'Tornado alley' terror

20:20, Dec 10 2012
Auckland thunderstorm
A motorist captured this picture on Auckland's North Shore as grey clouds hit the city.
Auckland thunderstorm
Heavy rain causes flash flooding just after midday in Auckland.
Auckland thunderstorm
Guttering fails to cope with the heavy rain in Auckland.
Auckland thunderstorm December 5
The view from a city centre office, taken by a Twitter user.
Auckland thunderstorm December 5
Flooding begins in Glen Eden.
Auckland thunderstorm December 5
Dark clouds gather over Takapuna.
Auckland thunderstorm December 5
The storm rages in Hobsonville.
Auckland thunderstorm December 5
The aftermath of the tornado in Hobsonville.
Auckland thunderstorm December 5
Sharon White with her three year old son, and their overturned trampoline.
Auckland thunderstorm December 5
Emergency services arrive in Hobsonville.
Auckland thunderstorm December 5
Heavy rain at the Dotcom mansion.
Auckland thunderstorm December 5
Storm damage in Hobsonville.
Auckland thunderstorm December 5
Storm damage in Hobsonville.
Auckland thunderstorm December 5
Storm damage obstructs a road.
Auckland thunderstorm December 5
Storm damage in Hobsonville.
Auckland thunderstorm December 5
Storm damage in Hobsonville.
Auckland thunderstorm
Damage to housing in Hobsonville.
Auckland thunderstorm December 5
Inner Auckland is hit with rain.
Auckland thunderstorm December 5
Auckland city around noon today, from www.sitecam.co.nz/auckland_webcam/.
Auckland thunderstorm December 5
Emergency services work to free people trapped by a concrete slab on a building site in Hobsonville.
Auckland thunderstorm December 5
Destruction on Wallingford Way in Hobsonville.
Auckland thunderstorm December 5
Emergency services work amongst destruction on Wallingford Way in Hobsonville.
Auckland thunderstorm December 5
Emergency services work amongst destruction on Wallingford Way in Hobsonville.
Auckland thunderstorm December 5
Destruction on Wallingford Way in Hobsonville.
Auckland thunderstorm December 5
Destruction in Hobsonville.
Auckland thunderstorm December 5
A trampoline flung into a house in Hobsonville.
Auckland thunderstorm December 5
An emergency worker in Hobsonville.
Auckland thunderstorm December 5
The remains of a double car garage in Whenuapai.
Auckland thunderstorm December 5
Damage in Hobsonville.
Auckland thunderstorm December 5
Road flooding in Auckland.
Auckland tornado
Fire rescue crew work to free people trapped by a concrete slab on a building site near Walingford Way in Hobsonville.
Auckland tornado
A fire rescue crew at a building site near Walingford Way in Hobsonville.

Northwest Auckland has been hit by three deadly tornados in 20 years but it would have been impossible to predict the tornado that claimed the lives of three men on Thursday, an expert says.

MetService meteorologist Daniel Corbett said the mixture of temperatures coming from the land and the sea, combined with wind speed, made it an ideal area for tornados to form.

Corbett said meteorologists could not predict tornados in the area. A radar used by staff was unable to spot the smaller kind of twister likely to strike in New Zealand.

"Our tornados are only tens of metres wide," he said.

"In the United States they are half-a-mile wide and the radar can pick up the whole thunderstorm turning.

"Because of the localised nature of these events they are undetectable and we have to forecast the conditions that would be favourable for tornados."

Twisters in the US occur in the warm season but tornados here were largely a colder weather phenomenon, he said.

"They're small, short-lived and dissipate within minutes."

Corbett said the Hobsonville tornado wasn't solely responsible for the destruction that caused about $13 million worth of damage - the straight line winds that went with it also played a part.

"At Whenuapai wind gusts of 110kmh were recorded and that alone can be very damaging."
 
He said the incident was a reminder to people to pay close attention to weather warnings about strong winds and heavy rain.

"Those are the days you want to plan to be at home or work and not be going out to the park.

"If you're in a tornado at home get into a closet or cupboard or go to the middle of your house keeping well away from glass. Otherwise get into your car if you've got nothing else."

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Auckland Tornado graphic
DEADLY TORNADOS: Lives lost and damaged done by tornadoes in northwest Auckland.

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