Auckland tornado: Why it happened, and why we weren't warned

Monday, 21 June 2021

Residents in the south Auckland suburb of Papatoetoe are in shock after a tornado rolled through several blocks of houses, causing debris to go flying.

There wasn’t any way to predict the tornado that hit Auckland on Saturday morning, an expert says.

MetService meteorologist Lewis Ferris said while the conditions in which thunderstorms and tornadoes form can be forecast, “the ability to pinpoint when and where it will occur is not possible”.

Worker Janesh Prasad was killed, two people were injured, and 60 houses were left uninhabitable when the tornado ripped through the suburbs of Papatoetoe and Wiri in south Auckland.

The tornado left a trail of destruction in its wake.

Have you been affected by the tornado? Contact aucklandnewsroom@stuff.co.nz

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Aerial footage shows the extent of the damage in Papatoetoe.

The tornado was the product of an unstable atmosphere caused by warm air dragged down from the tropics, Ferris said.

An active rain band with embedded thunderstorm clouds resulted in the formation of the tornado, he said.

Because the tornado was so small and did not pass by any MetService weather stations, it wasn’t possible to estimate things such as wind speed, he said.

But while it was small, it was powerful.

While tornadoes in New Zealand tend to be little and very short-lived, “they can have disastrous impacts when they pass through a populated area”, Ferris said.

A major clean-up operation is underway in Papatoetoe, with many families unsure when they will be able to return home.

Auckland Emergency Management response teams have been out in the area, with waste collectors, street cleaners and building inspection teams deployed to the effort.

According to NIWA, Auckland is hit by a tornado on average less than once per year – but some years will see no tornadoes at all.

Across the country, MetService gets about 10 to 12 reported tornadoes a year.

Western areas tend to be impacted most and usually in the cooler months, Ferris said.

Tornadoes in New Zealand are usually between 20 and 100 metres wide and travel for two to five kilometres, lasting for a few minutes, according to NIWA.

While the main damage is confined to the path of the tornado, further damage can be caused when violent winds fling debris hundreds of metres away from the tornado.

The warning signs of a tornado include hail or heavy rain followed by dead calm or a fast, intense wind shift; a roar “like the sound of an approaching freight train”; a large, dark, low-lying cloud and a cloud of debris.