It could be two direct hits in a row for the South Island's West Coast, as models for Cyclone Gita show the storm moving further south.

That puts it in line to hit the same areas that were battered by Cyclone Fehi two weeks ago. Buller, Westport and Nelson were all badly affected, with evacuations, states of emergency and school closures caused by flooding.

Gita looks set to bring heavy rainfall and violent winds again across a wide swathe of the northern South Island on Tuesday night, followed by heavy rain in the central South Island.

WeatherWatch forecaster Philip Duncan said the worst swells would be from New Plymouth to Hokitika, but Westport could be "clobbered" by the centre of Gita, with dangerous winds and coastal conditions.

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Tropical Cyclone Gita is now a strong Category 2 tropical cyclone as it begins to turn toward New Zealand. While earlier tracking models had Gita aiming for Wellington, Cook Strait and the upper South Island, the latest models show the cyclone making landfall squarely on the South Island.

MetService meteorologist Claire Flynn stressed that, although it will lose its status as a tropical cyclone, Cyclone Gita will still bring severe weather.

"It will maintain storm force winds around the centre of the storm, and possibly reach hurricane force," said Flynn. "New Zealanders need to be aware that, while it will no longer be a tropical cyclone, that does not mean it has weakened or dissipated."

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But forecasters say the storm's final track is still uncertain. It could split when it hits the Southern Alps, ending up twice as wide by Wednesday and spreading its energy over a greater area.

That means parts of New Zealand that were expecting gales could have calm weather, and other areas could get unexpectedly severe weather - so WeatherWatch is warning everyone to keep an eye on forecasts.

Gita is south of New Caledonia right now, with a maximum sustained wind speed of 111km/h, according to WeatherWatch.co.nz. That is likely to weaken to around 90km/h today.

The latest US models show Gita aiming for the South Island, although the Southern Alps could split the storm in two, spreading its energy further afield. Image / WeatherWatch
The latest US models show Gita aiming for the South Island, although the Southern Alps could split the storm in two, spreading its energy further afield. Image / WeatherWatch

WeatherWatch answers some frequently asked questions:

Which areas will be worst affected?

At the moment the West Coast, the Southern Alps (especially the northern half) and the upper South Island. Rain, heavy at times, may also spread into the eastern South Island for 24 hours. The lower and western North Island is also exposed - and as the low morphs into a new system other regions might be impacted.

What is happening today?

Gita should stay a Category 2 tropical cyclone in the Tasman Sea today and start turning more southwards. Today's tracking models are predicting the worst of the storm will move further south than previously thought - although this could change. All of New Zealand is currently at risk of being affected by Cyclone Gita but the worst of the winds will cover an area of 900kms in diameter. This means around half of New Zealand should be on the outside of the worst part.

How far could weather warnings spread?

MetService's Severe Weather Outlook for Saturday indicated central New Zealand and the upper and western South Island were most at risk. Northern New Zealand might see gales but the tracking models don't yet agree on whether this will happen. The next severe weather update is due this afternoon.

Where will the worst wind and rain be?

This storm is expected to split up when it hits the South Island mountains, making it hard to be precise. Current models suggest the worst winds will be in the Southern Alps, West Coast and Cook Strait area. It may also be windy along the North Island's west coast as far north as Auckland and Northland. Rain will be heaviest over the South Island.

Is Gita going to be a repeat of Giselle or Bola?

No two cyclones are the same - they are as unique as human beings. Cyclone Gita is following a similar track to the recent Cyclone Fehi now but is more powerful. Those directly in the path of the storm should be prepared for floods, slips, power cuts, road closures and wind damage. Big seas and damaging waves will also cause coastal flooding and damage directly where the centre of the storm comes in, which still looks to be the north western corner of the South Island on Tuesday night - this could still change.

Video explaining how a cyclone is formed.

How far south will Gita go before losing "tropical cyclone" status?

WeatherWatch's Philip Duncan and Niwa's Ben Noll earlier predicted Gita

(cyclone with a warm core). That's looking less likely, but it will get further south than most tropical cyclones. The status change won't make a difference to wind speeds - these will still probably be low Category 2 status, moving to high Category 1 as it makes landfall. Gusts in the mountains could be much stronger - up to 200km/h.