Australia Weather News

Forecasters say a severe tropical cyclone set to curve around the WA coast towards Perth is the strongest of the season, but have assured the public there is no cause for alarm.

Tropical Cyclone Marcus has strengthened into a category five system 950 kilometres northwest of Port Hedland and is tracking west, well away from the WA mainland.

It now has the strongest category rating possible for a cyclone and is generating winds of 205 kilometres per hour, with gusts of up to 285kph.

It is expected to remain at that level or possibly strengthen even furtheruntil Thursday, when it should start weakening and moving south along the coast. It is then expected to turn east towards Perth on the weekend.

The cyclone has already battered Darwin, passing over the Northern Territory capital as a category two system on the weekend and causing widespread damage.

Echoes of Cyclone Alby

The forecast track map for Marcus is remarkably similar to the path Cyclone Alby took before it caused widespread damage to WA's south-west in 1978, killing five people.

But the Bureau of Meteorology's Bradley Santos said Marcus is expected to behave entirely differently.

"Cyclone Alby had a specific set of circumstances that caused it to act the way it did," he said.

"There was a significant cold front out to the west, which aided the system being accelerated towards the south-east."

He said forecasts for next week show the conditions should create an unfavourable environment for Marcus to behave in the same way.

"If you look at the charts, there's a high-pressure system that will be cradling the [cyclone] system," he said.

"And what's going to happen here — is as it makes that curve it will encounter cooler sea-surface temperatures and strong upper-level winds will sheer the top of the system off.

"What's left of Marcus might produce some rain and windy conditions over the South West, but we're not expecting anything more severe."

"It is a hazard to aviation and shipping in the area, of course, but in terms of impacting a WA community, that threat has now passed."

Strongest cyclone of the season

Mr Santos stressed there was still a lot of uncertainty so far out from next week, but said the Bureau of Meteorology used the best technology available to create its tracking maps.

"We look at computer models guides from around the globe, assess their strengths and weaknesses and combine them in a meaningful way," he said.

Mr Santos said while the system was not expected to cause any issues for WA, it has been interesting to watch from a meteorological perspective.

"When cyclones are quite weak, it's quite difficult to know where there centre is, using the conventional tools that we have," he said.

"But right now the system's got a well-defined eye and quite a good structure."

Tropical Cyclone Marcus is the strongest system in WA's area of responsibility since Tropical Cyclone Ernie last year.

Ernie developed in the early part of April last season before it spectacularly developed into a category five over the space of about 30 hours.

Ernie remained over the ocean and weakened into a tropical low well offshore from the WA coast.