Glenda is lashing the coastline with destructive gales as its eye threatens to cross the coast later this evening just west of the towns of Karratha and Dampier, about 1,540 kilometres north of Perth.
Wind gusts of up to 280 kilometres per hour have been recorded near the centre of the storm.
Bureau of Meteorology senior forecaster Bruce Buckley said Glenda could get stronger before it crosses the coast.
“It could intensify just a touch, and it could briefly reach category five, but it is more likely to cross the coast as a category four,” Mr Buckley said.
He said Glenda is also bigger than Cyclone Tracy, which flattened Darwin in 1974.
“Tracy was an extremely small system, Glenda is a much larger system, affecting a much greater area, and it is a stronger cyclone than Tracy was as well.”
Earlier, major oil and mining operations shut down and residents were told to take immediate shelter as Glenda bore down.
State emergency services in Western Australia issued a “red alert” for people in coastal areas around the massive oil and ore ports of Karratha and Dampier, meaning residents should halt evacuations and take shelter.
“The cyclone is basically very close and there are extreme winds and a lot of danger. If people haven’t evacuated by now, it’s probably too late,” said spokesman Jim Cahill.
The Pilbara is Australia’s main iron ore producing region and the site of major oil and gas fields, with a population of about 10,000.
The northwest Australian coast is known as “cyclone alley” and Glenda is the sixth tropical storm to hit so far this season.
Glenda is expected to create a very dangerous storm tide and flooding in the region, which has already seen substantial rains in recent weeks, the height of the eastern Indian Ocean cyclone season.
Ahead of Glenda, mining and oil giants BHP Billiton, Rio Tinto, Santos and Woodside Petroleum shut down offshore rigs in the path of the storm and closed port operations in and around Karratha.
Woodside and Santos sent floating oil rigs from their big Cossack and Mutineer Exeter oilfields out to sea away from Glenda’s route.
BHP Billiton and Rio Tinto suspended all shipping of iron ore from its
Pilbara mines, but were continuing mining operations.
Glenda is due to hit just 10 days after a top category five cyclone, Larry, caused widespread devastation in the country’s tropical northeast.
Larry destroyed or damaged hundred of homes and wiped out banana and sugar cane crops, leaving a damage bill expected to top A$1 billion. No one was killed.