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Author Topic: New Zealand Weather Summary for 1996  (Read 750 times)

Offline Sheldybett

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New Zealand Weather Summary for 1996
« on: June 03, 2019, 05:21:24 PM »
1996 was a year of contrasting climate conditions in New Zealand with new records of extreme rainfall and temperature. There were at least ten flood-producing events. Severe snowstorms with extremely low temperatures hit Southland in July. Some damaging wind events occurred, and at the end of the year several severe hail storms (all within a four-week period) produced damage in horticultural areas. Cyclone Fergus ended the year with record rainfall in the Coromandel.

A weak La Nina pattern persisted throughout the year. It originated in the tropical eastern Pacific Ocean, where a pool of colder than normal ocean water developed, and is one of the reasons why northern New Zealand, for the second consecutive year, had a mild, wet winter, while the south was cold. During La Nina episodes cyclones of tropical origin are also more likely to pass near New Zealand.

More depressions tracked across New Zealand during 1996, producing stormy westerlies over the North Island. At the same time, more frequent cooler easterlies on the tail of these storms prevailed over the southern half of the South Island.

Rainfall. 1996 was rather wet over much of the North Island, with 125 to 150 percent of average rainfall in the Hauraki Gulf, South Auckland, Waikato and the King Country. Waiheke Island had its wettest year since records began in 1914. It was also wetter than usual in many other North Island regions, with rainfall between 110 and 125 percent of normal. Only Whangarei and the Wairarapa had near average rainfall.

WEATHER

There were contrasting conditions in the South Island. Only 75 percent of normal rainfall occurred around Hanmer. Central Otago and Southland received rainfall between 85 and 90 percent of normal.

Of the four main centres, Auckland was the wettest with 1,417 mm and Christchurch the driest with 608 mm. Wellington amassed 1,266 mm and Dunedin 786 mm. Clyde was the driest town measured in New Zealand, with only 376 mm. Milford Sound was the wettest location, with 6,295 mm.

Temperatures. Colder conditions, with temperatures more than 1°C below average, occurred in inland Otago and Canterbury. Temperatures were 0.5°C or more below average in the remainder of South Canterbury, Otago, Southland, and inland Nelson/Marlborough. Temperatures were also below average in much of Taranaki and Wanganui.

In contrast, temperatures were close to average in Westland, and throughout much of the North Island, and above average in the Kaipara/South Auckland areas. The national average temperature was 12.5°C, which was 0.1°C below normal. This compares with a 1995 national average temperature of 12.6°C.

September was the second warmest in New Zealand since records began in 1853, with record high temperatures in Levin and Wellington (Kelburn), and second highest since records began in Ruakura, East Taratahi, Palmerston North and Gore. Highest temperature for the month, 28.0°C, was recorded at Waimate. The national average temperature for September was 11.7°C, 1.4°C above the long-term mean.

Extremely low mean November temperatures were recorded in inland regions of both islands, with temperatures 2 to 3C below normal in some areas. Record, or near record, low mean temperatures were recorded at Taumarunui, Waimate and Milford Sound.

The highest extreme temperature for New Zealand in 1996 was 34.7°C, measured at Christchurch Airport on 7 February. The lowest temperature for the year was −15.3°C, recorded at Tapanui, Southland on 4 July, the same day as lowest ever minimum air temperatures were recorded at both Gore (−10.5°C) and Invercargill (−9.0°C).

Sunshine. There were record high sunshine hours in Buller, with over 115 percent of normal. It was also very sunny in the Bay of Plenty, Westland, Otago and Southland, all having 105 to 110 percent of normal hours. Slightly above average sunshine totals occurred over much of the South Island (apart from Canterbury, which had below average hours). Sunshine was close to average in many North Island areas. Record high sunshine hours occurred at Arapito (Karamea) with 1,916 hours (306 hours above average), the highest since records began in 1979. It was very cloudy in Gisborne which recorded a record low of 1,898 hours, only 86 percent of the annual average, and the lowest in 60 years of records.

Blenheim was the sunniest centre, recording 2,583 hours, followed by Nelson with 2,483 hours and Tauranga with 2,463 hours.

Floods. There were at least ten flood-producing rainfall events during 1996, some of which were severe. On 19 January a one-and-a-half-hour ‘cloud burst’ resulted in 50 mm of rainfall in Greenlane (Auckland) and flash flooding in east Auckland. Events of this magnitude occur on average once every 20 years. From 24 to 28 January a storm of tropical origin over the Kermadecs brought rainfall totalling 362 mm in 48 hours at Raoul Island, the highest 2-day rainfall total since records began in 1937. The edge of the same storm produced surface flooding in Gisborne.

Heavy rainfall on 7-8 February brought surface flooding and roads blocked in areas of coastal South Canterbury, with significant damage to crops south of Ashburton. High rainfall (more than 300 mm inland, and about 160 mm along the coast) occurred in the Gisborne region over the last two days of March, resulting in slips and surface flooding. Northern Hawke's Bay was also affected.

Thunderstorms and heavy rainfall affected northern and eastern areas of the North Island over the night of 21-22 May. There was extensive flooding at Pukekohe, and Waikato, Bay of Plenty, Hawke's Bay and Wellington were also affected by heavy overnight rain. Thunderstorms and heavy rainfall produced flooding in Waikato on 12 September, leaving paddocks and part of State Highway 1 flooded. Heavy rainfall occurred in Fiordland on 7 October. The Homer Tunnel was damaged after heavy rainfall (178 mm in 20 hours) resulted in avalanches. Flooding was reported at a number of sites on SH6 from Makarora to Wanaka, and Cromwell to Luggate. On 29-30 December Cyclone Fergus brought over 300 mm of rain to Northland, and 242 mm at Whitianga, closing roads and disrupting holiday arrangements.

Tornadoes. Small tornadoes caused damage in Ruakaka, Northland, on 29 April; in the Tauranga area (with a waterspout) during the evening of 22 May, with several trees uprooted in Bethlehem and rooves lifted further west; and a small tornado, associated with a thunderstorm, produced a path of damage through Whitianga and Cooks Beach (Coromandel Peninsula) on 15 August, taking rooves off several houses, uprooting trees and damaging power lines.

Gales and storm. Northwesterly gales caused widespread power cuts and property damage north of Gisborne early on 1 July, leaving thousands of families without electricity. Tolaga Bay was hardest hit, with many buildings damaged and trees blown over.

Severe wind occurred in parts of New Zealand on 7 October. Tornado-like winds that morning caused a trail of damage to property in Hokitika. Gales and heavy rainfall affected the country on 13 October, with power outage and damage to property in Auckland, Wellington and the Wairarapa. Gusts to 89 knots (165 km/h) were recorded at Castlepoint, and 59 knots (110 km/h) noted in Auckland.

A northwesterly storm brought rain and high winds to much of New Zealand over 18-19 November, as an exceptionally deep depression passed over the South Island, with trees fallen in places, and power cuts in Poverty Bay and coastal Otago. Wind gusts to 156 km/h occurred at Castlepoint, and 132 km/h in Wellington. The system also produced extremely low atmospheric pressures (971.8 hPa) at Christchurch and Timaru airports during the afternoon of 19 November.

Snowfalls. The year's first wintry southerly outbreak on 26 May brought significant snowfall to North and South Island ski fields, and on the Desert Road (which was closed).

From 9 to 11 June, light snow fell to low levels in Southland, in parts of inland Otago, and Dunedin hill, with blizzard conditions reported further south about Mosgiel. There was snow to 23cm near Queenstown, and the heaviest June snowfall in 10 years at Coronet Peak. The Rimutaka Hill Road and the Desert Road were closed, and the Napier-Taupo road, temporarily. The snow falls were greatest in Canterbury, with 42 cm in some inland areas. In Christchurch light snow settled.

A severe chill brought heavy snowfall to Southland and Otago, with a bitterly cold southerly outbreak over 1 and 2 July, followed by clearing weather with severe frost. The northern motorway out of Dunedin and some Southland roads were closed. Ice made many roads extremely dangerous and the Rimutaka, Desert, and Napier-Taupo roads were closed by snow on 2 and 3 July. Snow was up to 35 cm deep on the Napier-Taupo Road on 4 July, isolating some areas of Hawke's Bay, and said to be the worst snowstorm in 40 years. A rare snowfall was reported on the Moehau Range, Coromandel. Snow also fell in areas around Christchurch on 2 July. Many water-pipes burst in Invercargill when temperatures were high enough for the thaw to begin on 10 July. Lowest ever minimum air temperatures were recorded at Manapouri, Gore, Invercargill, Dunedin Airport and Hororata.

Snow fell to sea level overnight on 21 August in both Dunedin and Christchurch, settling in places, and in the North Island closed the Desert Road. Further snow fell to sea level in coastal Otago on 29 August, being heavy in some rural areas. This event also closed the North Island's Desert Road.

Hailstorms. A dramatic hailstorm, with lightning, hit parts of Canterbury in the afternoon on 5 December. Hailstones of marble to walnut size (up to the size of a 20c piece) were reported in Belfast, near Christchurch. This was followed the next day by severe hail, up to 15 mm in diameter, in Hawke's Bay. Large hail also affected Bay of Plenty.

Further damaging hailstones occurred in Appleby, Nelson, during the afternoon of 16 December. Damage to apple crops resulted in millions of dollars lost to orchardists.

New Zealand Official Yearbook 1997


Sheldybett

Offline Rwood

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Re: New Zealand Weather Summary for 1996
« Reply #1 on: June 03, 2019, 06:45:29 PM »
Wrong about Kelburn rainfall (by omission) - it was very close to average.

NIWA were using rather melodramatic language in reports at that time - such a year would now be considered fairly typical as far as extreme events go. The language now is a bit more restrained (after all if every year is a "year of extremes" then it's not really an "extreme" year).
« Last Edit: June 03, 2019, 06:58:57 PM by Rwood »

Offline Sheldybett

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Re: New Zealand Weather Summary for 1996
« Reply #2 on: June 04, 2019, 02:44:54 PM »
I did not know about that, because I thought the rainfall has up to date info today as in 1996. Which is a actual total rainfall by today's standards.

Offline Rwood

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Re: New Zealand Weather Summary for 1996
« Reply #3 on: June 04, 2019, 05:11:10 PM »


It's not about wrong averages or anything - the average being used then was perfectly OK - the report was oversimplified re rainfall and someone failed to include Wellington and nearby parts as having normal rainfall.


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