Queensland authorities are advising some residents to leave coastal properties in the path of Tropical Cyclone Alfred, amid warnings that a storm surge of up to 1 metre higher than typical tides could inundate communities.

The prime minister, Anthony Albanese, said Australian Defence Force assets have been placed on standby to respond to the looming storm, which was tracking towards the heavily populated coastline between the Sunshine Coast and the Gold Coast.

Alfred was expected to reach landfall early on Friday morning.

Schools will be closed and public transport halted from Thursday as preparations continued and forecasters warned that multiple-day rainfall totals could reach 800mm in some areas, particularly to the south of the centre of the cyclone.

Updated tracking maps on Wednesday morning showed Alfred maintaining its intensity, speed and likely path to landfall.

It was on track to reach the coastline about 1am on Friday somewhere between the Sunshine Coast and Brisbane as a category 2 storm. The model also showed Alfred potentially crossing just south of Brisbane.

Hundreds of Queensland police recruits have begun doorknocking coastal properties that had been identified by local council flood map modelling as being at risk of inundation from a storm surge. Some of these residents will be advised to head to evacuation centres, which were being opened across the south-east.

High tides due in the early hours of Friday are a particular concern for those in waterside communities. Matthew Collopy, a senior forecaster at the Bureau of Meteorology, said Alfred could bring elevated sea levels of between 25cm and 1 metre above the normal highest tides that people see.

“There is some modelling that indicates it may even be slightly higher than that for locations around the South Bay of Redlands and the Gold Coast,” he said.

“[Wind] gusts up to 90km/h … may develop very later today and into early Thursday, increasing to destructive winds up to 130km/h gusts as Alfred approaches the coast.

Daily rainfall totals of between 200mm and 400mm were predicted.

“This could mean the event totals over 800mm,” Collopy said. “This sort of rainfall is expected to produce life-threatening flash and riverine flooding.”

Brisbane’s lord mayor, Adrian Schrinner, said he had been updated on new modelling that showed “20,000 properties across Brisbane could be impacted by storm surge or flooding”.

“These 20,000 properties could experience anything from minor inundation in their yards to significant flooding inside homes.”

Brisbane – a city of 2.5 million people – has been severely flooded three times in 15 years.

Schrinner said the areas “most at risk” were beachside communities – including Nudgee Beach and Brighton – and low-lying suburbs near rivers and creeks, including Windsor, Ashgrove, Morningside and Rocklea.

The Queensland premier, David Crisafulli, said people in evacuation zones should “make a plan and consider your alternate arrangements in the hours of the days ahead”.

“If you are not in one of the zones, if you’re not in storm tide zones or one of the riverine flooding areas, the safest place for you is in your home and that’s the vast majority of Queenslanders.”

Albanese announced subsidies that would mean families with children in childcare would not pay fees if centres were closed in the coming days.

He said the federal government had been assisting with coordination between the New South Wales and Queensland governments.

“There is no Tweed border here,” Albanese said.

“This is not recognised by the cyclone and it certainly should be recognised by government responses.”

There were long queues for sandbags as residents prepared homes for the unusual phenomenon of a tropical cyclone in a large city outside the tropics.

The storm turned back towards the coast, as forecast, on Tuesday afternoon, having moved slowly south from the Coral Sea over about two weeks.

“The current forecast has the system intensifying to a high-end category 2 system prior to landfall on Thursday evening or Friday morning,” the bureau said on Wednesday.

“The possibility of the system reaching a low-end category 3 strength before making landfall cannot be ruled out, but remains a low risk.”

The system was moving about 11km/h as it tracks towards the coast.