December 2007

Warm in many regions; severe soil moisture deficits persist in the east and inland areas of the South Island

• Rainfall: Below normal rainfall in Bay of Plenty, south west of North Island and inland areas of the South Island, very wet start to December in Northland
• Temperature: Above average in the north and west
• Sunshine: Well above average in the south, well below average in the north

December 2007 was characterised by near or below normal rainfall in many regions of New Zealand. Severe soil moisture deficits (more than 130 mm) persisted from November in Marlborough, Canterbury, North and Central Otago, with significant soil moisture deficits (more than 110 mm) occurring in Auckland, Bay of Plenty, Taranaki, Wairarapa, Manawatu, and Nelson. The month had a wet start in Northland (with rainfall to the 10^th totalling almost 200 mm in the Bay of Islands), followed by more settled conditions. December 2007 temperatures were above average in most northern and western regions, as well as Southland and much of Otago, but near average in the east. The national average temperature of 16.1 ºC was 0.5 °C above average. Southland and Otago basked in well above average December sunshine. However, cloudy skies prevailed with near or record low December sunshine hours in parts of Northland, Waikato, and Taranaki. The month’s overall climate pattern was produced by more frequent anticyclones east of the South Island with troughs of low pressure over north Tasman Sea, typical of La Niña conditions. This resulted in more frequent dry northeasterlies than usual over New Zealand.

Further Highlights

• The lowest air temperature during the month was -1.7 ºC recorded at Hanmer Forest on the 8^th. The highest temperature during December 2007 was 32.8 ºC recorded at Christchurch Airport on the 11^th.
• Persistent rainfall occurred in Northland, with almost 200 mm in the Bay of Islands between 1-10 December. Periods of persistent heavy rainfall occurred on the West Coast of the South Island, with as much as 560 mm at Franz Josef between 9-17 December and 258 mm at Milford Sound between 23-30 December.
• The highest wind gust of the month was 132 km/h from the northwest, recorded at South West Cape on the 30^th.
• Of the five main centres, Auckland was the warmest, Wellington the wettest, Christchurch the driest and sunniest, and Dunedin the coolest.

Rainfall

In contrast, rainfall was less than 50 percent (half) of normal in eastern Bay of Plenty, and inland South Canterbury, and also below normal in Western Bay of Plenty, north Taranaki, Manawatu, Buller, along the Kaikoura coast, and inland areas of Southland and Otago. In contrast, rainfall was much wetter than usual in Northland, many locations recording 200 percent (twice) or more of normal December rainfall due to an unsettled start to the month. Rainfall was also above normal in Coromandel, Gisborne, and Hawke’s Bay.

Temperature

Mean temperatures were at least 0.5 ºC above average in most northern and western regions of New Zealand, as well as Southland and much of Otago, and at least 1.0 ºC above average in parts of Auckland, Waikato, Taranaki, Manawatu, Buller, Westland, Fiordland, Nelson, and Central Otago. Temperatures were near average in the east from Gisborne to Dunedin, as well as eastern Northland and Wellington.

Sunshine

Sunshine hours were at least 120 percent of normal in Southland and Otago. However, cloudy skies prevailed over the northern half of the North Island. Sunshine hours were also below normal in Gisborne, Wellington, Marlborough, and Nelson.

Full report

• Full details of the December 2007 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.