December 2006

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

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.

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.

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.

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.

Full report

• Full details of the December 2006 Climate Summary

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.