Mini twisters drawn to Western Bay

The Western Bay may have escaped the destruction caused by this week's tornadoes but it remains a high risk area for such weather events.

WeatherWatch head analyst Philip Duncan said the geographical similarity of Auckland and Tauranga meant there was "quite a high risk" of mini tornadoes in the area.

He said the Auckland tornado was formed when a northwest front came over the Waitakere ranges and hit the sea.

The proximity of the Kaimai Range to the Papamoa and Mount Maunganui coasts meant there was potential for similar damaging weather events.

"Papamoa has a little bit of a history of having tornadoes and water spouts."

Mr Duncan said the twisters were caused by hot and cold air currents colliding and starting to mix and eventually swirl.

"The ingredients have to be pretty near perfect but once they get going they can be extremely destructive."

MetService forecaster Dan Corbett agreed mini tornadoes could not be ruled out for the Western Bay but were rare anywhere in New Zealand.

He said they were essentially thunderstorms that began to twist in the lower levels and sped up when they collided with a storm coming in from the sea.

Niwa records show nine instances of tornadoes or water spouts in the Western Bay between 1962 and 2009.

In May 2009 there were reports of up to four waterspouts off the Mount Maunganui coast near Mayor Island and five spotted off the coast of Town Point near Maketu, some estimated to be several hundred metres across.

A small twister hit Omanu beach and Arataki, ripping off roofing tiles and smashing windows a month after similar weather caused damage to homes in Papamoa in June 2008.

Tornadoes were also recorded in Tauranga in July 2007 and in Mount Maunganui in November 2006 and July 2004.

One of the most severe twisters flattened a cowshed, a car shed and the two cars in it and spread the wreckage across 20ha in Paengaroa in May 1968. The same storm flattened a fairly new two-storey house in Pukehina Beach.

Weather this weekend

• The week's gloomy weather should be a thing of the past by this afternoon. MetService forecaster Dan Corbett said it would be a day for outdoor activities. He said there may the odd shower which should clear throughout the afternoon. Sunday was also predicted to be fine. Mr Corbett said to expect a good start to next week as a nice high moves in across the country.