Tropical Cyclone Hola has rapidly intensified to a Category 4 and could reach Category 5 tomorrow, with winds up to 300km/h as it batters Vanuatu, then heads for New Zealand.
The Fiji MetService upgraded the cyclone to Category 4 this morning, warning of sustained winds of 170km/h. Wind speed is expected to reach 200km/h today.
Vanuatu's Meteorology and Geo-hazards Department said this morning hurricane-force winds gusting to 185km/h were expected to hit Malekula and the Shepherds group tonight and in the next 12 to 24 hours. Damaging gale-force winds continue to affect the island of Ambrym in the Malampa Province.
The system is moving slowly southwest.
Three forecasting models for Tropical Cyclone Hola predict the storm is likely to hit New Zealand's North Island early next week.
Two models, from the UK Met Office, show Hola could hit the Bay of Plenty on Monday. It would be the third cyclone this season to affect New Zealand.
The third model, from the European Centre for Medium-Range Weather Forecasts, predicts it could make landfall about 6pm on Monday.
MetService New Zealand lead meteorologist Mark Todd said computer models were still struggling to give an accurate track but it was looking increasingly likely the storm would affect New Zealand.
Hola has been moving slowly over Vanuatu during the past 24 hours, and reports say gale-force winds are collapsing some houses.
The roof of a classroom was blown off and some houses collapsed on Ambrym as the cyclone arrived, Radio New Zealand reported.
Todd said it was west of Vanuatu this morning, and moving slowly further west.
"We expect over the next day it should start to recurve to the south/southeast, in the general direction of New Zealand.
"If we are lucky it will pass just to the north of us. If we are unlucky, it could be a direct hit into the North Island.
"By then it will become an extra-tropical system, as always happens, but if it does make a direct hit there will be heavy rain and high winds."
A "cut-off low" west of New Zealand has been wreaking havoc as it moves slowly over the North Island.
"We have a deep low in the upper atmosphere and a deep low at the surface generating all the rain and wind," Todd said.
Heavy rain and thunderstorms rocked much of the island last night when up to 200mm falling in places.
Wairarapa, Tararua and Hawke's Bay south of Hastings have a severe rain warning in place through to 9pm.
Heavy rain warnings remain in place for Taranaki through to 1pm.
"The heaviest falls were in the central areas, from Hawke's Bay and the Wairarapa through the central high country to Taranaki," Todd said.
More than 200mm was recorded on Mt Taranaki, and 129mm in nearby Stratford during the past 24 hours.
On the East Coast 90mm fell at Castlepoint in the Wairarapa and 83mm in Taumarunui.
The lower North Island including Wellington has been experiencing gale-force winds.
"These are not expected to ease off," Todd said.
"There will be a gradual trend off, as the weather system moves very slowly.
"There is a risk of more widespread thunderstorms today, mainly in the central and upper North Island, even some hail."
Temperatures today would be much the same as yesterday, and the South Island is "the place to be", Todd said.
"There is a somewhat cooler air mass over the South Island, but it is going to be sunny, with very little rain."
Showers, some heavy with possible thunderstorms. Southeasterly developing. 23C high, 17C overnight.
Auckland Fine spells and occasional showers, possibly heavy with thunderstorms. Northeasterly turning southeast. 23C high, 17C overnight.
Hamilton Occasional showers, possibly heavy with thunderstorms from afternoon. Southeasterlies. 25C high, 14C overnight.
Tauranga Fine spells and occasional showers, possibly heavy with thunderstorms from afternoon. Light winds. 24C high, 17C overnight.
New Plymouth Rain, easing to showers by afternoon. Possible thunderstorms until evening. Strong gusty southeasterly. 21C high, 14C overnight.
Napier Rain, heavy at times. Possible thunderstorms from afternoon. Southeasterlies. 23C high,
Wellington Occasional rain. Strong southerlies. 17C high, 13C overnight.
Nelson Cloudy. Gusty southerlies. 22C high, 11C overnight.
Christchurch Some morning cloud then fine, but chance shower. Cloud increasing evening. Southeast breezes developing. 18C high, 12C overnight.
Dunedin Morning and evening cloud, afternoon fine spells. Southwest developing afternoon. 17C high, 11C overnight.