Tonga's northern island groups of Vava'u and Ha'apai are preparing for the arrival of hurricane-force winds with disaster agencies on standby for a response to Severe Tropical Cyclone Ian.
In the from the coordinating Fiji Meteorological Service at 6pm local time (4pm AEDT, 0500 UTC) Ian has again risen to a Category 4 system situated about 170 kilometres northwest of Vava'u and 250 kilometres north-northwest of Ha'apai, moving southeast at about 10 kilometres an hour.
Winds at its centre average nearly 170 kilometres per hour with gusts of up to 230kph.
On its , Ian is expected to be located around 65km west of Vava'u and 140km north of Ha'apai at 4am Tongan local time.
Acting director of the Fiji Met Service Aminiasi Tuidraki says the slow moving cyclone is now expected to reach Vava'u on Saturday morning local time, with very destructive winds beginning several hours before it passes overhead or nearby.
Ian has brushed below Niuafo'ou, Tonga's most northerly island in the Niua group, where gale warnings have been cancelled.
The capital, Nuku'alofa, is not directly in Ian's path but may experience heavy rains and possible flooding.
The Director of Tonga's National Emergency Management Office, Leveni Aho, says residents of the northern islands should prepare for the worst.
"The potential and the threat now lies in the islands of Vava'u and Ha'apai in the next 12 to 24 hours," he said.
Mr Aho is urging affected residents to make sure they are well prepared.
"A reminder to people to make sure that they have enough supplies for the next 72 hours in terms of water, drinking water, and food and (ensure) some basic necessities like radios and mobile phones are charged to maintain communication," he said.
"Make sure that they are in a safe place, if ever the winds arrive keeping away from low lying areas and the coastal areas, make sure that they are in a safe house, sheltered."
The Pacific office of the UN Office for the Coordination of Humanitarian Affairs says Tonga's National Emergency Operations Committee met Thursday to discuss preparedness activities.
The Tongan Red Cross Society has emergency response teams on standby and can access pre-positioned non-food items across five islands.
The New Zealand government has additional personnel at the High Commission to support assessment and response planning.
Military assets are also available for reconnaissance and logistical support if required.
The UN says many people are boarding up windows and have cut leaves from fruit-bearing trees to reduce crop damage.
Kjelll Stayv owns a small hotel in Vava'u and told Radio Australia's on Thursday there is an eerie feeling in the air.
"The sky is milky and grey so there is definitely something coming," he said.
He says preparations for the cyclone are underway.
"On our island and the small outer islands here, there are between 10,000 to 12,000 people," he said.
"And right now there are now many tourists, maybe 100.
"It is a little weird because we have to board up their windows, but they don't have much choice I'm afraid."
© ABC 2014
22:57 EDT In an emergency, would you hand your child over to a stranger you met at a barbecue? #introduction Introduction There once was a mother who gave her baby to a stranger.