Experts agree event was a tornado

Weather experts have confirmed the damage inflicted across a swathe of the Karikari Peninsula on Sunday night ("There goes my retirement", August 14) was almost certainly from a tornado.

The twister is thought to have started about 9.30pm near the peninsula's western shore, crossing conservation land and Inland Road before ripping through at least two properties, wrecking a greenhouse and a chilli crop. A dinghy's flight was stopped only when its anchor became wrapped in a tree.

It then turned south and bowled about 500 exotic trees planted as a "retirement fund" by Andrew Potbury before continuing across farmland and dropping five pine trees on to State Highway 10 near the Inland Road intersection. Mangonui Fire Brigade spent three hours clearing the road.

Most of the trees on Mr Potbury's property had been planted in the mid-1990s, but a few were up to 50 years old and 20 metres high.

MetService meteorologist Daniel Corbett said Sunday night's conditions were just right for twisters, with very unstable air and "a lot of oomph" in the atmosphere. The forecast for the Far North had been for thunderstorms with a chance of tornadoes.

Karikari Peninsula was right on the edge of the MetService weather radar so it wasn't possible to confirm it was a tornado by its radar signature, but Metservice had received a number of reports of a twister east of Kaitaia on Sunday night.

New Zealand's tornadoes were small compared with those in North America but could still be nasty and inflict damage, Mr Corbett said.

Mr Potbury said he was fortunate because his home was undamaged and his family and animals unharmed. He was not sure if the same could be said for his neighbour's chickens - pieces of a brand-new chook house were scattered through what was left of his plantation - and his property was littered with dozens of dead birds, especially quail. He was hoping to catch and get help for a white-faced heron with a broken wing.

A fridge and barbecue had been blown off his verandah and an airborne trampoline had smashed the rear window of his four-wheel-drive.

The tornado brought down a power pole and lines near Lake Ohia, cutting off power to about 1200 Top Energy customers. Two more poles were pushed over where the tornado's path met power lines a second time. Ninety per cent of households had their power restored by 2am on Monday.

Other Northland tornadoes touched down in Kaitaia in July 2009 and in Waipu last July.

Meanwhile, the NZ Transport Agency has problems of its own in the form of a major subsidence on State Highway 10 just north of the Matauri Bay Road intersection, reducing the highway to one lane.

Bad weather earlier in the year had left that section of the highway unstable, NZTA spokesman Steve Mutton said, and repairs had been about to begin when the weekend storm struck.

Mr Mutton added that full repairs might now take several weeks given the extent of the subsidence.