The cyclone is expected to weaken even further and turn slowly to the north west.
Earlier, gale force winds and huge waves caused disruptions to flights.
The severe weather also battered a cargo ship, which lost 32 large containers of the potentially dangerous chemical ammonium nitrate.
Queensland maritime authorities say they are assessing the risk from the spilt chemicals.
Brisbane Airport has been monitoring winds generated by the storm system.
Two Virgin Blue flights from Sydney and Melbourne bound for the Sunshine Coast will be diverted to Brisbane today due to high winds.
Airport spokesman Jim Carden says Brisbane's runways will remain open.
"[The airport has] proven over many years to be able to operate in very high wind conditions," said Mr Carden.
The Port of Brisbane has activated its contingency plan.
Regional Harbourmaster Glenn Hale says extra tug boats have been called in and ships are being secured.
"Arrangements are being put in place for extra moorings on the larger vessels," said Mr Hale.
At least 10 small boats have broken free from moorings in the Brisbane River and Moreton Bay, he said.
- Australian Broadcasting Corporation
- © ABC