New weather warnings, watches issued with more tornadoes likely for large parts of New Zealand

The wild weather lashing New Zealand is expected to continue with new weather warnings and watches issued for large parts of the country and more tornadoes expected.

There have been four tornadoes over the last three days.

The first tornado hit east Auckland on Sunday evening leaving a trail of destruction. This was followed by another twister in the Tasman region on Monday, where around 12 roofs were lifted off homes.

On Tuesday morning, four homes were damaged and a teenager was injured after a tornado hit Paraparaumu. A smaller tornado also struck Waitara, Taranaki at about 1:15am, which saw a roof lifted off a house.

The wild weather comes as MetService issued new weather warnings and watches on Tuesday morning.

A severe thunderstorm watch has been issued for large parts of the North Island and parts of the West Coast of the South Island. 

The watch is issued for Buller, Westland, Northland, Auckland, Great Barrier Island, Coromandel Peninsula, Waikato, Waitomo, Taumarunui, Bay of Plenty, Rotorua, Taupo and Taranaki until Tuesday evening. 

"Rainfall of this intensity can cause surface and/or flash flooding, especially about low-lying areas such as streams, rivers or narrow valleys, and may also lead to slips," MetService said.

"Driving conditions will also be hazardous with surface flooding and poor visibility in heavy rain.

"Tornadic wind gusts can cause some structural damage, including trees and power lines, and may make driving hazardous. If any tornadoes occur, they will only affect very localised areas."

MetService urges Kiwis to take shelter immediately if severe weather approaches or "if you feel threatened".

A heavy rain warning is also in place for Westland about and north of Mount Cook, with residents warned to expect about 200mm of rain. 

The forecaster also said a heavy rain watch is in place for Tararua Range, Buller and the headwaters of the lakes and rivers of North Canterbury, while a strong wind watch is in place for Buller from around Seddonville southwards, and Westland from Harihari northwards.

MetService also warned Aucklanders to prepare for bad weather.

"AUCKLAND brace yourself for a wet, windy, and thundery spell later today. There's a risk of severe storms with downpours this afternoon and evening so take care and get prepared this morning, and keep an eye on the radar this afternoon," MetService said on Twitter. 

Three tornadoes in three days 'not unusual' - NIWA 

NIWA forecaster Chris Brandolino told AM on Tuesday three tornadoes in as many days is uncommon but "not unheard of". 

"It is unusual, it's not unheard of. We average about 7 to 10 moderate to strong tornadoes per year across New Zealand,"  Brandolino told AM co-host Melissa Chan-Green.

"There's a lot of variabilities. In some years it would be active e.g. now, in some years it will be inactive. So there's a lot of variability year to year and even decade to decade, but that's kind of the average over the long term."

NIWA forecaster Chris Brandolino.
NIWA forecaster Chris Brandolino. Photo credit: AM

Brandolino said the mix of warm, humid air and changing wind direction hitting New Zealand is creating perfect conditions for tornadoes.

"If you live in the upper North Island, it feels like summer so that's providing the fuel, the juice for thunderstorms. So you need warm, humid, moist air, that is a good start for a thunderstorm," he said.

"Then in order to get a tornado, you need air to basically what we describe as wind shear. So imagine you're in a hot air balloon. You are at the ground ready to take off and the wind is coming from the north, that's today. But as you ascend up and up and up, the wind actually changes direction… as you're going higher and higher, the wind goes from north to northwest and it also increases and that causes shear. 

"That causes the spin. So if you have this wind shear in an environment where there are thunderstorms that can often lead to these tornadic type situations."

Watch the full interview with Chris Brandolino in the video above.