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 11^th and 12^th and also at Wreys Bush (Southland) on the 11^th, to a sweltering high of 26.5°C, recorded in Napier on the 26^th during warm north westerlies.
• Heavy rainfall occurred over the central North Island on the 1^st, and in Golden Bay on the 3^rd and 13^th. A depression produced high rainfall over the North Island from the 27^th-28^th, 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 18^th at South West Cape.
• Cold southeasterlies brought significant snowfall settling down to 400 metres in Canterbury on the 28^th, 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 30^th, b: missing 30^th

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 11^th and 12^th, and also at Wreys Bush (Southland) on the 11^th. Waimate recorded –4.9°C on the 1^st, (the 2^nd 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 26^th (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 1^st. Other heavy rainfall events occurred in Golden Bay on the 3^rd and 13^th, with at about 70mm.
• Gale force Northwesterlies buffeted Manawatu, Wellington, Kapiti, Wairarapa, Marlborough, Canterbury, Otago, and Southland on the 18^th, 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 25^th, 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 1^st. Other heavy rainfall events occurred in Golden Bay on the 3^rd and 13^th, with at about 70mm.
• A depression produced high rainfall over the North Island from the 27^th-28^th, 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 27^th. 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 28^th and 29^th. 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 28^th.
• Cold southeasterlies affected Canterbury on the 28^th, 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 [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.