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Today's tornado, which reportedly killed at least one person in the Auckland North Shore suburb of Albany, is the second fatal twister to hit the area in 20 years.
In May 1991, a tornado hit Albany, lifting roofing iron from homes and destroying a small church on the south-western side of the suburb. One man died when debris spread by the tornado hit him while he was driving a bulldozer.
Damaging tornadoes have a return period of about two or three years in Auckland and other previous incidents have included damage to buildings and power lines (August 1980; May 1982; September 1986; August 1992; March 1997), and up to 50 houses were damaged in August 1992. Tornados damaged fences and trees in August 1980; September 1986; and August 1992.
One of New Zealand's worst tornados was at Frankton, near Hamilton, in August 1948, when three people were killed.
Seven people were badly injured and damage to property was heavy.
Buildings were lifted from their piles, chimneys were snapped off, houses lost their roofs, trees uprooted and power and telephone lines were left hanging in the streets.
Reports at the time said the air was filled with flying corrugated iron, branches of trees, timber and other debris. Heavy rain accompanied the storm, with lightning and thunder.
Another three people died in a tornado near Waitara, Taranaki in 2004.
Tornados are a mass of unstable air rotating at up to 244kmh which rises rapidly around a centre of unstable air.
WeatherWatch website analyst Philip Duncan said today's Albany tornado probably had windspeeds of around 200kmh.
"We've had reports of cars lifted and thrown, roofs taken off and trees uprooted, which is consistent with... winds averaging somewhere between 180kmh and 220kmh."
Mr Duncan said the threat of further tornados in Auckland late today had eased but the risk had shifted south into Waikato, Coromandel Peninsula, Great Barrier Island and Bay of Plenty.
Waterspouts were also possible around Great Barrier Island, Coromandel Peninsula and Bay of Plenty, he said.
Tornados occur frequently in Auckland but are usually much smaller than the large devastating ones that roar across in the midwest of the United States, civil defence officials say.