January 2006

• Temperature: Well below average in the west of the South Island; above average in the east of the North Island; Central Otago heat-wave toward the end of the month
• Rainfall: Well above normal in Northland, inland Bay of Plenty, Taupo, and Southland; well below normal in Horowhenua
• Soil moisture: Significant deficits in the east of the South Island, and southwest of the North Island
• Sunshine: Normal or above throughout New Zealand

Western South Island temperatures plummeted in January, especially noticeable after one of the warmest Decembers on record. Mean January temperatures were as much as 1.5 °C below average in parts of Westland and Fiordland. They were also below average in several other southern and western South Island regions. Temperatures however, were above average in the east of the North Island. The national average temperature was 17.0 °C, the same as the 1971-2000 normal. A heat-wave occurred in Central Otago toward the end of the month, Alexandra recording maximum temperatures of 36 °C for three consecutive days from the 27-29th, unheard of in their historical record, which commenced in 1930. A mixed pattern of rainfall occurred over New Zealand in January, with relatively high totals in parts of Northland, inland Bay of Plenty, Taupo, and Southland, and comparatively low totals in Horowhenua. Significant soil moisture deficits developed in northern and eastern regions of both Islands until a depression of tropical origin produced substantial rainfall in those regions during 24-25 January. However, high rainfall did not affect the southern and eastern South Island, and significant soil moisture deficits persisted in parts of Canterbury and Central Otago, as well as Manawatu, Wellington, and Wairarapa. Sunshine hours were normal or above normal throughout New Zealand. January mean sea level pressures were well below average in the Southern Ocean with frequent troughs of low pressure influencing the South Island. Mean sea level pressures were above average in the north Tasman Sea. These patterns resulted in more frequent westerlies than average over New Zealand.

Other Highlights

• The highest temperature recorded during January 2006 was 36.0 °C recorded at Alexandra on the 27th, 28th, and 29th; the lowest temperature for the month was -1.2 °C at Ranfurly on the 19th.
• The highest wind gusts for the month were 165 km/h from the northwest, occurring at Kaukau Top between the 2nd and 4th of January, while gales buffeted Wellington city.
• Substantial rainfall occurred in Northland, Coromandel, Waikato, Bay of Plenty, and Nelson over 24-25 January, Rotorua recorded 140 mm over the 24 hour period to 9am on the 25th, and as much as 260 mm was noted in just 14 hours on the Coromandel Peninsula. Gale force easterlies affected Auckland, and Coromandel, with about 7000 homes on the Coromandel Peninsula losing power due to fallen branches or trees. A truck was overturned, and there were dozens of road accidents in Auckland during the hazardous conditions. High rainfall also occurred in the Rotorua/Taupo districts on the 28th, with a severe thunderstorm, and surface flooding.
• Of the four main centres Christchurch was the driest, and Auckland the wettest. Auckland had near normal rainfall, temperature, and sunshine. Wellington was drier and sunnier than normal, Christchurch was drier than normal, and Dunedin was sunnier than normal.

Temperature

Mean temperatures were 1.0 to 1.5 °C below average throughout much of Buller, Westland and Fiordland. They were also below average in parts of the eastern South Island from south Canterbury to Southland.

Mean temperatures were above average in the east of the North Island from Gisborne to Wairarapa.

Rainfall

Rainfall was almost 200 percent (twice) of normal in parts of Northland, inland Bay of Plenty, Taupo, and Southland. Rainfall was also above normal in Waikato, Coromandel, western Bay of Plenty, Nelson Lakes, south Westland, Fiordland, Marlborough, south Canterbury, and Southern Lakes. Milford Sound’s rainfall exceeded 1000 mm for the month, almost 900 mm occurring within the first two weeks. Totals were 50 percent (half) or less of normal in Horowhenua, and 75 percent (three quarters) or less of normal in Kapiti, along the Kaikoura Coast, north Canterbury, and in Central Otago.

Sunshine

Sunshine hours were almost 120 percent of normal in Westland and coastal Otago. They were also above normal in Wellington, Marlborough, inland south Canterbury, and Southland.

Full report

• Full details of the January 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.