Tropical Cyclone Penny ramped up to a category two system overnight, but the Bureau of Meteorology (BOM) says the system is slowing to a temporary halt and is expected to weaken when it eventually approaches the Queensland coast.

At 10:00am on Friday, the BOM radar placed the system 620 kilometres east of Willis Island and 1,020km east north-east of Townsville.

BOM meteorologist Michael Knepp said the system was expected to become almost stationary over the next 24 hours before turning west towards the coast.

"As it starts moving to the west, we expect the system to start to weaken to a category one system on Sunday, and then more than likely an ex-tropical cyclone on Monday or Tuesday," he said.

"Even though we are forecasting the system will become an ex-tropical cyclone, there is still the possibility it will maintain cyclone strength as it nears the Queensland coast."

Impacts possible anywhere north from Fraser Island

Mr Knepp said there was still uncertainty about the system's movements.

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"Anywhere north of Fraser Island towards Cooktown, anywhere along that coastline could be impacted by this system," he said.

"Because those steering mechanisms have weakened, it's starting to move slower and [the movement of the system] will be quite unpredictable … over the weekend."

It has been less than a month since ex-Tropical Cyclone Owen dumped record-breaking rain on parts of north Queensland, including 681 millimetres in 24 hours at Halifax, north of Townsville.

Mr Knepp said Cyclone Penny could also bring heavy rainfall and strong winds to parts of the coast.

"Owen was an ex-tropical cyclone as it moved through the Halifax area — it produced prodigious amounts of rainfall and it even produced some gusts," he said.

"If [Penny] does weaken into an ex-tropical cyclone, probably the main impact will be the rainfall, especially if the system starts to move slower — but we will still see some wind with it."