The tornado that claimed the lives of three men in Hobsonville on Thursday could never have been predicted with current technology, experts say.
MetService meteorologist Daniel Corbett says the radar used by staff is unable to spot the smaller kind of twister likely to strike in New Zealand.
"Our tornadoes are only tens of metres wide," he says.
"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 tornadoes."
Mr Corbett says twisters in the US occur in the warm season but tornadoes here are largely a colder weather phenomenon.
"They're small, shortlived and dissipate within minutes."
Mr Corbett says the Hobsonville twister wasn't solely responsible for the destruction that caused around $11 million worth of damage - the straight line winds that went with it also played a part.
"At Whenuapai wind gusts of 110km were recorded and that alone can be very damaging."
He says the incident is a reminder to people to pay close attention to MetService warnings about strong winds and heavy rain.
The strip between Albany and Hobsonville has been hit by three deadly tornadoes in the past 20 years.
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