Cyclone Gabrielle is expected to strengthen to category three as it barrels toward Norfolk Island, in line to pummel New Zealand's North Island.
The system is predicted to intensify to category three on Friday morning, picking up speed and strength with 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.
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.
The cyclonic threats come less than two weeks after Auckland was hit by historic levels of rain, which killed four people and caused widespread flooding and landslides.
