National Climate Summary – December 2006

WEDNESDAY 3 JANUARY 2007

National Climate Summary – December 2006: Rather cool

- Temperature: One of the coldest Decembers in the last sixty years
- Rainfall: Well below normal in the north of both islands; above normal in the east, especially Canterbury
- Sunshine: Sunnier than normal in the north of both islands
- Wind: More frequent cold southerlies

December was unusually cool for the time of year, due to more frequent southerly winds. Temperatures were 2 to 3 °C below normal (making it coldest start to December for many years) throughout New Zealand during the first half of the month, with little change during the last two weeks.

For the month, many locations experienced one of their coldest December’s on record. Wellington recorded its coldest December in more than 70 years, while New Plymouth, Wanganui, and Blenheim had their coldest December in at least 60 years. The national average temperature was 13.7 °C (1.9 °C below normal), the lowest for December since 13.4 °C in 2004 and equal with 1946. Rainfall was less than 50 percent (half) of normal in the north of both islands. However, it was quite wet, with at least 200 percent (twice) of normal rainfall, in some eastern parts of the country, especially in Canterbury. A sunny month occurred in parts of Northland, Auckland, Buller, Westland, and Nelson. More anticyclones (‘highs’) predominated in the Australian Bight, extending ridges of high pressure into the South Tasman Sea. Mean sea level pressures were below average northeast of the Chatham Islands. As a result, cold southerlies were more frequent than average over New Zealand.

Other Highlights:
 The highest temperature during December 2006 was 31.5 °C recorded at Blenheim Airport on the 12th.
 The lowest air temperature for the month was -2.5 °C recorded at Chateau Ruapehu on the10th.
 High rainfall occurred in Christchurch (74 mm) and over Banks Peninsula on the 20th, and in South Canterbury (with flooding in Ashburton) on the 29th.
 A hailstorm affected Riwaka on 1 December, with slight damage occurring to apples in some orchards.
 A wind gust of 148 km/h from the northwest was recorded at South West Cape on the 7th.
 Auckland was the warmest and driest, Christchurch the wettest, and Wellington the sunniest of the five main centres. Temperatures were well below normal in all five main centres. Rainfall was below normal in Auckland and Hamilton, above normal in Christchurch and Dunedin, and near normal in Wellington. Sunshine hours were above normal in Auckland, and near normal in the other centres.

Temperature: Mean temperatures were 2.0 to 2.4 °C below average in many regions, and more than 2.5 °C below average in Taupo and parts of Canterbury. Many locations experienced one of their coldest December’s on record.
Rainfall: December rainfall totals were less than 50 percent (half) of normal in parts of Northland, Waikato, Nelson, and central Marlborough. Rainfall was also below normal in much of Auckland, Waikato, Bay of Plenty, Westland, and Southern Lakes. In contrast, rainfall was about 200 percent (twice) of normal throughout much of Canterbury. Rainfall was also above normal in parts of Gisborne, Hawke’s Bay, and East Otago.
Sunshine: Sunshine hours and/or solar radiation were at least 110 percent of normal in parts of Northland, Auckland, Buller, Westland, and Nelson. Sunshine hours were below normal in Manawatu and on the Kaikoura coast.

For further information, please contact:
Dr Jim Salinger – Principal Scientist – Climate, NIWA National Climate Centre, Auckland,
Tel. (09) 375 2053 (work) or (027) 521 9468 (mobile) or (09) 576 9468 (Home)
Stuart Burgess – Climatologist – NIWA National Climate Centre, Wellington, Tel. (04) 386 0569

TEMPERATURES WELL BELOW AVERAGE THROUGHOUT NEW ZEALAND

The national average temperature was 13.7 °C (1.9°C below normal), the lowest for December since 13.3 °C in 2004 and equal with 1946. Mean temperatures were 2.0 to 2.4 °C below average in many regions, and more than 2.5 °C below average in Taupo and parts of Canterbury. Many locations experienced one of their coldest December’s on record.

Near or record low December mean air temperatures were recorded at:
Location Mean air
temperature
(ºC) Departure from
Normal Year
Records
began Comments
Kaitaia Airport 15.6 -2.5 1948 Lowest
Kaikohe EDR 15.1 -1.9 1973 Equal lowest
Whangarei Airport 16.6 -1.7 1967 Equal lowest
Warkworth 15.1 -1.9 1972 2nd lowest
Paeroa 15.4 -2.6 1947 2nd lowest
Auckland,Owairaka 15.4 -2.3 1949 Equal lowest
Whakatane Airport 15.4 -2.2 1974 2nd lowest
Rotorua Airport 13.8 -2.3 1964 2nd lowest
Taupo Airport 12.8 -2.9 1976 Lowest
Aukland, Mangere 16.0 -2.1 1950 2nd lowest
Auckland Airport 15.9 -2.2 1962 Lowest
Pukekohe 15.1 -1.9 1970 Lowest
Hamilton Airport 14.3 -2.3 1970 Lowest
Port Taharoa 15.4 -2.3 1982 2nd lowest
Te Kuiti 14.4 -2.4 1959 Lowest
Taumarunui 13.7 -3.0 1947 2nd lowest
New Plymouth Airport 13.7 -2.3 1944 Lowest since 1946
Lower Retaruke 13.7 -2.3 1966 2nd lowest
Castlepoint 13.7 -2.9 1972 Lowest
East Taratahi 13.9 -1.9 1972 2nd lowest
Napier Airport 15.4 -2.9 1973 2nd lowest
Whakatu 14.3 -2.9 1982 2nd lowest
Paraparaumu Airport 14.0 -1.9 1953 Equal lowest
Palmerston North Airport 13.8 -2.3 1962 Lowest
Palmerston North 13.5 -2.8 1928 2nd lowest
Wellington, Kelburn 12.9 -2.4 1928 Lowest
Wellington Airport 14.6 -1.8 1962 Lowest
Wallaceville 13.5 -2.0 1939 Equal 2nd lowest
Wanganui,Spriggens Park 14.1 -2.6 1937 Lowest
Hokitika Airport 12.6 -1.7 1963 3rd lowest
Reefton 13.4 -1.8 1960 Equal 3rd lowest
Nelson, Appleby 13.9 -2.2 1932 2nd lowest
Blenheim Airport 14.2 -2.1 1941 Lowest
Kaikoura 12.7 -2.6 1963 Lowest
Arthurs Pass 8.1 -3.1 1978 Lowest
Winchmore 12.3 -2.5 1949 2nd lowest
Christchurch Airport 13.3 -2.5 1953 2nd lowest
Timaru Airport 12.2 -2.1 1962 2nd lowest
Tara Hills 12.2 -2.2 1949 3rd lowest
Clyde 13.2 -2.4 1983 2nd lowest
Gore EDR 11.0 -2.2 1987 2nd lowest
Dunedin Airport 12.2 -1.6 1962 Equal 3rd lowest
Raoul Island 19.6 -1.3 1940 Equal 3rd lowest
RAINFALL WELL BELOW NORMAL RAINFALL IN THE NORTH OF THE NORTH ISLAND; WELL ABOVE NORMAL IN CANTERBURY

December rainfall totals were less than 50 percent (half) of normal in parts of Northland, Waikato, Nelson, and central Marlborough, and 75 percent (three quarters) or less of normal in much of AucklandBay of Plenty, Westland, and Southern Lakes. In contrast, rainfall was about 200 percent (twice) of normal throughout much of Canterbury. Rainfall was also above normal, with totals 125 percent (one and a quarter) or more of normal in parts of Gisborne, Hawke’s Bay, and East Otago. Rainfall was near normal elsewhere.

Near or record low December rainfall was recorded at:
Location December
Rainfall (mm) Percentage
Of normal Year
Records began Comments
Kerikeri EWS 22 21 1981 2nd lowest
Kerikeri Airport 34 28 1978 2nd lowest
Auckland, Henderson 41 45 1985 3rd lowest
Franz Josef 309 55 1982 3rd lowest

High December rainfall was recorded at:
Location December
Rainfall (mm) Percentage
Of normal Year
Records began Comments
Winchmore 147 244 1947 3rd highest
Middlemarch 128 187 2000 Highest

SUNNY IN THE NORTH OF BOTH ISLANDS

Sunshine hours and/or solar radiation were at least 110 percent of normal in parts of Northland, Auckland, Buller, Westland, and Nelson. Sunshine hours were less than 90 percent of normal in Manawatu, and on the Kaikoura coast, and near normal elsewhere.

DECEMBER’S CLIMATE IN THE FIVE MAIN CENTRES

Auckland was the warmest and driest, Christchurch the wettest, and Wellington the sunniest of the five main centres. Temperatures were well below normal in all five main centres. Rainfall was below normal in Auckland and Hamilton, above normal in Christchurch and Dunedin, and near normal in Wellington. Sunshine hours were above normal in Auckland, and near normal in the other centres.

Location Dec.
Mean
Temp.
(°C) Dep.
from normal
(°C) Dec.
rainfall
(mm) % of
Normal Dec.
Sunshine
(hours) % of
Normal
Auckland 16.0 -2.1 Well below normal 45a 49 Below normal 232 111 Above normal
Hamilton 14.4 -2.4 Well below normal 51 55 Below normal 218 98 Near normal
Wellington 12.7 -2.6 Well below normal 93 109 Near normal 241 106 Near normal
Christchurch 13.7 -2.3 Well below normal 123 249 Well above normal 208b 94 Near normal
Dunedin 12.2 c
-1.6 Well below normal 98 121 Above normal 167 99 Near normal
a Owairaka b Christchurch Airport c Dunedin Airport

HIGHLIGHTS AND EXTREME EVENTS

 Temperature
The highest temperature during December 2006 was 31.5 °C recorded at Blenheim Airport on the 12th, during hot dry northwesterly conditions, which also affected Canterbury. The lowest air temperature for the month was -2.5 °C recorded at Chateau Ruapehu on the10th.

Record low December minimum air temperatures were recorded at:
Location Minimum
air temperature
(ºC) Date of occurrence Year
Records
began
Pukekohe 4.4 10 Dec. 1970
Christchurch Airport 0.1 2 Dec. 1953
Manapouri, West Arm -0.6 1 Dec. 1996

 High rainfall
There were several high rainfall events, with at least 50 mm in 24 hours (the 29 December event produced flooding), during December. These were:

Date Region and location Rainfall
2 Dec. Fiordland Milford Sound (53 mm)
12 Dec. Fiordland Milford Sound (51 mm)
16 Dec. Southern Alps Mt Cook (56 mm)
19 Dec. Coromandel,
Southland Whitianga Airport (76 mm),
Secretary Island (85 mm)
20 Dec. Canterbury,
Banks Peninsula Christchurch, Kyle St. (74 mm),
Le Bons Bay (52 mm)
25-27 Dec. West Coast Milford Sound (232 mm over 2-days)
29 Dec. South Canterbury Ashburton (83 mm)

 Snowfall
Arthur’s Pass was closed due to snowfall over the night of 30 November/1 December. Sleet and snow were observed at Porters Pass on 30 December.

 Hailstorm
A hailstorm hit Riwaka at about 2pm on 1 December, with slight damage occurring to apples in some orchards.

 High winds
A wind gust of 148 km/h from the northwest was recorded at South West Cape on the 7th.

ENDS

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