The last confirmed sighting of the 52-year-old was at Quayle Street, St Helens on November 28.

Mr Norrish has an acquired brain injury. 

He lives at St Helens, but is known to frequent Launceston and Devonport.

On Thursday, the Westpac Rescue Helicopter searched a number of areas at St Helens where Mr Norrish had been previously seen. 

State Emergency Service crews and search and rescue members will begin ground searches in and around the St Helens area over coming days, police said. 

Mr Norrish is described as being about 174cm tall, slim build, fair complexion and with a long and pointed brown beard.

He was last seen in the St Helens area wearing cream cargo style pants, a dark coloured zip up jacket and black Blundstone boots.

Mr Norrish walks with a pronounced limp and is known to ride a red mountain bike. 

Tasmania Police Acting Inspector Ben Kromkamp said there had been numerous possible sightings of Mr Norrish and each was followed up. 

“Locating Mr Norrish remains a priority investigation for Tasmania Police and we would like to thank the public for their assistance so far,” Acting Inspector Kromkamp said.

Anyone with information about Mr Norrish’s whereabouts is asked to call police on 131 444, or anonymously through Crime Stoppers on 1800 333 000.