The Bureau of Meteorology has advised Tropical Cyclone Joyce is expected to develop around 140 kilometres west south-west of Cape Leveque, and both Shell's floating LNG vessel Prelude and the Inpex Ichthys Explorer are currently moored near the category three storm at the Browse Basin.
Both vessels are fixed to the sea floor and unable to move; however, accommodation vessels are still attached and are not fixed to the sea floor.
The Maritime Union of Australia confirmed the accommodation vessels could move in the event of extreme weather and, in rare cases, become dangerous.
Around 400 workers are on board the Ichthys Explorer, and said they were advised it was "business as usual" on Thursday morning as work continued through the yellow alert.
The area near the docking point known as "the field" for Inpex has recorded swells up to four metres high and 25km/hr winds on Thursday afternoon, according to the Bureau of Meteorology.
Conditions are expected to worsen as Cyclone Joyce gathers speed, and both Shell and Inpex have braced for impact.
"Shell will continue to monitor weather conditions in the vicinity of our Prelude FLNG operations and enact adverse weather procedures if required," a spokeswoman said.
"Ensuring the safety of our staff and contractors always remains our key priority."
An Inpex spokeswoman said the company had already enacted some of its safety policies.
"Safety is the number one value on the Inpex-operated Ichthys LNG Project," she said.
"We have rigorous cyclone response plans in place at the project facilities in the Kimberley, the Northern Territory and offshore, including down-manning and re-positioning accommodation facilities when required."
The Inpex facility has adjusted its personnel numbers, changed over some of its crew, repositioned the accommodation vessel and de-manned one of its drilling rigs closer to Broome.
But both facilities still sit within 150 nautical miles of the cyclone and could cop the brunt of it.
According to the National Offshore Petroleum Safety and Environmental Management Authority, the companies lodge their own requirements with the authority, which approves or denies them.
"The [existing] regulations do not prescribe how close vessels, offshore rigs or accommodation barges can be to a cyclone or when work should stop in the event of a cyclone," a spokesman said.
"Rather, every operator must identify in their safety case the risks to occupational health and safety specific to their facility and activities - including during cyclonic conditions - and describe the controls that will be in place to reduce those risks to as low as reasonably practicable.
"Risks may vary between facilities, locations and activities and as a result so will the controls to manage those risks. NOPSEMA's inspection regime ensures the controls described in the operator's safety case are maintained."
NOPSEMA said it could not release the specific details of any operator's safety case, but both companies said their vessels are "built to withstand a 10,000-year weather event".
A representative for the maritime union said if it was known workers were in danger from the cyclone, it was not acceptable to leave the accommodation vessels attached at sea.
"If there is any threat to the safety and wellbeing of workers, the workers should be removed from the vessels," he said.
"There are cyclone procedures in place and they need to be adhered to."
De-manning an offshore facility is known to be an expensive measure.
The Australian Mining Workers Union is also monitoring the situation.
"The AMWU is very aware of this, and there are very strict guidelines in place to protect workers in this situation," a spokesman said.
"It is regulated by a federal agency by the name of NOPSEMA. Shell and Inpex have lodged a Cyclone Management Plan with the agency, and we have no reason to believe it is not being adhered to."
As the situation develops, concerned workers have pointed out similarities with Cyclone Quang back in 2015 - a category two, whereas Cyclone Joyce is category three.
Australian Manufacturing Workers' Union state secretary Steve McCartney said the workers had a rough time when Quang hit the rig.
"This company had plenty of warning that this cyclone was coming, yet it left the evacuation until the last minute putting the safety of the workers at risk," he said.