Australia's eighth cyclone of the season is likely to form in the Gulf of Carpentaria on Wednesday, forecasters say.

A strong low pressure system is near Nhulunbuy, in the western gulf, and moving east.

Bureau of Meteorology forecaster Jonty Hall says there's a moderate chance it will form into a cyclone on Wednesday.

The storm, which would be called cyclone Tim, will then move east over Cape York Peninsula before "popping out" over the Coral Sea.

But it's likely to spare heavily populated parts of the east coast, as Cyclone Sandra did, and move out to sea.

Sandra, currently a 600km-wide, category four cyclone, is approaching New Caledonia and is expected to lash the northwest point of the main island on Wednesday before bringing destructive winds to the capital, Noumea.

It will then head southeast but it could still affect Australian territory.

Mr Hall says Sandra will pass to the west of Norfolk Island on Thursday and bring strong winds and heavy rain.

"It could definitely give them a bit of a blow," he told AAP.

"But the islanders are no strangers to that sort of thing."

The Bureau of Meteorology couldn't confirm reports a ninth cyclone would follow expected cyclone Tim, but would not rule out more cyclones this season.

"We've seen cyclones just before Anzac day," Mr Hall said.

"So there's still another month and a half to wait and see."