Tornado risk for NZ as storm approaches

Forecasters are predicting heavy rain, gales, thunder and possible tornados over the next three days. Photo / Supplied

New Zealand is in for stormy weather over the next three days, with weather forecasters predicting possible small tornadoes.

A storm in the Southern Ocean is moving into the Tasman Sea and will cross new Zealand bringing the risk of thunder, gales and heavy rain.

Snow, hail and sunshine are also in the mixed-up forecast, according to WeatherWatch.co.nz.

Head weather analyst Philip Duncan says the chance of this system producing a tornado is fairly high but stresses it may create only one or two across the entire country.

"We have all the right ingredients for nasty squalls and heavy showers and with so much activity a couple of small tornados are likely around our more coastal regions in the west and north".

Mr Duncan says the system rolling in is very similar to one that affected New Zealand in early July last year and produced a damaging tornado in Kapiti, along with numerous other thunderstorms and strong winds across the country.

"While we feel quite confident this system has the potential to create a tornado it's very important to focus on the fact that much of the west coast of both main islands is rural farmland, national parks and bush. We may have one [tornado] and never know about it".

Mr Duncan says if people see a tornado the safest place is indoors in a small room.

He said: "Stay away from windows and don't listen to the myth of opening windows on the sheltered side of the house. Just get into a small room or closet until it passes".

WeatherWatch.co.nz says it's rare for a tornado to hit a home but in the past two years numerous properties around the country have been damaged by them and one person was killed in Albany last May after a tornado ripped through a shopping centre.

Tomorrow is due to be mostly warm, with strong winds from the west to north west to continue to affect parts of the country, especially central New Zealand and the North Island.

During Tuesday and Wednesday the wind flow will shift more southerly and then very cold air will move in.

Snow is expected to settle to about 300 metres in the South Island on Tuesday night and into Wednesday.

While snow currently isn't predicted for any of the main centres, WeatherWatch.co.nz says Dunedin's hill suburbs may get sleet overnight Tuesday and Queenstown will be borderline for snow.

Hail and very cold south to south west winds will mostly affect the southern and western coastlines of New Zealand on Tuesday and Wednesday, easing Thursday.

For Canterbury the wind may be too westerly to see much precipitation from this system. While highs on Tuesday will likely be under 12 degrees for the region the chance for rain is currently only 40 per cent.

In a similar storm in July last year, Canterbury enjoyed mostly sunny weather while lightning from the West Coast could be seen at night lighting up clouds on the Southern Alps.

The overall system is so large it is predicted to continue to affect New Zealand until Thursday, with a large high expected to push in from the Tasman Sea this Friday and into next weekend.