2005

Tuesday, 10 January 2006

Summary

Much warmer, with more anticyclones and less wind than normal
Very low rainfall in the South Island
Catastrophic floods and extremely high rainfall in Bay of Plenty; destructive tornadoes; an unseasonable late snowstorm

New Zealand’s climate for 2005 was marked by too little rain in some places, and too much in others. Principal scientist Dr Jim Salinger of the NIWA National Climate Centre, says "Rainfall during the year was less than 75 percent of normal over much of the South Island whereas severe flooding in the Bay of Plenty in May caused widespread damage. "The national average temperature of 13.1°C made 2005 the fourth warmest year nationally since reliable records commenced in the 1860s. Only 1971, 1998 and 1999 have been warmer with temperatures of 13.2, 13.3 and 13.3 °C respectively. Notable climate features in various parts of the country included heat-waves, low soil moisture, the Greymouth tornado, an unseasonable snowstorm, and damaging hailstorms. The year was dominated by more anticyclones with less wind than average, although more easterlies at times occurred on to the north east of the North Island."

"A weak El Niño prevailed in the equatorial Pacific during the first part of the year. More anticyclones in January commenced the trend of low rainfall and severe or significant soil moisture deficits in the northern half of the North Island and Canterbury; these conditions persisting into April. Anticyclones and northeasterlies brought one of the warmest Februaries on record, with maximum temperatures of 30°C or more in many locations throughout New Zealand, and temperatures of 35°C or more in sheltered inland areas of the South Island during the first 10 days. March was wetter in the North Island, but more anticyclones in April kept conditions dry. However, weather patterns changed abruptly in May. The Bay of Plenty floods of 3-4 May and 17-18 May were most disastrous, the earlier of the two causing widespread damage in parts of Tauranga, and the later being phenomenal, with unprecedented high-rainfall for the district and a state of emergency declared from Tauranga to Matata. Hundreds of people were evacuated. Homes were destroyed by mudslides and floodwaters and rising waters threatened hundreds of others. Flooding was extreme in Matata, where a stream became a torrent of water, mud, huge boulders, and debris", says Dr Salinger.

Halfway through the year, more frequent anticyclones over the North Island and north westerlies over the South Island produced the sixth warmest winter on record, with extremely dry conditions in the east of the South Island. "Winter snowfall was much less frequent than normal. However, an early spring occurrence (on 19 September) to sea level in Canterbury was unusual for the month", says Dr Salinger. This resulted in the closure of Christchurch Airport, along with schools and universities, with snow depths of 5-10 cm in the region. Power cuts also occurred. Hundreds of newborn lambs died in the cold.

More anticyclones over New Zealand continued into early spring, with milder conditions and below average spring rainfall, which resulted in significant soil moisture deficits developing much earlier than usual from Southland to Marlborough, and spreading to Nelson and the southwest of the North Island in November, and developing in Hawke’s Bay, Auckland, and parts of Northland in December. However southeasterlies in both October and November produced significant flooding in Gisborne. Patterns changed with warm northerlies producing the 3rd warmest December month.

"For the year there were at least 26 heavy rainfall events, half of which produced floods," said Dr Salinger. There were also seven damaging hailstorms, and twelve damaging tornadoes (or events attributed to tornadoes) in 2005," said Dr Salinger. The Greymouth tornado of 10 March was particularly destructive for a New Zealand occurrence, leaving 30 people homeless, and resulting in damage worth at least $10 million. Wellington Airport was closed for many more hours than usual in 2005. There were 52 hours with fog there, the highest for any year in 45-years of measurement.

NIWA analyses of month-by-month records and preliminary end of year data show:

  • The year’s national average temperature of 13.1 °C (0.5 °C above the 1971-2000 normal), was the fourth warmest nationally since reliable records commenced in the 1860s.
  • The highest annual mean temperature recorded for the year was 16.1 °C recorded at both Cape Reinga and Whangarei Airport.
  • The highest recorded extreme air temperature for the year was 38.7 °C recorded at Alexandra on 5 February (the highest temperature there for any month, in records back to 1929). This is only one a few occasions when temperatures in New Zealand have exceeded 100 °F (37.8 °C).
  • The highest temperatures during August 2005 were 25.1 °C recorded at Hanmer Forest on the 30th, and 25.4 °C recorded in Amberley on the 31st. These both exceeded the previous all-time New Zealand maximum temperature record for August.
  • The lowest temperature for the year was -9.5 °C, recorded at Ophir (Central Otago) on 17 July.
  • February was the 8th warmest on record.
  • June was the coldest in a decade.
  • July was the 3rd warmest on record.
  • August was the 4th warmest on record.
  • December was the 3rd warmest on record.
  • The driest rainfall recording locations were Clyde in central Otago with 348 mm of rain for the year, followed by Lake Tekapo with 352 mm.
  • Christchurch was easily the driest of the four main centres with 450 mm and Auckland the wettest with 1112 mm. Wellington received 975 mm and Dunedin 647 mm.
  • Of the regularly reporting gauges, the Cropp River gauge in Westland, inland in the headwaters of the Hokitika River, recorded the highest rainfall with a 2005 annual total of 9290 mm.
  • Nelson was the sunniest centre in 2005, recording 2571 hours, followed by Tauranga with 2495 hours, then Blenheim with 2466 hours. Auckland was easily the sunniest of the four main centres with 2254 sunshine hours, followed by Wellington (2211 hours) and Christchurch (2055 hours). Dunedin recorded 1807 hours.
  • The highest recorded wind gust for the year was 174 km/h from the northwest, recorded at Southwest Cape (Stewart Island) on 3 April.

Prevailing climate patterns – a weak El Niño early in the year

Overall, mean sea level pressures were above average over much of New Zealand, with more anticyclones ('highs') than average in the Tasman Sea and to the east of the South Island. This pattern resulted in less wind than is normal over much of New Zealand. February, March, May, and December were the only months when more lows (cyclonic anomalies) occurred over New Zealand. Low pressure systems prevailed in the Tasman Sea and over central New Zealand during those months.

A weak El Niño prevailed in the equatorial Pacific during the first half of the year. Sea temperatures around New Zealand were 0.5°C above average, being warmer than normal in all months except January.

Extremely low rainfall over much of the South Island; High rainfall in Bay of Plenty and Hawke's Bay

2005 was one of the driest on record in parts of Marlborough and Canterbury, as well as in eastern Northland, Nelson, and parts of the West Coast. In contrast, it was one of the wetter years on record in parts of Bay of Plenty, and Hawke’s Bay. The year was much drier than average (with totals less than 75 percent of normal) throughout much of the South Island. Totals were also below average (75 to 90 percent of normal) in the north and west of the North Island from Northland to Wellington (excluding Wanganui), as well as southern Wairarapa. However, rainfall was well above average (more than 125 percent of normal) in western Bay of Plenty, Hawke’s Bay, and the far southwest of the South Island. Rainfall was near normal elsewhere.

Extremely low annual rainfall, for the year 2005, was measured at:

Location 2005 rainfall (mm) Percentage Of normal Year Records began Comments
Whangarei Airport 984 66 1937 2rd lowest
Takaka 1315 59 1986 Lowest
Reefton 1298 65 1961 Lowest
Franz Josef 3757 64 1983 Lowest
Motueka 895 64 1943 2nd lowest
Nelson Airport 644 68 1941 Lowest
Appleby 646 65 1932 2nd lowest
Blenheim Airport 506 70 1941 2nd lowest
Hanmer Forest 698 59 1905 3rd lowest
Mt Cook Village 2701 63 1930 3rd lowest
Darfield 484 61 1920 Lowest
Lake Tekapo 352 59 1927 2nd lowest
Tara Hills 366a 69 1950 Lowest
Wanaka Airport 444 63 1993 Lowest

a 4-days missing

High annual rainfall, for the year 2005, was measured at:

Location 2005 rainfall (mm) Percentage of normal Year Records began Comments
Tauranga Airport 1681 139 1898 Well above average
Napier Airport 1055 127 1951 3rd highest
Puysegur Point 2659 130 1994 Well above average

Of the four main centres, Christchurch (Airport) was the driest with 450 mm (69% of average) and Auckland the wettest with 1112 mm (90% of average). Wellington received 975 mm (78%) and Dunedin 647 mm (80%).

Clyde, in Central Otago, was the driest of the sites where NIWA records rainfall, with only 348 mm (76% of average), followed by Lake Tekapo with 352 mm (59% of average). Of the regularly reporting rainfall stations, the wettest location in 2005, for which rainfall data are presently available was the Cropp River gauge in Westland, inland in the headwaters of the Hokitika River, with an annual total of 9290 mm.

2005 much warmer than normal

The national average temperature in 2005 was 13.1 °C, 0.5 °C above the 1971 – 2000 normal. It was the fourth warmest year nationally since reliable records commenced in the 1860s. Only 1971, 1998 and 1999 have been warmer with temperatures of 13.2, 13.3 and 13.3 °C respectively. For New Zealand as a whole, there were seven warmer than normal months (February, March , May, July through September, and December), two cooler (January and April) and three months with mean temperatures close to the climatological average (June, October and November). February with a mean temperature of 18.6 °C (1.3 °C above normal) was the 8th warmest on record, July with 9.1 °C (1.2 °C above normal) was the 3rd warmest on record, August with 9.8 °C (1.1 °C above normal) was the 4th warmest on record, and December with 17.5 °C (1.9 °C above normal) was the 3rd warmest on record. 2005 mean temperatures were at least 0.3 °C above average in most regions, and 0.5 to 0.9 °C above average in parts of Auckland, Coromandel, western Bay of Plenty, the west of the North Island from Wanganui to Wellington, as well as Wairarapa, and much of the South Island. Temperatures were near average in coastal Wairarapa, along the Kaikoura Coast, and in coastal areas of south Canterbury. The warmest locales were Cape Reinga and Whangarei Airport, both with a mean temperature for the year of 16.1 °C (0.2 and 0.5 °C above normal respectively).

Well above normal mean temperatures for the year 2005 were measured at:

Location Mean temperature (°C) Departure from normal Year Records began Comments
Dargaville 15.6 +0.6 1944 3rd highest
Auckland, Henderson 15.7 +0.6 1986 3rd highest
Pukekohe 15.3 +0.8 1971 2nd highest
Motu 11.7 +1.1 1995 Highest
Chateau Ruapehu 8.2 +0.8 1933 Equal 2nd highest
East Taratahi 13.0 +0.9 1973 Well above normal
Wanganui 14.7 +0.8 1938 Highest
Palmerston North 13.9 +0.6 1928 Equal 2nd highest
Wallaceville 13.1 +0.7 1940 Equal 3rd highest
Kelburn, Wellington 13.5 +0.6 1928 Equal 3rd highest
Farewell Spit 14.5 +1.1 1972 Highest
Nelson Airport 13.4 +0.9 1944 3rd highest
Blenheim Research 13.6 +0.6 1987 Equal 2nd highest
Tara Hills, Omarama 10.2 +0.8 1950 2nd highest
Wanaka Airport 11.4 +0.7 1993 Highest
Queenstown 11.6 +0.9 1872 2nd highest
Lauder 10.5 +0.9 1982 Highest
Clyde 11.2 +0.7 1984 Equal highest
Invercargill Airport 10.7 +0.8 1949 Equal highest
Campbell Island 7.5 +0.4 1944 3rd highest

Sunny in many western regions, as well as southern regions of the South Island, near normal elsewhere

Sunshine hours were more than 110 percent of normal in Northland, Auckland, Buller, Westland, Southland, and coastal Otago, and at least 105 percent of normal in Taranaki, Gisborne, Hawke’s Bay,Wairarapa, Manawatu, Kapiti, Wellington, Nelson, and inland areas of south Canterbury. They were near normal in all other regions.

Nelson was the sunniest centre in 2005, recording 2571 hours, followed by Tauranga with 2495 hours, and then Blenheim with 2466 hours.

Total sunshine hours for the year 2005 in selected main centres were:

Location 2005 Sunshine (hours) Normal (hours) Departure from normal Comments
Auckland 2254 2019 +12% Highest for Mangere, records began in 1963
Wellington 2211 2064 +7% Above normal
Christchurch 2055 2100 -2% Near normal
Dunedin 1807 1597 +13% Above normal
Invercargill 1785 1609 +11% Above normal
Tauranga Airport 2495 2250 +11% 3rd highest, records began in 1933
New Plymouth 2377 2171 +9% Highest since 1943, records began in 1916

Full report

Climate Summary for 2005 (PDF 118 KB)

For further information, please contact:

Dr Jim Salinger – Principal Scientist, Climate
NIWA National Climate Centre – Auckland
Phone +64 9 375 2053
j.salinger@niwa.co.nz

Stuart Burgess – Climatologist
NIWA National Climate Centre – Wellington
Phone +64 4 386 0569
s.burgess@niwa.co.nz

Geoff Baird – Communications Manager
Phone +64 4 386 0543
g.baird@niwa.co.nz

Acknowledgement of NIWA as the source is required.