Residents in Western Australia’s far north are bracing for dangerous storm surges caused by Cyclone Veronica, while Northern Territory residents are slowly returning home as ex-cyclone Trevor circles back towards Queensland.

Trevor crossed the mainland as a category 4 storm on Sunday morning, producing wind gusts of 230km/h around the NT’s border with Queensland, but shortly after midnight, the storm was downgraded to a tropical low.

The first repatriation flight carrying people back to Angurugu and Umbakumba took off on Sunday morning, and further plans are being made as assessors sweep through properties to see if they are safe.

Ex-tropical #CycloneTrevor weakened to a tropical low at 3.30 am ACST this morning, after crossing the coast as a powerful Cat 4 system. Damaging winds & heavy rain leading to localised flooding are still possible over the next few days. Latest warnings: https://t.co/30lmNQMMcP pic.twitter.com/Jp4fYaNKJL — Bureau of Meteorology, Northern Territory (@BOM_NT) March 24, 2019

Teams have cleared homes in Angurugu, Umbakumba and Ngukurr, but officials are still waiting for word about homes in Borroloola and Robinson River and Bickerton Island, west of Groote Eylandt.

“This does take a personal toll,” the NT chief minister, Michael Gunner, said on Sunday. “Your homes, your lives, the places you know and care about are threatened.”

Communities evacuated to Darwin and Katherine last week were spared a direct hit. More than 2,000 people were evacuated from communities, the largest such effort in the NT since Cyclone Tracy hit Darwin in 1974.

Numbulwar residents in Katherine have been asked to stay at their registered shelter on Sunday night before buses start to take them home on Monday morning.

The storm is expected to come within 100km of Tennant Creek on Sunday afternoon before moving south-east towards the Queensland border in coming days. Areas within 150km of the storm’s centre are expected to receive up to 200mm of rain per day.

The bureau issued a flood watch for the drought-hit Barkly region and rivers around the Carpentaria coast, warning of falls of up to 200mm.

“The black soils [in the Barkly] have been very hard-baked and so we are expecting, with those heavy falls, for rainfall to run off rather than soak in,” bureau forecaster Todd Smith said on Saturday.

“So we can see some localised flash flooding – roads being cut, communities being isolated. It’s really the next few days that’s going to pose a rainfall risk to the Barkly.”

Meanwhile, the powerful, slow-moving Cyclone Veronica is bearing down on the West Australian coast, bringing destructive wind gusts, flooding rain and dangerous tide surges over a prolonged period.

It was downgraded to a category 3 system as it began lashing the coastline of the Pilbara region between Dampier and Port Hedland about 6am on Sunday.

Authorities in the Pilbara have issued a red alert, telling residents between Pardoo and Mardie to take shelter immediately and brace for howling winds and rising tides.

A significant storm surge was predicted for parts of the Pilbara coast, with a high risk that properties in Port Hedland could be inundated, according to WA’s Department of Fire and Emergency Services.

“Tides are at the highest point this weekend, which increases the risk of large storm tides. The surge may be up to four metres on top of the existing tide level,” it warned.

Residents were urged to stay indoors in the strongest and safest part of their homes.

“We’re expecting the potential for a very dangerous storm surge as the tropical cyclone pushes water up against the low-lying coastal areas,” Bureau of Meteorology senior forecaster James Ashley said.

Ashley said Veronica was a slow-moving system that would bring a prolonged period of destructive winds and heavy rain.

“We are expecting a prolonged period – 12 hours or more – of destructive winds near the core of the cyclone. We’re expecting a prolonged period of heavy rainfall so flooding is going to be an issue.”

Western Australia’s fire and emergency services chief superintendent, Paul Carr, praised the community for their response to the cyclone but said it was a significant event.

“We are looking down the barrel of a significant tropical cyclone impact,” Carr said.

People in the Port Hedland area were urged to check storm surge modelling maps and start preparing to relocate to a safer place if affected.

The system was expected to remain a category 4 on Sunday, weakening to a category 2 on Monday.

The last category 4 tropical cyclone to hit the WA coast was Christine in December 2013.

Veronica is the third tropical cyclone this season.