The ADF has sent a C-130 Hercules transport aircraft to help search for fishing trawler the MBC, which was last heard from yesterday morning when the crew activated their emergency beacon.

Three men are on board the trawler in very rough seas about 140 nautical miles east of Rockhampton, Australian Maritime Safety Authority spokeswoman Tracey Jiggins said.

But tropical cyclone Hamish was expected to weaken further today and move away from the search area, Ms Jiggins said.

"The weather's a bit better than it was yesterday," she said.

"It's still very stormy, there's some cloud cover and very strong winds but the cyclone itself is about 120km away from the search area today and it's continuing to move further away.

The Hercules had joined AMSA's search and rescue Dornier aircraft in the air today and three helicopters were on standby for a rescue run.

"We've also diverted a merchant vessel into the area, it's still several hours away from the location, it should be there about lunchtime," Ms Jiggins said.

At 4am today cyclone Hamish was estimated to be 290km east of Gladstone and 140km northeast of Sandy Cape, moving south southeast at 11kmh.

Currently a category four severe tropical cyclone, Hamish is predicted to make a turn for the coast somewhere between Yeppoon and Tewantin on Wednesday.

However, forecasters say it is still too far out to predict whether it will make the coastline.

The Bureau of Meteorology predicts Hamish may be downgraded to a category two cyclone by Wednesday afternoon.

BoM forecaster Gavin Holcombe said the cyclone was in the process of becoming a category three cyclone on Tuesday morning.

However, winds of up to 250kmh were recorded near the cyclone's centre at 4am (AEST).

The BoM says damaging winds are expected to continue to affect the northern part of Fraser Island during the next 24 hours.

People on the northern part of Fraser Island are being advised to stay calm and remain in a secure shelter while the damaging winds continue.

The BoM says people on the mainland coast between Yeppoon and Tewantin should consider what action they will need to take if the cyclone threat increases.