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
[email protected]

Stuart Burgess – Climatologist
NIWA National Climate Centre – Wellington
Phone +64 4 386 0569
[email protected]

Geoff Baird – Communications Manager
Phone +64 4 386 0543
[email protected]

Acknowledgement of NIWA as the source is required.