Two Tropical Cyclones Target Australia
© The Weather Channel
Two Tropical Cyclones Target Australia
Two powerful tropical cyclones are about to smash Australia. One system, a Category 4, has already forced the largest evacuation in NT history.

Cyclone Trevor is barrelling towards the Northern Territory as it intensifies into a destructive system and causes monster waves predicted to wreak havoc on communities in its path.

At the same time, Cyclone Veronica is strengthening as it steams in from the west to "severely impact" the Pilbara region.

The two storms converging on Australia's north and west coasts have sent social media into a frenzy. Meteorologists have dubbed them "double trouble" and the graphics are frightening.

Trevor is brewing in the Gulf of Carpentaria and is expected to develop into a Category 4 system as it approaches the coast.

Bureau of Meteorology forecaster Todd Smith said the cyclone could strengthen to a Category 5 with winds of more than 300km/h.

Even as a much smaller and weaker storm in the Coral Sea, Trevor generated four-metre waves. According to experts, it's likely to create much larger waves and a significant storm surge the second time around, when it makes landfall on Saturday.

BOM's latest advice is that the system will continue to intensify in the Gulf of Carpentaria. "A severe impact on the southwestern Gulf of Carpentaria coast is likely over the weekend," the bureau said.

A flood watch was issued for the Carpentaria Coastal Rivers and Barkly regions with predicted rainfalls of 150-250mm on Saturday and isolated falls to 300mm along the coast on dry ground following a poor wet season.

The imminent arrival of the storm has reportedly forced the largest ever evacuation for communities in the NT ahead of a cyclone.

More than 1000 residents have been evacuated from Groote Eylandt and Numbulwar with another 1000 people being moved out of Borroloola, the McArthur River zinc mine, Robinson River and other communities all along the Gulf of Carpentaria coast to Queensland.

The severity and threat of the storm, as well as complications with the remoteness of the area, led to the decision to evacuate, Chief Minister Michael Gunner said on Thursday.

A state of emergency has been declared in the Gulf country, with schools closed and police can order people to evacuate and close roads and businesses.

It's the largest evacuation prior to a cyclone in the territory's history and largest type of any evacuation since Cyclone Tracy.

The entire NT Gulf coast is on flood watch with gale-force winds, heavy rain and storm surges extending 300km from the eye of the cyclone.

"As Cyclone Trevor tracks across the Gulf of Carpentaria, the Bureau of Meteorology is forecasting that the cyclone will make landfall between Borroloola and Groote Eylandt during Saturday as a category four severe tropical cyclone," he told reporters.

"Marine conditions in the gulf are deteriorating from (yesterday) morning."

Evacuees from Groote Eylandt after flying to Darwin ahead of Cyclone Trevor
© Glenn Campbell/News Corp Australia
Evacuees from Groote Eylandt after flying to Darwin ahead of Cyclone Trevor hitting the NT Gulf Coast.
Very destructive winds, with gusts to 260km/h, heavy rainfall and a dangerous storm tide are expected near the cyclone centre as it approaches and crosses the coast, Mr Smith said.

Rainfall totals of 100mm to 200mm per day will hit ground "hard-baked" by the drought in recent months, meaning likely flash flooding that will affect pastoralists.

Mr Smith has not ruled out the storm strengthening to a category five with winds of more than 300km/h.

The last time a cyclone this strong hit the Territory was Cyclone Lam in 2015 but Trevor is far bigger, according to Mr Smith.

Australian Defence Force Hercules' aircraft are being used to transport people, who have begun arriving in Darwin and Katherine where indoor sleeping facilities are being set up at local showgrounds.

That includes creating barriers to ensure indigenous cultural protocols are followed and people are spoken to in local languages.

"We've used buses, vehicles, ferries, planes, helicopters and anything else in between we can get out hands on," police regional controller Travis Wurst said.

About 600 out of Groote Eylandt's population of 2800 have been evacuated but authorities are now focusing on Borroloola, with a population of 900. The evacuations are starting with the most vulnerable and people who are not evacuated in time will be moved into emergency shelters.

"We have the capacity and capability to look after them as long as we need to, until water and power are safe again and houses are habitable again," Mr Gunner said.

Trevor left behind trail of destruction in Queensland's Cape York Peninsula earlier this week, uprooting trees, caused flooding and roof damage, closed schools and roads and downed power lines.

Trevor lashed the Aurukun community on Wednesday and some 180 homes remained without power on Thursday as residents began cleaning up.

Cyclone Veronica is picking up speed as it progresses towards Western Australia's Pilbara region, where it is expected to hit this weekend.

Veronica is estimated to be 385 kilometres northwest of Port Hedland and is moving southwest at 9km/h.

Gales with gusts to 100km/h may develop between Pardoo and Mardie on Friday evening, and may extend farther east to Wallal and adjacent inland areas later on Saturday.

Destructive winds with gusts exceeding 125km/h are forecast to develop along the coast between Dampier and Pardoo later on Saturday.

A Blue Alert is in place for people in or near communities between Mardie and Wallal, including Port Hedland, South Hedland, Wickham, Roebourne, Point Samson, Karratha, Dampier Barrow Island, Pannawonica and Marble Bar. The Pilbara Ports Authority has begun cyclone preparations across the ports of Ashburton, Dampier and Port Hedland, with anchorages and berths being cleared in a staged manner.

The last category four tropical cyclone to impact the WA coast was Christine in December 2013.

Veronica is the third tropical cyclone for the season.