July 2003

Friday, 1 August 2003

Sunshine: More than normal sunshine across the country, except for Auckland

Rainfall: Below average in most regions, especially Bay of Plenty, Marlborough and Nelson; wet along the Southland coast

Temperatures: Below average in most places and frostier than normal in many areas

July was colder, sunnier, and more settled and frosty than average, with well below average rainfall in most areas, especially parts of Marlborough and Nelson where July was the driest in more than 60 years of measurement. A severe snowstorm swept the country over 4–5 July. The July climate patterns were associated with more anticyclones (‘highs’) than average over New Zealand and in the Tasman Sea. These produced frequent days of light winds and clear settled conditions with cold nights.

Highlights:

• July 2003 temperatures ranged from a low of –14.8°C, recorded at Tekapo on the 13th, to a high of 18.3°C, recorded at Hanmer Forest on the 16th. This was Tekapo’s 2nd equal lowest July air temperature on record (measurements commenced in 1925).
• A very cold southerly outbreak brought significant snowfall to sea level in the eastern South Island on 4–5 July, with heavy snowfall settling down to 300–500 m in the central and eastern North Island on the 5th. Severe overnight ground frosts followed, especially in the South Island.
• The third week of July was very calm and anticyclonic with five to seven consecutive days of severe frosts in many inland areas.
• Rainfall and days with strong winds were below average in all the four main centres. Temperatures were below average in Christchurch, and near average in Auckland, Wellington and Dunedin. Sunshine hours were above average in Wellington, Christchurch and Dunedin. Totals were much lower than usual in Auckland.

Rainfall

It was rather settled, with rainfall less than 50 percent (half) of average in parts of Bay of Plenty, King Country, Taupo, the central North Island Plateau, Hawke’s Bay, Wellington, the South Island West Coast, Marlborough, Nelson, and coastal areas of both south Canterbury and Otago. Rainfall was also below average in most other regions. Totals were above average along the Southland coast.

Temperatures

Mean and minimum temperatures were below average over much of New Zealand. However, mean temperatures were above average in inland and Central Otago. The July national average temperature of 7.3°C was 0.4°C below normal. There were more ground and air frosts than normal in many areas, especially in the south and west of the North Island, including the Central Plateau, and parts of the north and east of the South Island. The frostiest periods, often with severe ground frost, occurred on July 6, 7, 12–14 and 20–26. Severe ground frost (–6.0°C or lower) occurred somewhere in New Zealand on most days of the month. High winds were largely absent.

Sunshine

Sunshine hours were above average in most regions, especially from Wairarapa to Otago, and in central regions from Wanganui to Westland, including Nelson and Wellington. Totals were well below average in Auckland.

Below average rainfall in most regions

Rainfall was less than 50 percent (half) of average in Bay of Plenty, King Country, Taupo, the central North Island Plateau, Hawke’s Bay, Wellington, the South Island West Coast, Marlborough, Nelson, and coastal areas of both south Canterbury and Otago. Totals were less than 75 percent (three-quarters) of average in most other regions.

Near or record low July rainfall was recorded at:

Location	July rainfall (mm)	Percentage of normal	Records began	Comments
Kawerau	30	19	1954	Lowest
Rotorua Airport	23	18	1964	Lowest
Taupo Airport	23	27	1976	Lowest
Turangi	33	22	1968	2nd lowest
Whakatu	33	33	1983	3rd lowest
Hokitika Airport	87	38	1964	3rd lowest
Motueka, Riwaka	21	13	1943	3rd lowest
Nelson Airport	9	10	1941	2nd lowest
Nelson, Appleby	9	9	1932	3rd equal lowest
Blenheim Airport	11	15	1941	Lowest
Cape Campbell	20	26	1988	2nd lowest
Timaru Airport	8	17	1957	2nd equal lowest

Rainfall was at least 120 percent of average along the Southland coast, and near average in much of Northalnd, Manawatu, Horowhenua, Southern Lakes, Central Otago, and inland Southland.

Below average temperatures in most places

Mean temperatures were at least 0.5°C below average throughout much of the North Island and northern half of the South Island, scattered areas being 1.0 to 1.5°C below average. They were about 0.5°C above average in inland and Central Otago.

Mean daily maximum temperatures were about 2.0°C above average in western and Central Otago. Mean daily minimum temperatures were 1.0 to 2.0°C below average throughout much of New Zealand.

Near or record low mean July temperatures were recorded at:

Location	Mean temperature	Departure from average (°C)	Records began	Comments
Whakatu	6.6	–1.8	1983	Lowest
East Taratahi	6.1	–1.3	1972	3rd lowest

Near or record low mean daily minimum July temperatures were recorded at:

Location	Mean temperature	Departure (°C)	Records began	Comments
East Taratahi	0.0	–2.7	1972	2nd lowest
Whakatu	0.9	–2.2	1983	Lowest
Westport Airport	3.0	–1.5	1937	3rd equal lowest
Blenheim Airport	–0.3	–1.7	1941	3rd equal lowest
Christchurch Airport	–0.9	–1.7	1954	3rd equal lowest

The frequent anticyclonic conditions produced clear nights with more days of frost, especially in the south and west of the North Island, including the Central Plateau, Nelson, and Canterbury. Some locations in these regions experienced air and ground frost on least 5 to 10 days more than average, with some severe occurrences. Some statistics on days of frost follow:

Well above average numbers of days with ground frost were recorded at:

Location	Days with ground frost	Departure from normal	Records began	Comments
Waiouru	25	+8	1960	Highest
Levin	22	+10	1921	2nd equal highest, most since July 1971
Paraparaumu Airport	19	+8	1953	Highest
Rangiora	25	+8	1965	Highest
Christchurch Airport	25	+6	1954	2nd equal highest
Christchurch Gardens	27	+8	1864	2nd equal highest. Highest since 1952
Balclutha, Finegand	25	+8	1964	Highest

Sunny in most regions

Sunshine totals were well above average (at least 120 percent of normal) in many eastern regions from Wairarapa to Otago, and in central regions from Wanganui to Westland, including Nelson and Wellington, and at least 110 percent of normal in most other regions. Well below normal sunshine occurred in Auckland.

Well above average July sunshine hours were recorded at:

Location	July sunshine (hours)	Percentage of normal	Records began	Comments
Paraparaumu Airport	162*	133	1953	4th highest
Wellington, Kelburn	153	139	1928	4th highest
Hokitika Airport	148	123	1964	Well above average
Nelson Airport	195	126	1949	3rd highest
Dunedin, Musselburgh	134	141	1948	4th highest

* missing 28 July

Fewer windy days

There were fewer days with strong winds than average in July over much of New Zealand. This was particularly noticeable during the last few weeks.

Some wind gust statistics are:

Location	July days with wind gusts ≥ 60 km/h	Departure from average
Auckland Airport	2	–5
Hamilton Airport	0	–2
Wellington, Kelburn	12	–4
Nelson Airport	0	–2
Christchurch Airport	2	–1
Dunedin Airport	5	+1

July climate in the four main centres

July rainfall was below average in all the main centres. Dunedin was the driest centre, receiving only 27 mm of rain. Mean temperatures were below average in Christchurch, and near average in the other three centres. Wellington was the sunniest. Sunshine hours were also above average in Christchurch and Dunedin. Auckland received much less sunshine than normal.

	Auckland*	Wellington	Christchurch	Dunedin
July mean temp. (°C)	10.3	8.4	5.9	6.4
Dep. from normal (°C)	–0.2	–0.1	–0.4	–0.1
	Near average	Near average	Below average	Near average
July rainfall (mm)	113	64	47	27
% of normal	81	45	61	39
	Below average	Below average	Below average	Well below average
July sunshine (hours)	86	153	140	134
% of normal	66	139	115	141
	Well below average	Well above average	Above average	Well above average

*Mt Albert

Highlights and extreme events

• July 2003 temperatures ranged from a high of 18.3°C, recorded at Hanmer Forest on the 16th, to a low of –14.8°C, recorded at Tekapo on the 13th. This was Tekapo’s 2nd equal lowest July air temperature on record (measurements commenced in 1925).
• A very cold southerly outbreak brought significant snowfall to sea level in the eastern South Island over the 4th and 5th of July, with heavy snowfall settling down to 300–500 m in the central and eastern North Island on the 5th. Snow flurries occurred to sea level in parts of the western north Island, and also in the east as far north as Napier. Snow settled to depths to 50 cm in the western Hawke’s Bay high-country, 30 cm in the Gisborne high-country, 30 cm in the Manawatu about and east of the Gorge, 35 cm on the Rimutaka Summit Road north of Wellington, 20–35 cm in inland Canterbury, and 10 cm in some inland areas of south Taranaki and Southland, with a few centimetres to sea level in many eastern South Island districts. Snow covered roads were treacherous, leaving most high-country roads closed. Numerous motorists and travellers were stranded, especially on the Desert Road (where some truck drivers stayed overnight in their cabs) and at Norsewood. Power was cut to more than 10,000 homes in the central and eastern North Island at the height of the storm, and many rural schools in both islands were closed. Dunedin, Invercargill and Queenstown airports were all closed for a period during the event, due to icy runways. South Island maximum temperatures ranged from just 1 to 5°C in many eastern areas south of Kaikoura on the 4th and 5th.
• Severe overnight ground frosts occurred in the fine weather that followed, especially in the South Island.
• Severe frosts resulted in near or record low minimum July air temperatures at:

Location	Min. (°C)	Date	Records began	Comments
East Taratahi	–5.9	7	1972	Lowest
Ranfurly	–11.6	5	1975*	Lowest
Dunedin Airport	–8.6	13	1963	Lowest
Lauder	–9.4	5	1982	2nd equal lowest

*Incomplete record

• Near or record low grass minimum July temperatures were recorded at:

Location	Grass min. (°C)	Date	Records began	Comments
East Taratahi	–9.3	14	1972	Lowest
Whakatu	–9.0	7	1983	Lowest
Rangiora	–10.8	13	1965	2nd lowest
Christchurch Airport	–10.3/–11.5	7/13	1954	Lowest

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.