosion, particularly to the NSW south coast. Still, as the Office of Environment and Heritage's summary of impacts shows, many coastal regions remain vulnerable to damage following record swells earlier this month. The 17.7-metre maximum wave height recorded on June 6, for instance, surpasses the previous mark by almost three metres.

"If councils consider that they have structures – either public or private – at risk and there is a public safety risk, they should employ a coastal engineer or structural engineer to assess the stability of structures," the OEH has told councils. "The worst coastal erosion impacts occur when there are a series of storms over a short period of time, with no time for beach recovery between events," OEH said in a document obtained by Fairfax Media. It noted that high tides are expected about every fortnight during winter, which if combined with another east coast low, would likely lead to further erosion impacts for coast communities. Hard-hit areas The storm sends waves crashing on the Coogee Surf Life Saving Club. Credit:Peter Rae

A separate OEH survey of the impacts of the early-June monster storm showed that even in regions with limited erosion, most beaches lost considerable amounts of sand. Sydney's northern beaches attracted much of the public's attention as areas such as Collaroy-Narrabeen lost about 50 metres of beach, exposing about 10 homes to risk of collapse. Fairy Bower suffered "oceanic inundation and sand overwash" at its Marine Parade walkway, with "the complete loss" of the public toilets. Mr Gordon, the coastal engineer, said concrete blocks and rocks weighing as much as two tonnes had been shifted in places by the storm's intensity. Around Sydney, other hard-hit areas included the Coogee Surf Life Saving Club, the popular Bondi-Bronte coastal walkway and "significant exposure" of the rock seawall at Cronulla.

Should an east coast low form off the state's south coast, a range of assets and beaches could be vulnerable. The OEH survey noted damage to coastal defences such as the Wollongong Harbour seawall and significant erosion of beaches at Shoalhaven. "Major damage" was also inflicted on infrastructure linked to a wood chip mill at Twofold Bay near Bega, where the jetty and conveyor system was "totally demolished" in sections, leaving an economic impact on the region, the OEH said. Emergency warning The NSW State Emergency Service, meanwhile, has warned people to pay more heed to flood warnings after volunteers were called on to help with 300 flood rescues during the storm earlier this month.

"Floods are extremely dangerous because they can harbour diseases, contaminants, rubbish and fast-flowing undercurrents that can wash people and vehicles away," Greg Newton, acting SES Commissioner, said. "Entering floodwater is the number one cause of death and injury in a flood so everyone should stay out and stay alive." An SES spokeswoman said the service was "taking an interest" in the prospect that another storm will hit the state over the next week but would await confirmation from the bureau before issuing alerts. The SES had 1500 volunteers in the field in the earlier big storm and crews were trained to prepare for back-to-back events, she said. Weatherzone is owned by Fairfax Media, publisher of this website.

* An earlier version of this article incorrectly misspelled Mr Zmijewski's name. Fairfax Media apologies for the error.