Cyclone Gabrielle continues to strengthen in the Coral Sea as it barrels toward Norfolk Island, remaining on track for a direct hit on New Zealand's North Island.
Forecasts warn Gabrielle continues to gather strength and could potentially be "the most serious storm to impact New Zealand this century".
The system remained a category two on Thursday and sat northeast of Mackay, slowly tracking southeast about 15km/h.
It is expected to intensify into a category three on Friday, packing winds of between 165km/h and 224km/h, the Bureau of Meteorology says.
The system's trajectory has shifted and is in line to make landfall on Norfolk Island late on Saturday or early Sunday.
Norfolk residents are bracing for gusts of up to 140km/h, heavy rain and abnormally high tides and large waves.
"Tropical cyclone Gabrielle is expected to intensify and move onto a track towards the southeast with increasing speed in the next day or two - this is very likely to bring the cyclone near or over Norfolk Island during Saturday and Sunday," a BOM alert says.
Emergency services on Norfolk Island have activated their cyclone response plan as Gabrielle closes in.
"The community is advised to familiarise themselves with the alert levels and consider what action they will take if the cyclone threat is continuing," the island's emergency management team said.
The storm is expected to continue to track southeast out of the tropics at the weekend, and is predicted to reach New Zealand between Sunday and Tuesday.
"No official warnings are yet locked in this far in advance, the data this morning means the likelihood of severe weather across much of the North Island looks highly likely," WeatherWatch.co.nz said on Thursday.
"If this current modelling comes true, this will likely be the most serious storm to impact New Zealand this century, especially with Auckland being in the mix for a potential direct hit."
Heavy rain and gale-force winds are also expected to lash the upper South Island.
"Just as Gabrielle reaches northern NZ it's expected to encounter higher air pressure to our east - this acts like an invisible brick wall in the sky and that is expected to then curve the cyclone due-south and directly into the upper North Island" says WeatherWatch.co.nz head forecaster Philip Duncan.
"This is an extremely concerning set-up and all North Islanders - and some in the South Island - need to be well aware of this storm's path and potential severe weather.
"Not only has the modelling been very consistent in the past 48 hours, but the angle this storm is tracking in from already means northern NZ would naturally be at a higher risk."
The warnings come less than two weeks after Auckland was hit by historic levels of rain, which killed four people and caused widespread flooding and landslides.
