Cyclone Gita: MetService warns 'it's best to prepare'

MetService is urging people to prepare for Cyclone Gita as it makes its way to New Zealand.

Risk areas are yet to be identified- they will be earmarked closer to Gita's arrival - but MetService says the tropical cyclone is likely to bring with it "highly impactful severe weather".

Gita is expected to approach from the northwest early next week but there is uncertainty as to its speed and track.

There was high confidence of severe gales and heavy rain spreading across central and northern New Zealand by Tuesday and Wednesday, MetService said.

#TCGita blog for the 16th Feb 2018 is available at https://t.co/B54Jqm0BU8
Best to prepare if you are in the risk area. These areas will be refined closer to the event. https://t.co/ePtVj8cXwp Be safe! ^Lisa pic.twitter.com/RCaAIPp5xU

— MetService (@MetService) February 16, 2018

WeatherWatch has advised people to postpone any non essential outdoors activities on Tuesday and Wednesday, especially hikers and trampers.

People are asked to check their emergency kits are up to date with enough food, water, batteries and cellphone chargers.

Gutters should be cleared in preparation and pets should be provided for too.

Cyclone Gita has been circling the Pacific Islands, where Tonga, Samoa and southern Fiji have been hit.

By the time the cyclone hit Tonga it was a category 4 and a state of emergency was declared.

Aid and supplies has since been sent to Tonga by the Defence Force.

Do I need to do anything before the storm hits?

A cyclone is a good reminder that in New Zealand we should all have emergency kits. Enough food and water for three days, per person. And don't forget your pets too.

Clear gutters (safely) on your house and road before heavy rain. Ensure gutters in your street are clear of leaves.

Have batteries for a radio. Have a charger for your cellphone that can be plugged into a car. Dust off the board games and get some junk food too maybe.

Hopefully it will pass your area without incident - but you need to be prepared for the worst in case the storm stalls or strengthens.

The projected path of the cyclone.

Will Gita be damaging?

It's always hard to answer this well in advance but the storm definitely has the potential to be damaging.

Two important factors remain: 1) The precise area of landfall and 2) the strength of the storm as it crosses New Zealand and moves away. We can't lock this in for another day or two so therefore it's hard to be more detailed on damage potential.

If Gita passes through New Zealand in less than 18 hours that will significantly reduce damage - if it lingers for over 24 hours, or 48 hours, then flooding and slips will become a bigger issue.

Keep in mind the mountains and ranges can make the weather more extreme for some, but soften conditions for others.

It's too early to know how this storm could behave here.

Generally speaking we expect power cuts, slips, trees down, some flooding and perhaps damage to some buildings (roofing iron, broken windows) but it is hard to be specific this far out.

Coastal flooding is also a possibility in western areas at high tides, including the upper North Island.

Many other areas may be entirely outside the risk of damage - keep an eye on the MetService warnings in the days before the storm hits and on our website too, which has daily news stories and maps.

Where will Gita make landfall?

Landfall is where the centre of the low crosses land. The worst of the winds, however, extend for 200 to 300 kms out from the centre. Landfall may occur anywhere from the upper West Coast of the South Island to the western side of the North Island south of Auckland.

Even if the centre doesn't make landfall near you it could still bring briefly destructive winds over a couple of hundred kilometers away from the centre.

Highest risks go from the West Coast, to central New Zealand right up to Auckland and Northland. That's quite a lot of space and a lot of towns, cities and farms.

We don't know yet how severe conditions might be in these areas - forecasts are still expected to change in the coming few days.

What sort of severe weather can we expect?

We can't lock this in yet - until we know the precise location of the centre of the low when it crosses New Zealand.

The mountains and ranges play a huge role in severe weather in New Zealand - making for stronger winds in some areas and heavier rain for others. So the tracking of the centre of the low along with the structure of the winds and rain are what we look for closer to the time and the day(s) itself.

How long will it last?

WIND: At this early stage the worst winds should last less than 24 hours and may affect regions across both islands. The very worst winds are likely to be within a 900km diameter. New Zealand is 1600kms long. This places a lot of people in the path of gale-force winds.

The storm may weaken more than is forecast - we'll keep you up to date. There's still a long way to go to lock in this info (at least another two or three days).

RAIN: At this stage the heaviest rain could last up to 48 hours for some areas in central New Zealand. There are two rain bands, one that will develop over New Zealand before the low and the other rain band attached to the centre of storm itself as it moves in.

Is this storm the same one that hit Samoa and Tonga?

Yes but it will be significantly weaker when it gets here. It will not be a Category 5 storm, latest models suggest it will have Cat 2 or 1 strength here.

Will it be a fizzer?

Sometimes tropical storms rush towards New Zealand then fade out just before they get here.

There hasn't been any model updates we trust that has suggested this although weakening is likely once it interacts with land. If it passes through faster than forecast - like Cyclone Cook did last year - then damage can be minimised greatly.

It's all about being prepared in case the worst happens. This storm has a huge amount of energy inside it and it will be spreading that energy further afield as it moves into New Zealand.

Is this just hype?

No. The potential for damage and risk to property and life is there with this storm if people aren't sensible (ie don't go tramping, sailing, crossing flooded rivers etc).

While the storm may weaken more than is currently forecast or hit parts of the country that can cope with severe weather there remains a significant chance that a few million people are in the path of severe weather - and these storms operate differently to most severe weather events New Zealand faces each month. It would be more dangerous to not talk about the risks.

Will this be like Bola or Giselle?

No two cyclones are the same. They are as individual and unique as human beings are. Every storm has a different history. In saying that, news reporters will always find someone who says "this was worse than Bola" - that can be locally true.

But each storm has a set of unique moving parts which means they all behave differently and often affect different places in different ways.

** Advice provided by WeatherWatch