Was it a tornado that caused destruction in Northland?

The AM Show 06/06/2019

The severe weather event that ripped through the Far North on Wednesday and damaged more than 20 houses was likely not a tornado, according to a weather forecaster.

On Wednesday, more than 20 houses were damaged by a devastating weather system that ripped through parts of the Far North, including Coopers Beach.

Social media was inundated with pictures of the destruction with residents saying it had been caused by a tornado.

But one weather forecaster says it may not have been a tornado, but simply strong gusts of "unidirectional" wind that rattled the community.

The National Institute of Water and Atmospheric Research (NIWA) forecaster Chris Brandolino told The AM Show there are several "special ingredients" that made a tornado, and from what he had seen of Wednesday's event, they weren't all in the mix.

"Looking at the way the atmosphere was structured, it's unlikely it was [a tornado]. It was likely a microburst, straight-line winds," he said.

"The winds were pretty unidirectional, they came from the same direction, the route, the vertical - it means basically the wind didn't change direction with height, which means there probably wasn't any spin."

According to AccuWeather, a microburst is a "weather phenomenon" which can cause destruction that is "just as devastating as a tornado".

A microburst is a small column of exceptionally intense and localised sinking air that results in a violent outrush of air at the ground.

"It is capable of producing damaging straight-line winds of more than 100 mph (160km/h) that are similar to that in some tornadoes, but without the tornado's rotation."

Brandolino says, for a tornado to occur, there needs to be a thunderstorm and the air needs to spin and change direction with height.

"At the surface, let's say it is northerly, and as you go up, the wind changes anti-clockwise as you go up in elevation, that creates spin, we call that shear.

"That shear creates the spin necessary for the air to rotate in a tornado."

He said New Zealand rarely sees the destructive tornadoes that are regular in parts of the United States as we don't have the right sort of climate.

"The reason we won't get those is because we are a marine climate - we need those big temperature differences, like a continent, to really fuel temperature difference, energy, thunderstorms.

Without that huge thunderstorm presence, a lot of energy, you are not going to get those big tornadoes.

But while the weather event may not technically be a tornado, Newshub's reporter on the ground, Alice Wilkins, told The AM Show that residents certainly thought a tornado had come their way on Wednesday.

"The residents here have described it as a tornado.

"Metservice had issued a severe thunderstorm warning the night before, and that had the potential for tornadoes to hit within it, and the residents here say that is what they saw."

Wilkins described hearing of roofs being lifted from homes, trampolines flying through the air, fences being flattened, and of one home which had a piece of plywood lodged into it like an arrow.

One resident hid in a cupboard after seeing "bits of iron and debris that had been picked up flying through the air", while a man compared the sound of the event as similar to a "freight train".

Residents described the system as moving through the region very quickly and sporadically.

Suspected tornado in the Far North. Photo credit: Supplied.
Destruction from the weather event. Photo credit: Supplied.
Destruction from the weather event. Photo credit: Supplied.

Wilkins said most of the area had already been cleaned up, but Far North Mayor John Carter said people would be checking over houses in Coopers Beach to make sure they had an accurate idea of how many had been damaged.

"At the moment, we are talking about 20 homes, but we are not sure if there may be more damage than that, and it could be as many as 30 or 40 because it is scattered," he told The AM Show.

"If people have homes up here at Coopers Beach and they are not occupied, can they get their agents to come and have a look, and let us know if there is any damage."

He thanked those who had "stood up" and helped affected residents.

"I have got to recognise the resilience of the people, the Civil Defence, the fire brigade, the police, and most importantly, the neighbors who helped others out, who have been challenged."

Auckland was also impacted by the wet weather on Wednesday, with a large number of lightning strikes and flooding in some areas.

Thursday isn't expected to have such severe weather, but it could still be wet and chilly in some western regions.

The AM Show / Newshub reporter Jamie Ensor