Models are increasingly suggesting New Zealand could be hit by the remnants of a tropical cyclone currently wreaking havoc in the Pacific.

But MetService has stressed things could change between now and a week's time, when more than half of current models project the system making landfall over the North Island.

Tropical Cyclone Gita, which has already caused considerable damage and flooding in Samoa, has strengthened to a severe category three storm and is set to further intensify as it makes its way across the Pacific.

Satellite image in the visible spectrum from the geostationary MT-SAT taken at 1:00pm NZ Standard Time showng Tropical Cyclone Gita to the North East of New Zealand.
Satellite image in the visible spectrum from the geostationary MT-SAT taken at 1:00pm NZ Standard Time showng Tropical Cyclone Gita to the North East of New Zealand.

It was currently tracking southwest-ward or westward over Tonga from later today and tomorrow.

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Climate scientist Dr Jim Salinger said two of the world's best forecasting models showed what would be an ex-tropical cyclone passing across New Zealand either February 19 or 20.

Graphic from the JTWC issued 11 February 2018 showing the likely track for Tropical Cyclone Gita to 18 February 2018
Graphic from the JTWC issued 11 February 2018 showing the likely track for Tropical Cyclone Gita to 18 February 2018

Both NOAA's Global Forecasting System and the European Centre for Medium Range Forecasting (ECMWF) pointed to a landfall in the Waikato and exiting Hawke's Bay.

The former model indicated the day of action would be Monday, and the latter, Tuesday.

"The ECMWF is usually the better model: one ensemble forecast consists of 51 separate forecasts made by the same computer model, all activated from the same starting time," said Salinger, an honorary research fellow at Otago University.

"The starting conditions for each member of the ensemble are slightly different, and physical parameter values used also differ slightly.

"The differences between these ensemble members tend to grow as the forecasts progress, that is as the forecast lead time increases."

Image / MetService
Image / MetService

Salinger said the Joint Typhoon Warning Centre also showed the cyclone cruising across Tonga then westwards to the north of New Zealand, as did Australian and UK forecasting models.

"The amazing aspect of this tropical cyclone is its path across three countries so far - and a fourth likely with New Zealand."

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Metservice meteorologist Mickey Malivuk said the majority of close to 100 models were showing the system heading toward New Zealand.

"The question is where over New Zealand - it's looking more likely it's going to be over the North Island."

But some models were still indicating the system might just continue rolling further westward.


"We are fairly confident for the next week that it will head westward, crossing Tonga, going just south of Fiji, and then toward New Caledonia - but from then on things diverge a bit with the models."

Malivuk said the system was still evolving and "could go wherever it wants, almost".

WeatherWatch said Gita was now much more powerful than recent Cyclone Fehi, which smashed a large swathe of the country last week, flooding homes and businesses, stranding travellers when damaged roads were closed and causing dramatic storm surges.

Multiple reliable models suggested that Gita would track further southward towards the New Zealand area around next weekend or early the following week, the company stated.

"It's still far too early to know if it will directly impact New Zealand - it remains one to watch and WeatherWatch.co.nz hopes to have more specific details this Monday about whether or not this will be something for New Zealanders to seriously focus on."