A major change in our weather pattern arrives this afternoon in the South Island and tomorrow in the North Island as the roaring 40s surge up over New Zealand says WeatherWatch.co.nz.

Strong winds are building over the nation today ahead of what will be a rough few days ahead with severe gales, turbulent flights, thunderstorms, squalls and even tornados.

The onslaught will be mainly in the west with strong winds roaring around a large high over southern Australia and deep lows in the South Ocean.  “New Zealand is smack bang in the middle of this squash zone” says head weather analyst Philip Duncan.

“We are in for several very windy days with west to south west winds, a drop in temperatures and the chance of thunderstorms, squalls and even a few tornados”.

The tornado risk, issued by WeatherWatch.co.nz yesterday, mostly covers the West Coast but is likely to extend into Taranaki, then on Sunday right up the west coast to cover Waitomo, Waikato, Auckland, Northland and then later into Coromandel and Bay of Plenty.

Tornados aside, localised bursts of wind within squalls could cause damage to trees, powerlines and even lift roofs.

“This is not the same weather set up as the Albany tornado two weeks ago.  This is a far more wild and Autumn-like set up” says Mr Duncan “and the risk area is much greater, covering northern and western parts of both islands”.

He stresses that while conditions are very good for producing small scale tornados (EF0 or EF1 rated) over the coming 48 hours the odds are usually stacked against one hitting people and property.  “We you look at New Zealand via Google Earth you can really see that much of our country is forestry or farmland.  Every year New Zealand is hit by tornados but most of them we don’t even know about or see damage from”.

And it’s not just WeatherWatch.co.nz warning of potential severe weather.  Metservice has gone all out identifying numerous regions which may face damaging winds, rain warnings and tornados (see maps below).

These are the Metservice thunderstorm outlooks as of 11:15am on Saturday May 14th.

Map 1 – Valid to Midnight tonight

Map 2 – Valid from midnight tonight to noon Sunday

Map 3 – Valid noon Sunday to Midnight Sunday

From Metserice – regarding Map 3 – The front is expected to move over the North Island during the afternoon and evening and there is a high risk of thunderstorms developing from Northland down to Taranaki and the Bay of Plenty, and there is a low risk that some of these thunderstorms will be severe, with damaging wind gusts above 110 km/h.

Otherwise, these thunderstorms could be accompanied by localised heavy rain and possible tornadoes. The thunderstorms are expected to clear west of Tauranga late afternoon and elsewhere late evening.

Another front should move onto the South Island during the afternoon and evening.

There is a moderate risk of thunderstorms for Fiordland and coastal Southland during the afternoon. Initially these thunderstorms are likely to be accompanied by localised heavy rain, strong wind gusts and possibly tornadoes,but in the evening, the risk of tornadoes and heavy rain reduces but there is possibility of some hail.

The moderate risk of thunderstorms spreads into Westland and Buller during the evening, bringing the possibility of localised heavy rainfall, strong wind gusts and possibly tornadoes.

There is a low risk of thunderstorms also developing in Clutha, inland Southland and northwest Nelson.

-WeatherWatch.co.nz with MetService