NZ weather summary July 1983

[Rwood]

July 1983: July was a cool month with below average rainfall over the North Island and more rain than usual over the South Island. South-easterly winds were much more frequent than usual over New Zealand, resulting in an unusual rainfall and sunshine distribution. A warm and very moist northerly airstream covering New Zealand between the 8th and 10th brought rain to much of the country with widespread and heavy falls over northern parts of the South Island on the 9th. Major flooding occurred in Marlborough and golden Bay, resulting in heavy stock and property losses. Several communities were isolated, with some 500 people having to evacuate their homes.

Rainfall: North Island rainfalls were generally below normal, with many areas having very little rain. Less than 50% of the July average was recorded over most of the island, while parts of the Waikato and Bay of Plenty received less than 30% of the usual totals. Hamilton (31 mm) and Whakatane (27 mm) had record lows for the month, while Tauranga (22 mm) recorded its lowest July total since 1902. The far north, and eastern areas from Gisborne to Cook Strait recorded rainfalls close to or slightly above normal, Wellington getting 124% of the usual total. Over much of the South Island rainfalls were above normal, although parts of Southland, and some northern areas, despite the flood period, received considerably less than usual. Lake Rotoiti’s 45 mm was only 29% of the normal. Heavy snow fell over Otago on the 1st and over Canterbury on the 2nd. Some 40,000 sheep were rescued from the snow in the upper Clutha and Waitaki valleys and drifts of snow on Banks Peninsula were up to 3 metres deep. Snow and ice in this period closed several roads in Otago, and the road and railway across Arthurs Pass.

Some totals (mm): Wainuiomata 380, Greymouth 298, Riwaka 249, Rai Valley 290, Lake Hawea 113; Leigh 27, Albert Park 41, New Plymouth Aero 61, Ohakea 26, Wanganui 16, Cape Campbell 39, Invercargill 49, Campbell Is 57.

Temperatures: Average temperatures were close to normal over central and eastern areas of New Zealand, while much of the country experienced temperatures between 0.5C and 1.0C colder than usual. A few areas, notably coastal parts of Southland and Otago, had temperatures up to 1C warmer than normal. The first 6 days were cold with minima around 6C below average in many places. Ice formed on Lyttelton Harbour on the morning of the 6th; the first occurrence for the outer Harbour since 1947. The following 5 days were much warmer, with several areas recording mean temperatures around 6C above average. Between the 12th and 19th temperatures were close to normal, but fell after this and remained low until the 29th. Sea ice was again reported, this time on the 27th when 4mm of ice formed on the Aotea Lagoon at Porirua, an unprecedented event in the 23 years since its formation.

20.6C maximum at Kaikoura Flats on the 31st, -11.3C minimum at Mt Cook on the 14th.

Sunshine:  Sunshine totals for the month reflect the unusually high frequency of south-easterly winds. Eastern areas from East Cape southwards, Wanganui, Manawatu and Central Otago mainly recorded less sunshine than normal, while western areas from Taranaki north and the north of the North Island had high sunshine totals. Auckland, Hamilton and Rotorua had departures above normal of 42, 49 and 36 hours respectively. Gisborne on the other hand recorded 97 hours, its lowest July total since 1963.

[Some totals: Kaitaia 174, Waitangi 164, Whangarei 157, Leigh 176, Auckland 180, Tauranga 182, Whakatane 187, Rotorua 177, Taupo 137, Auckland Aero 181, Hamilton 160, New Plymouth 158, Masterton 88, Dannevirke 91, Gisborne 97, Napier 106, Wairoa 82, Paraparaumu 102, Ohakea 103, Palmerston North 78, Levin 106, Wellington 92, Stratford 117, Wanganui 101, Westport 132, Arapito 135, Hokitika 125, Greymouth 107, Nelson 147, Blenheim 146, Grassmere 142, Kaikoura 113, Mt Cook 81, Methven 116, Christchurch 105, Timaru 119, Oamaru Aero 120, Omarama 130, Palmerston 108, Dunedin Aero 98, Dunedin 89, Te Anau 64, Queenstown 93, Cromwell 77, Alexandra 67, Gore 77, Invercargill 72, Campbell Is 5.3 {2nd lowest}, Chatham Is 51 {lowest}].

Sources: NZ Met. Misc. pub. 107 (Climatological table, NZ Gazette) and NZ Met. Misc. pub. 109 (Meteorological Observations).

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