Cyclone Gabrielle is expected to reach its closest point to Auckland within hours, and has already brought gale-force winds and drenching rain to New Zealand’s upper North Island, cutting power to almost 60,000 homes and prompting evacuations.

MetService says the position and intensity of the weather system poses a “very high risk” of extreme, impactful, and unprecedented weather over many regions of the North Island through to Tuesday. Residents in the nation's largest city have been told to stockpile up to three days' worth of supplies.

“Impacts are already being felt across northern parts of the North Island and are expected to spread south across the rest of the North Island through to northern parts of the South Island on Monday and Tuesday,” MetService said.

Since noon local time, gusts of up to 160 km/h and rain rates of 30mm in a single hour were recorded. Auckland residents have been warned to expect up to 200mm of rain.

“This rain is expected to cause dangerous river conditions and significant flooding. Slips and floodwaters are likely to disrupt travel, making some roads impassable and possibly isolating communities,” MetService said. For Northland, winds are expected to produce widespread damage and “could lift roofs”.

States of emergency have been declared in Auckland, Northland, Coromandel, Gisborne and Ōpōtiki. Trains have been cancelled, schools are closed and flights grounded, while evacuations were underway in the Whangārei CBD and Town Basin area and some houses were beginning to flood.

People located in low-lying areas close to the rivers were encouraged to self-evacuate because of a high risk of tidal flooding.

The cyclone follows unprecedented flooding in Auckland and surrounds in recent weeks which Suncorp said today resulted in 11,500 claims so far across its Vero and AA Insurance brands.

Group CEO Steve Johnston says around 100 specialists from Australia were dedicated to the New Zealand event recovery efforts, including a team of claims specialists and assessors sent to Auckland to help manage the fallout.

“Given the scale of the flooding event and the follow up rain and cyclonic winds, all available Suncorp Group resources will be deployed to speed up the claims process,” Mr Johnston said. “Our thoughts are with all of our customers experiencing further adverse weather.”

Suncorp says its robust reinsurance program provides additional protection for New Zealand, capping losses from the Auckland flooding event at NZ$50 million ($45.58 million), net of reinsurance cover, and ensuring the retained cost of any potential second declared event in New Zealand is NZ$25 million ($22.79 million).

IAG has previously said its gross costs from the Auckland floods that began January 27 could pass $350 million, and Tower expects to trigger a reinsurance excess of around $11 million and a need to secure new catastrophe cover.

New Zealand’s extreme weather insured losses – which don’t include earthquake – were around $NZ350 million ($319 million) last year, which was a record. Some analysts estimate losses from the recent Auckland flood could come to almost triple that figure.