August 2002

Sunday 1 September 2002

Average or below average rainfall in many regions
Wet in the southwest of the South Island
Mild overall in most regions
Sunny in the south and east of the North Island and northwest of the South Island

Much drier conditions than normal occurred in the northeast of the South Island in August for the second consecutive month accompanied by unsettled and wetter than normal conditions in the southwest of the South Island. The month was milder than usual, despite a cold wintry outburst during the last week.

Frequent southwesterlies resulted in rainfall that was less than 50 percent (half) of average from Marlborough to mid Canterbury, as well as in parts of Bay of Plenty. It was also drier than normal in much of Nelson, Buller, south Canterbury, inland Wairarapa, and parts of Northland and Auckland. Above average rainfall occurred in Southland, Fiordland, the Southern Lakes region, and parts of Central Otago. Rainfall was also above average in south Taranaki, Wanganui and on the Kapiti Coast.

August was milder than usual in most regions. However, temperatures were near average in Westland, the central North Island, parts of Northland and scattered areas of Central Otago and inland Southland. The national average mean temperature of 9.2°C was 0.5°C above normal.

Sunshine totals were near average in many areas, but Gisborne, Hawke’s Bay and Wellington were sunnier than normal. Lower than normal sunshine totals were recorded in Wanganui, coastal Southland and Central Otago.

August’s climate pattern was dominated by more frequent southwesterlies than average over New Zealand, with below average pressures about and east of the Chatham Islands and more frequent anticyclones south of Australia.

Wet in the southwest of the South Island
Average or below average rainfall in many other regions

For the second consecutive month rainfall was below average from Nelson to Canterbury. Less than 50 percent of average rainfall occurred from Marlborough to mid Canterbury, as well as in parts of Bay of Plenty. Rainfall was also below normal in much of Nelson, Buller, south Canterbury, inland Wairarapa, and parts of Northland and Auckland, being less than 75 percent of average. Other regions experienced near normal rainfall. However, the month was unsettled with rainfall totals at least 125 percent of average throughout Southland, Fiordland, Southern Lakes, and in parts of Central Otago. Rainfall was also at least 125 percent of average in south Taranaki, Wanganui and the Kapiti Coast.

Mild overall in most regions

Mean temperatures ranged from 0.5 to 1.0°C above normal in most regions. However, they were near average in Westland, the central North Island, parts of Northland and scattered areas of Central Otago and inland Southland. Near or record high mean August temperatures were recorded at:

Location	Mean temperature	Departure (°C)	Records began	Comments
Pukekohe	11.8	+1.2	1970	Highest
Dunedin, Musselburgh	8.7	+1.1	1947	2nd equal highest

Daytime maxima were between 1.0 and 1.5°C above normal in Nelson, Marlborough and Canterbury.

Sunny in the south and east of the North Island and the northwest of the South Island

Sunshine and solar radiation totals were near average in many areas. However, they were at least 110 percent of average in Gisborne, Hawke’s Bay and Wellington, nelson and north Westland. Totals were less than 90 percent of average in Wanganui, coastal Southland and Central Otago.

Highlights

Extreme temperatures

• Very high August temperatures occurred on the 12th, as warm northwesterlies fanned the east coast of the South Island. This pushed temperatures up to an unofficial 24.8°C at Waipara in North Canterbury, almost a New Zealand record for the month of August. Other official high temperatures that day were:

  Location	Maximum temperature °C	Comments
  Darfield	23.3	Highest. Records began in 1939.
  Christchurch Gardens	22.8	2nd highest, 23.2°C in 1970. Records began in 1864.
  Christchurch Airport	22.2	2nd highest, 22.8°C in 1970. Records began in 1954.
  Lincoln	21.6	4th highest (record is 22.2°C in 1893 and 1970). Records began in 1881.
  Rangiora	21.6	Highest since 21.7°C in 1995.
  Woodbury	23.0	Highest. Records began in 1993.

  The highest August New Zealand temperature is 24.9°C recorded at Cheviot on 28 August 1994. The North Island August record is 24.7°C at Whakatane on 11 August 1978.

• Other extremely high temperatures (on the 4th of August) were:

  Location	Maximum temperature °C	Comments
  Whangarei Airport	20.8	Highest. Records began in 1939.
  Whakatu	22.0	2nd equal highest. Records began in 1983.

• The lowest air temperature for the month was –8.5°C, recorded at Hanmer Forest on the 1st. The lowest August air temperature on record there is -12.3°C.

High rainfall and flooding

• High rainfall totals, up to 75 mm, were recorded at sites in Gisborne on the 6th, resulting in surface flooding. Much higher rainfall occurred in the hill country to the north, where roads were closed and schools finished early.

Snowfall and gale force winds

• Snowfall overnight on the 18th resulted in the closure of the North Island’s Desert Road. The same weather system produced gale force southerlies and high (at least 4 metre) seas in Cook Strait, resulting in the cancellation of a number of fast-ferry services on the 18th and 19th. Conventional ferry services were also hampered. A rail wagon on the Aratere was tipped over by a freak wave. Southerly winds gusted to 124 km/h at Brothers Island on the 19th .

• Snowfall also occurred on the 26th in Queenstown-Southern Lakes district, Central Otago, parts of Southland, the hill country around Dunedin, and to low levels on the Port Hills in Canterbury. Waves as high as 12 metres were reported around Banks Peninsula. Southerly gales damaged boats in Lyttelton Harbour. Waves as high as 10 metres occurred in Cook Strait on the 27th, while ice closed the North Island’s Desert Road. On the 26th, mean wind speeds reached 100 km/h from the southwest Taiaroa Head and 98 km/h at Le Bons Bay.

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.