September 2003

Wednesday, 1 October 2003

Rainfall: Extremely high in many areas, especially in Taranaki, King Country, Wanganui, Gisborne, Hawke’s Bay, Wairarapa, Kaikoura, Canterbury and north Otago; dry in Dunedin and South Otago

Temperatures: Above average temperatures over much of the North Island, especially Northland, Auckland, Bay of Plenty, Gisborne and Hawke’s Bay; below average in the southwest of the South Island especially south Westland, Fiordland and Central Otago

Sunshine: Below average in Northland, Gisborne, and Central Otago

September was a month of extremes. Stormy and unsettled conditions characterized the month throughout the country. Taranaki, King Country, Wanganui, and eastern regions from Gisborne to north Otago. Despite this, soil moisture deficits are increasing in eastern Otago. It was warmer than usual over much of the North Island and colder than normal in the southwest of the South Island. Sunshine hours were below average in Northland, Gisborne and Central Otago. The September climate patterns were associated with very many more deep depressions (‘lows’) than usual in the South Tasman Sea, with much below average pressures over New Zealand. A number of depressions also tracked across the North Island, where westerly winds were very frequent. Mean sea level pressures were more than 10hPa below normal over much of New Zealand, and the lowest on record for September in New Plymouth and Gisborne where records commenced in 1944 and 1962 respectively.

Highlight

  • September 2003 air temperatures ranged from a low of –5.2°C, recorded at Ranfurly on the 11th and 12th and also at Wreys Bush (Southland) on the 11th, to a sweltering high of 26.5°C, recorded in Napier on the 26th during warm north westerlies.
  • Heavy rainfall occurred over the central North Island on the 1st, and in Golden Bay on the 3rd and 13th. A depression produced high rainfall over the North Island from the 27th-28th, with the heaviest falls in Taranaki, Tongariro, and the Gisborne high-country.
  • There were frequent days of gales from the westerly sector, some damaging, with a top wind gust of 176 km/hr on the 18th at South West Cape.
  • Cold southeasterlies brought significant snowfall settling down to 400 metres in Canterbury on the 28th, resulting in some stock losses.
  • Dunedin was the driest of the four main centres, and Christchurch the sunniest. September rainfall was above average in Auckland, Wellington, and Christchurch, and near average in Dunedin. Mean temperatures were near average in Dunedin and above average in the other three centres. Sunshine hours were near average in all four centres.

Rainfall: It was unsettled with above average in most regions, and 200 percent (double) or more of average in many eastern regions from Gisborne to north Otago, as well as Taranaki, King Country, and Wanganui. Contrasting below average rainfall occurred in eastern Southland and parts of Otago, with totals 75 percent (three quarters) or less of average. Rainfall was near average in Northland and coastal areas of Bay of Plenty.

Temperatures: Mean temperatures were above average throughout much of the North Island, and from coastal Marlborough to Canterbury. It was very warm in Gisborne and Hawke’s Bay where temperatures were about 1.5°C above average. Cooler than usual conditions prevailed in inland south Canterbury, eastern Otago, and Southland, and temperatures were at least 1.0°C below average in south Westland, Central Otago and the Southern Lakes. The September national average temperature of 10.6°C was 0.3°C above normal.

Sunshine: Sunshine totals were below average in Northland, Gisborne, and West Otago, and near normal in most other regions.

Extremely high rainfall in many regions

September was unsettled with rainfall at least 150 percent (one and a half) of average in most regions. Totals were at least 200 percent (double) of average in most eastern regions from Gisborne to north Otago, as well as Taranaki, King Country, and Wanganui. Contrasting below average rainfall occurred in eastern Southland and parts Otago, with totals 75 percent (three quarters) or less of average, and soil moisture deficits higher than normal. Rainfall was near average in Northland and coastal areas of Bay of Plenty.

Locations with near- or record high September rainfall

Location September rainfall (mm) Percentage Of normal Year Records began Comments
Taupo Airport 143 191 1976 Highest
Motu 494 254 1991 Highest
Gisborne Airport 183 195 1905 Well above normal
Napier Airport 148 211 1950 Equal highest
Napier, Nelson Park 136 204 1870 Well above normal
Mahia 163 227 1991 Highest
Castlepoint 185 233 1902 Well above normal
East Taratahi 173 194 1972 2nd highest
Taumarunui 286a 204 1913 Highest
New Plymouth Air. 238 207 1944 2nd highest
Lower Retaruke 285b 205 1966 Highest
Normanby 191 193 1986 Highest
Waiouru 191 193 1950 Highest
Ohakune 304 221 1993 Highest
Wanganui 145 219 1890 Highest
Palmerston North Air. 149 182 1943 3rd highest
Palmerston North 161 201 1928 3rd highest
Wellington Airport 173 212 1960 2nd highest
Blenheim Research 95 213 1930 Well above normal
Hanmer Forest 280 291 1905 Well above normal
Kaikoura 153 260 1949 Well above normal
Rangiora 119 246 1965 3rd highest
Darfield 112 214 1920 Well above normal
Christchurch Airport 86 209 1944 Well above normal
Lincoln 88 219 1881 Well above normal
Winchmore 131 280 1947 3rd highest
Timaru Airport 89 260 1956 3rd highest
Oamaru Airport 82 329 1941 2nd highest

a: missing 30th, b: missing 30th

Warmer over much of the North Island, colder in the southwest of the South Island

Mean temperatures were at least 0.5°C above average throughout much of the North Island, and from coastal Marlborough to Canterbury. Temperatures were at least 1.0°C above average in eastern Northland, Coromandel, and Bay of Plenty, and about 1.5°C above average in Gisborne and Hawke’s Bay. However, they were more than 0.5°C below average in inland south Canterbury, eastern Otago, and Southland, and at least 1.0°C below average in south Westland, Central Otago and the Southern Lakes. Temperatures were near average in Manawatu, Nelson, Buller, and north Westland.

Locations with near- or record mean September temperatures

Location Mean temperature Departure from average (°C) Records began Comments
Whangarei Airport 14.2 +1.3 1967 Highest
Tauranga Airport 13.3 +1.4 1913 3rd highest
Whakatane Airport 12.8 +1.6 1975 2nd highest
Gisborne Airport 13.3 +1.6 1905 3rd equal highest
Napier Airport 13.2 +1.7 1974 2nd highest

Below average sunshine in Northland, Gisborne and central Otago

Sunshine totals were below average (less than 90 percent of normal) in Northland, Gisborne, and Central Otago. They were near normal in most other regions.

Locations with record low September sunshine

Location September sunshine (hours) Percentage of normal Year Records began Comments
Queenstown 116 73 1930 2nd Lowest

September climate in the four main centres

Of the four main centres, Dunedin was the driest, with 44 mm. September rainfall was above average in the other main centres. Mean temperatures were below average in Dunedin and above average in the other three centres. Sunshine hours were near average in all four centres, of which Christchurch was the sunniest.

  Auckland Wellington Christchurch Dunedin
September mean temp.
(°C)
13.3 10.8 10.3 8.9
Dep. from normal
(°C)
+0.8 +0.3 +0.3 –0.4
  Above average Above average Above average Below average

September rainfall (mm) 180 161 86b 44c
% of normal 162 155 209 99
  Above average Above average Well above average Near average

September sunshine (hours) 154d 148 166 137a
% of normal 94 95 104 105
  Near average Near average Near average Near average

a: Mt Albert, b: Christchurch Airport, c: Dunedin Airport, d: Whenuapai

Highlights and extreme events

  • The lowest air temperature for September 2003 was –5.2°C, recorded at Ranfurly on the 11th and 12th, and also at Wreys Bush (Southland) on the 11th. Waimate recorded –4.9°C on the 1st, (the 2nd lowest on recorded there in September, records began in 1908).
  • The highest air temperature for September 2003 was 26.5°C, recorded in Napier on the 26th (the highest there in September since 26.7°C in 1955).
  • Near record low grass minimum September temperatures were recorded at:
    Location Grass min. (°C) Date Records began Comments
    Ettrick -11.0 12th 1985 2nd lowest
  • Heavy rainfall totalling at least 70 mm occurred over the central North Island, including Taranaki on the 1st. Other heavy rainfall events occurred in Golden Bay on the 3rd and 13th, with at about 70mm.
  • Gale force Northwesterlies buffeted Manawatu, Wellington, Kapiti, Wairarapa, Marlborough, Canterbury, Otago, and Southland on the 18th, with winds gusting to 126 km/h at Paraparaumu Airport, 141 km/h at Tiwai Point, 169 km/h at Castlepoint, and 176 km/h at South West Cape. The winds lifted some roofs, smashed windows and resulted in fallen trees in parts of Wairarapa and Wellington. Airport hangars at Paraparaumu airport also suffered damage. In the Wairarapa, six trucks were blown over by the wind, and power lines damaged.
  • Gale force north-westerlies buffeted Wellington, Kapiti, Hawke’s Bay, Marlborough, Canterbury, Otago, and Southland on the 25th, with winds gusting to 122 km/h at Mt. Cook Village, and 135 km/h at Southwest Cape.
  • Heavy rainfall totalling at least 70 mm occurred over the central North Island, including Taranaki on the 1st. Other heavy rainfall events occurred in Golden Bay on the 3rd and 13th, with at about 70mm.
  • A depression produced high rainfall over the North Island from the 27th-28th, with 1-day falls totalling at least 70 mm in Taranaki, Tongariro, and the Gisborne high-country. Parts of Taranaki recorded more than 100mm of rainfall in the 12 hours to noon on the 27th. There were numerous reports of surface flooding and heavy rainfall throughout the North Island, which contributed to isolated landslides and treacherous driving conditions for many motorists. The same depression produced westerly gales and close to 100 km/h wind gusts in Auckland and parts of Bay of Plenty on the 28th and 29th. Some power lines were blown down. In Whangamata (Coromandel), a boy suffered burns, damage to sight and hearing loss after being struck by lightning on the 28th.
  • Cold southeasterlies affected Canterbury on the 28th, with snow depths of about 30cm settling down to 400m. Some lambs died due to exposure. Snowfall was up to 50cm deep on the Lewis, Porters, and Burkes Pass roads.

For further information, please contact:

Dr Jim Salinger – Principal Scientist, Climate
NIWA National Climate Centre – Auckland
Phone +64 9 375 2053
j.salinger@niwa.co.nz

Stuart Burgess – Climatologist
NIWA National Climate Centre – Wellington
Phone +64 4 386 0569
s.burgess@niwa.co.nz

Geoff Baird – Communications Manager
Phone +64 4 386 0543
g.baird@niwa.co.nz

Acknowledgement of NIWA as the source is required.