The worst of Cyclone Donna was expected to bypass New Zealand, WeatherWatch.co.nz said, with the eye of the storm likely to follow a southward path east of East Cape.
The Vanuatu Meteorology and Geo-Hazards Department said Donna was about 245km west-northwest of Torres and 365km west-northwest of Vanua Lava at 5am local time (6am NZ time).
"Winds close to the centre are estimated at 145km/h, gusting to 205km/h."
Destructive winds of 90km/h gusting to 130km/h and "very rough to phenomenal seas with heavy swells" were expected to continue in the Torba area and parts of the Sanma province, the meteorological department warned.
"Heavy rainfall and flash flooding is also expected over Torba, Sanma, Penama and Malampa provinces especially over low lying areas and areas close to river banks."
Owners of coastal properties in Vanuatu told WeatherWatch.co.nz on Thursday that they'd already started battening down the hatches in preparation for the storm.
Red Cross and World Vision volunteers are on the ground in Vanuatu and ready to help those affected when they need assistance.
World Vision Vanuatu country director Mike Wolfe told NZME since Cyclone Pam, staff had been working with communities on "how they're going to be prepared for disaster, and what they're going to do in times of disaster".
"We're really concerned about children and families being more vulnerable due to impacts to drinking water and shelter," he said.
Wind speeds are likely to increase to 210km/h, with gusts of up to 260km/h later today and tomorrow expected before slowly dying down later in the week.
The exact path of the storm is unclear, WeatherWatch.co.nz said, because "the South Pacific islands is possibly the trickiest place on earth" to track a storm's path.
"Cyclones in this area tend to meander a lot and cross back on themselves in the same unpredictable way a coin, once spun on a table top, can move around with a mind of its own.
"Tracking a cyclone around small islands is very hard - almost like hitting a hole in one when playing golf. When it's a larger nation like Australia or the USA then the storm has an enormously greater chance of hitting land."
However as the storm had moved further west, Noumea in New Caledonia was now more at risk of a direct hit, WeatherWatch.co.nz said.
A low from the Tasman Sea was expected to bring Donna's rainy remnants along with it when it sweeps across the country overnight on Sunday.
However it was uncertain at this stage whether the tail of the storm would bringing rain heavy enough to trigger severe weather warnings or just patchy falls, WeatherWatch.co.nz said.
