The weather bureau has issued a cyclone watch alert for the Top End of the Northern Territory.
A watch was declared at 5pm (CST) for coastal areas stretching from Dundee Beach to Nhulunbuy, including the Tiwi Islands and Darwin.
The bureau says gale force winds could develop in the next 48 hours.
Senior Forecaster Andrew Tupper says a monsoon trough is developing about 300 kilometres north-north-east of Darwin in the Arafura Sea.
“It is virtually certain that that low is going to stay out over water,” he said.
“When it stays out over water, that is a very favourable environment for cyclone formation.
“What is not certain is where it will go after that.
“It is likely, very likely that a cyclone will form but we do not know if it will go west or east or south.”
Meanwhile, the Northern Territory Airports group says it has a committee preparing to deal with passengers who may have their Christmas travel plans disrupted by the possible cyclone.
Darwin airport director of services Jim Parashos says if some flights have to be cancelled there are not a lot of free places on other planes.
He says many flights out of Darwin are already booked at 85 per cent capacity, but there is not a stampede to get out of the city.
The heavy bookings are mostly connected to Christmas travel.
“We will work with our airline customers as the weather develops to assess what we will do going forward,” he said.
“There are not many seats available, so it is not that straightforward.
“I think most of the locals have been through this before, so I think they will take a wait-and-see approach.”
The weather bureau says it is trying to better prepare people for a possible cyclone than they were for Cyclone Carlos in February.
Cyclone Carlos quickly formed over Darwin and there was confusion among many government workers about whether they should immediately go home or stay at work.
In the ensuing storm, more than 400 millimetres of rain fell on the city overnight and houses were flooded.
Trees and powerlines were brought down and emergency services crews received more than 2,000 calls for help.
Forecaster Angeline Prasad says people should be taking precautions well in advance of the threatening weather this time.
“We are trying not to have a repeat of the Carlos situation, which is why we have let the public know quite early on that there is potential for a cyclone by the end of the week,” she said.
NT Emergency Services director Peter Davies says people in the Top End should not wait for a cyclone watch to be declared to get prepared.
“If a cyclone watch is declared, the stores empty,” he said.
“So if you haven’t got your three days’ worth of stuff to look after yourself in a cyclone then you really need to go and get it now.”
Jane Bardon and Myles Morgan