May 2003

Sunday, 1 June 2003

Sunny with well below average rainfall in Waikato, Wanganui, Manawatu, Wellington, Wairarapa, Westland, Fiordland, Marlborough, Alpine areas, Otago and Southland

Significant soil moisture deficits persist in Wanganui, Manawatu, Horowhenua, South Canterbury and Central Otago

Above average rainfall in Bay of Islands, Coromandel, and north and central Canterbury

Warmer in parts of Auckland, Bay of Plenty, Waikato, and Buller, but colder in Wellington, Wairarapa, Marlborough, Canterbury, Otago and Southland

May was much warmer than average over all of New Zealand, and rainfall was well above normal in northern parts of Northland. However, average or below average rainfall occurred in many areas, and soils remained dry in Marlborough and large parts of Otago. The month’s climate pattern was dominated by more frequent anticyclones (‘highs’) to the east of the North Island and southwest of Tasmania. Between these systems, more frequent northeasterlies occurred over the northern half of the North Island and westerlies over southern New Zealand.

Highlights:

• May 2003 temperatures ranged from of low of –7.0°C, recorded at Fairlie on the 19th, to a high of 26.2°C, recorded at Christchurch Gardens on the 20th.
• Heavy rainfall with northerlies occurred in the Southern Alps on the 1st, totalling about 180 mm at nearby Mt Cook Village and Arthur’s Pass. The same trough produced significant rainfall (at least 75 mm) in and north of the Bay of Islands on the 2nd, with 110 mm recorded at Kaitaia Airport. Another northerly event occurred later in the month, with rainfall totals of at least 75 mm (and almost 100 mm in parts of the Bay of Islands) affected Northland, King Country, and Tongariro on the 21st. Easterlies resulted in rainfall totalling almost 100 mm in parts of Hawke’s Bay over 23–24 May.

Temperatures

Mean temperatures were above average throughout New Zealand, especially in south Auckland, Bay of Plenty, Gisborne, Buller, Nelson, and Marlborough where they were about 1.5°C above normal in some areas. The May national average temperature of 11.6°C was 1.1°C above normal, the warmest since May 2000.

Rainfall

Rainfall was above average throughout northern Northland, King Country, Tongariro–Taupo, Hawkes Bay and the west coast of the South Island, and more than 200 percent (double) of average at Cape Reinga in the far north. However, totals were less than 33 percent (a third) of average in parts of southern Wairarapa, north Canterbury, coastal Otago and inland Southland.

Soil moisture

Significant soil moisture deficits continued in Marlborough, north and Central Otago. However, more regular rainfall brought relief to other eastern South Island regions, as well as the southwest of the North Island.

Sunshine

Sunshine hours were well above average in coastal areas of both Southland and Otago and in Wellington.

Noticeably above average temperatures throughout much of the North Island and the northern half of the South Island

Mean temperatures were at least 1.0°C above average in eastern Northland, south Auckland, Waikato, Coromandel, Bay of Plenty, Taranaki, the central North Island Plateau, Wellington, southern Wairarapa, Buller, Nelson, Marlborough, north Westland and north Canterbury, and 0.5 to 0.9°C above average throughout the remainder of New Zealand.

Near or record high mean May temperatures were recorded at:

Location	Mean temperature	Departure (°C)	Records began	Comments
Whangarei Airport	15.2	+1.3	1968	2nd highest
Auckland, Mangere	15.0	+1.5	1959	3rd highest
Tauranga Airport	14.0	+1.6	1913	Well above average
Gisborne Airport	13.6	+1.6	1905	Well above average
Paraparaumu Airport	12.6	+1.4	1953	Well above average
Farewell Spit	13.7	+1.9	1971	Highest
Nelson Airport	11.7	+1.8	1943	2nd equal highest
Hanmer Forest	9.6	+2.2	1906	2nd equal highest
Raoul Island	19.8	+1.1	1940	Well above average

Extraordinary high mean daily maximum May temperatures were recorded at:

Location	Mean daily maximum temperature	Departure (°C)	Records began	Comments
Hanmer Forest	16.6	+3.4	1906	Highest

Above average rainfall in Northland and across the central North Island, average or below average rainfall elsewhere

Rainfall was 150 percent or more of average throughout much of northern Northland, and at least 125 percent of average in King Country, Tongaririo–Taupo, Hawkes Bay and the west coast of the South Island. Rainfall totals ranged from about 25 percent (a quarter) to 75 percent (three quarters) of average in much of southern Wairarapa, north Canterbury, Otago and inland Southland, and 50 percent (half) to 75 percent (three quarters) of average in Nelson and Marlborough. Rainfall was near average elsewhere.

Well above average May rainfall was recorded at:

Location	May rainfall (mm)	Percentage of normal year	Records began	Comments
Cape Reinga	208	237	1920	Well above average

Near or record low May rainfall was recorded at:

Location	May rainfall (mm)	Percentage of normal	Records began	Comments
Rangiora	13	24	1965	2nd lowest
Dunedin Airport	23	38	1963	3rd lowest

Much sunnier than average in coastal areas of both Southland and Otago

Sunshine and solar radiation totals were well above average (at least 120 percent of normal) in coastal areas of both Southland and Otago, and in Wellington. Near normal sunshine totals were recorded in most other regions.

Well above average May sunshine hours were recorded at:

Location	May sunshine (hours)	Percentage of normal	Records began	Comments
Dunedin, Musselburgh	124	129	1948	Well above average

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.