GALE FORCE winds and rainfall totals up to 400mm may make a dangerous combination for the Sunshine Coast in the wake of Cyclone Debbie finally reaching land.
Forecasters say gale force winds (63-87kmh) over land were extremely rare but remained a possibility for the Sunshine Coast through Thursday and Friday.
A storm surge of up to half a metre may also cause coastal inundation of low-lying areas overnight Thursday when a 1.93m high tide is expected at 10.04pm.
The Sunshine Coast Local Disaster Management Group (LDMG) has urged the community to be prepared for heavy rainfall, strong winds and possible flash flooding.
Between 200-400mm of rain was possible in hinterland areas over a 24-hour period.
The Mary River catchment was expected to receive significant rainfall. Dangerous surf conditions and beach erosion were also expected.
The Category 4 Cyclone Debbie smashed into the North Queensland coast at just after noon today.
Winds to 265kmh buffeted coastal towns from Bowen to Mackay with Hamilton Island copping a hammering as residents and guests hunkered down to ride out the cyclone.
Rainfall of up to 135mm in 3.5 hours have been experienced in some places.
- The latest videos of Cyclone Debbie
- Hamilton Island a mess after hit by 263km/h winds
- Cyclone Debbie: More than 20,000 homes without power
- Pioneer River over the bridge in Mackay
Cyclone Debbie's size will ensure it maintains as a Category 2 cyclone until at least 1am Wednesday before decaying into a rain-laden low pressure system.
Bureau of Meteorology forecaster Adam Blazak warned great uncertainty existed about what's to come.
Modelling is attempting to time both the southward movement of the low pressure system and the arrival of a cold air mass from the south.
The post landfall track of the cyclone has shifted continuously in recent days first modelled to go back to sea off the Sunshine Coast and then further south into NSW.
Latest models show it tracking between Brisbane and the Sunshine Coast.
Where the tropical low pressure system that was Cyclone Debbie and the cold air mass interact will produce very heavy rainfall.
Mr Blazak said an hour's difference in the timing of either system could result, for example, in whether an extreme rainfall event occurred over Caloundra or Double Island Point.
"There's a reasonable confidence (ex-Cyclone Debbie) will take a sharp left turn towards south east Queensland," he said.
"It's a question of timing."
Modelling has struggled all week, Mr Blazak said, to settle on a defined path for the two variable events.
He said what was certain was that the south east corner will experience widespread rain in the order of 40-50mm for the rest of this week.
Much greater rainfall however was expected at the point of interaction between the two weather systems.
Mr Blazak said people living in south east Queensland should continue to monitor the bureau's forecasts because the situation could change quickly.
The Local Disaster Management Group has moved to 'alert' status in preparation for what's to come.
Co-ordinator Andrew Ryan said Tropical Cyclone Debbie would be downgraded to a rain depression and continue to track south.
"It's also likely there will be a storm surge of 500mm, with localised tidal inundation possible on Thursday night," Mr Ryan said.
"We expect road conditions to be hazardous, with water over local low lying roads, and tree and vegetation damage, so please stay off the roads if you can.
"If travel is unavoidable, remember to never drive through flood waters."
Mr Ryan urged residents to prepare a household emergency kit and a plan to help themselves, their families and neighbours.
"There's a possibility of isolation for some hinterland areas, so please do make sure you have enough food for up to three days," he said.
"Don't be complacent while the weather looks fine here - take advantage of the days we have to prepare and secure loose outdoor items now."
Visit council's Disaster Hub at www.disaster.sunshinecoast.qld.gov.au for all the information you need to be prepared before, during and after severe weather including how to plan an emergency kit, weather warnings, road closures, airport information and news updates.
For life threatening emergencies call 000
Emergency help in storms and floods SES 132 500
Update your news preferences and get the latest news delivered to your inbox.