North Queensland communities could see not one but two storm surges from Cyclone Debbie because it's moving so slowly, the state's police commissioner says.
The category four tropical cyclone is creeping across the Whitsunday Islands towards Bowen on the mainland.
The Bureau of Meteorology currently expects it to make landfall just south of Bowen between around 2pm AEST.
Police Commissioner Ian Stewart says Debbie is taking its time and fears the cyclone and the storm surge it's generating will span two high tides - the first just before 10am in Bowen and the second 12 hours later.
That's bad news for low-lying communities, where homes could be swamped with sea water.
"With the speed of this cyclone being so slow we're probably now going to go through two tidal cycles, so we'll see a high tide, a low tide and another high tide tonight," Mr Stewart told ABC television.
"And during that time, sadly, that core might still be passing over the coastal areas."
Premier Annastacia Palaszczuk has also warned of a possible second tidal surge and warned Debbie's slow progress means the danger is unlikely to pass on Tuesday.
"This will not pass during the day. For the next 12 hours, I need families to remain safe and remain where they are," she told the ABC.
Low-lying Mackay, where 25,000 homes have been evacuated, is considered particularly at risk from the storm surge.
The Bureau of Meteorology's Queensland meteorologist David Crock said the low tide at Mackay and Laguna Quays were one metre to 1.5 metres above usual levels earlier on Tuesday.
"Given the heights are already well above what they should be, there's likely to be a significant storm surge this afternoon," he said.
He said it was difficult to forecast the exact magnitude of because it depended on a number factors, including wind speed and the shape of the coastline.
Fellow meteorologist Adam Blazak said the storm surge threat could remain after Debbie's eye crossed the coast and could potentially impact coastal areas from Townsville to Mackay.
