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Last year's topsy-turvy mix of droughts, floods and tornadoes proved costly for New Zealand.
The National Institute of Water and Atmospheric Research yesterday released its 2007 national climate summary, which highlighted the disastrous floods in Northland, droughts in the eastern North Island and destructive tornadoes and windstorms.
Auckland
was the wettest of the five main centres and Wellington the sunniest - 2007 was the capital's third sunniest year since 1928.
Principal climate scientist Jim Salinger said the severe weather proved expensive for the country.
The North Island drought was thought to have sucked about $700 million out of the economy and insured losses from floods, frosts and wind damage were estimated at about $100 million.
Dr Salinger said 2007 provided too little rain in many places, with record low rainfalls in places such as New Plymouth and Palmerston North.
Rainfall was less than 60 per cent of normal in parts of Marlborough, Canterbury and Central Otago.
Dr Salinger said the national average temperature was 12.7C, just 0.1C above normal.
May was the warmest on record but had been offset by some cooler months.
Dr Salinger said warmer than normal seas to the west, anticyclones to the east and frequent warm northwesterlies had produced the record high mean May temperatures.
The national average temperature in May was 12.4C (1.7C above normal), the highest for New Zealand in reliable records dating back to the 1860s.
It was also the driest May on record in the north of the North Island and the east of the country.
Dr Salinger said although New Zealand had a relatively warm winter, he felt there was nothing in the data that could be attributed specifically to global warming, and global weather figures showed 2007 was the seventh warmest year on record for the world.
However, the floods in Northland, which were one-in-150-year events, were an example of the type of heavy rainfall episodes that would become more frequent this century, he said.
The most disastrous floods for many decades had occurred in the Far North and Whangarei districts, especially in the Bay of Islands at the end of March, due to exceptionally high rainfall, from 250mm to more than 400mm.
More Northland floods followed in July, with windstorms that also hit Auckland and the Coromandel.
Dr Salinger said there were numerous heavy rainfall events during 2007, of which about nine produced floods.
There were 14 damaging tornadoes, an early autumn and late-spring hot spell, two severe hailstorms and seven damaging electrical storms.
The most significant extreme event of the year was the extraordinary swarm of tornadoes that wreaked havoc throughout Taranaki over July 4-5 as active frontal bands crossed the country from the Tasman Sea.
Dr Salinger said 2007 had begun with low rainfall and significant soil moisture deficits, especially in the east, which persisted in the east of the North Island until May. July was a month of extremes and contrasts with floods, windstorms and tornadoes.
Dr Salinger said 2007 had seen a swing from an El Nino to a La Nina climate pattern.
From September, La Nina conditions had developed in the tropical Pacific, with a noticeable increase in the frequency and strength of the westerlies over New Zealand in October and then a significant drop in windiness from November.
There were more anticyclones, or highs, over New Zealand than usual.
October was rather stormy and generally cold with deep depressions tracking south of New Zealand and frequent westerly gales, making it the fourth windiest October overall.
The highest annual mean temperature recorded for the year was 16C, at Whangarei Airport.
The highest recorded extreme temperature of the year occurred in Hawkes Bay - 33.5C at Napier Airport on January 22 during hot dry northwesterly conditions.
The lowest air temperature was minus 15.4C recorded at Lauder in Central Otago on July 18, the lowest there since July 1995.
Blenheim was the sunniest centre in 2007, recording 2567 hours, followed by Lake Tekapo with 2554 hours and Whakatane with 2551 hours.
Northland was the only region where rainfall was above average.
For New Zealand as a whole, there were five warmer-than-normal months (March, May, July, August and December) and five-cooler-than normal months (January, April, June, October and November).
