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Author Topic: New Zealand Weather Summary for 1997  (Read 397 times)

Offline Sheldybett

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New Zealand Weather Summary for 1997
« on: June 22, 2019, 11:06:44 AM »
Weather in 1997

1997 was another year with extreme climate events in New Zealand, bringing record low rainfall in parts of Buller, Nelson and Marlborough, and very dry conditions in Marlborough, south Canterbury and Manawatu. The year ended with extremely dry conditions and agricultural drought in Marlborough, and parts of Canterbury and Hawke's Bay. New Zealand had a sunny year overall, especially over central New Zealand but it was cool.

A mix of La Niña and El Niño patterns was responsible for several of the extreme climate events with new records of rainfall and temperature. The tail end of the La Niña pattern caused four tropical cyclones to affect the New Zealand area from January to March. There were many flood-producing heavy rainfall events and as the year progressed New Zealand had an Indian summer.

The weak La Niña climate pattern, which waned in the late summer of 1996-97, was replaced by a very strong El Niño climate pattern which strengthened during winter and persisted for the remainder of the year. This pattern originated in the tropical eastern Pacific Ocean, where a pool of very much warmer-than-normal ocean water developed.

The El Niño influence on New Zealand's climate became most noticeable from winter onwards, with many more anticyclones over Victoria and Bass Strait. It produced more westerlies over southern New Zealand and to the south, and more southerlies over the rest of the South Island and central New Zealand. This produced the dry patterns in the north of the South Island and higher rainfall in the south of the South Island. It was also responsible for the cooler conditions overall, and the rather sunny year.

Rainfall. 1997 was the driest year since records began in 1932 in the Awatere Valley (Marlborough), and since the 1940s at Nelson and Westport Airports. Other extremely dry locations occurred in Marlborough and south Canterbury. These areas recorded only 60 to 75 percent of normal rainfall.

It was particularly wet in Coromandel and Hawke's Bay. with rainfall ranging from 120 to 140 percent of normal. It was also wet in remaining eastern North Island regions, as well as Southland, Fiordland and much of Otago. Most other regions recorded between 75 and 100 percent of normal rainfall.

Of the four main centres, Wellington was the wettest with 1,156 mm and Christchurch the driest with 571 mm. Auckland amassed 1,149 mm and Dunedin 840 mm. Clyde was the driest town NIWA measured in New Zealand, with only 392 mm. Milford Sound was the wettest populated location measuring 6,655 mm.

Temperatures. It was cool overall, particularly in the south and east of the North Island and eastern regions of the South Island, from Canterbury to Southland, where mean temperatures were mostly between 0.5 and 1.0°C below average. Throughout the remainder of the country mean temperatures were average to 0.4°C below average. The warmest centre was Whangarei, with a mean temperature for 1997 of 15.6°C.

The national average temperature, calculated by NIWA, was 12.3°C, which was 0.3°C below normal. This compares with a 1996 national average temperature of 12.5°C.

The highest extreme temperature for the year was 34.1°C recorded at Timaru Airport in hot north westerlies on 15 December 1997. The lowest temperature for the year was minus 8.8°C, measured at Lauder in Central Otago on the morning of 16 July 1997.

WEATHER

It was a very cold September with the lowest mean monthly temperatures on record occurring at Waimate with 6.1°C. 3.3°C below normal, and the Chatham Islands. 7.7°C, 1.6°C below normal.

Sunshine. 1997 had much more sunshine than normal in the north of the South Island, especially Buller where hours were almost 120 percent of normal, as well as Nelson and Westland, where totals were about 110 percent of normal. It was also sunnier than average in western Bay of Plenty. Hawke's Bay, Wairarapa, Wellington, Marlborough, Canterbury. Westland and Southland, where totals were at least 105 percent of normal. Most other regions experienced slightly-above-average sunshine.

Nelson was the sunniest centre in 1997, recording 2,680 hours. This has only been exceeded twice in NIWA's official historical records; 2,685 hours recorded at Blenheim in 1972 and the extreme 2,711 hours recorded at Nelson in 1931. Nelson began recording sunshine hours in 1930.

Blenheim was the second sunniest centre in 1997 with 2.613 hours, followed by Tauranga and Whakatane, both with 2,415 hours. Blenheim set a new New Zealand record for November with its sunniest (327 hours) since records began in 1930. Of the four main centres, Wellington was the sunniest with 2.168 hours and then Christchurch with 2,156 hours.

Indian summer. New Zealand had a rare Indian summer with warm days, light winds, hardly any rain, and plenty of sunshine, from the last week of April through the third week of May. It was extremely dry in the southwest of the North Island. Coupled with the settled weather and warm temperatures, there was little wind anywhere in New Zealand. Well above normal temperatures occurred, with record high May mean temperatures in the south west.

Floods and storms. There were at least 10 flood-producing rainfall events during 1997, some of which were severe. On 5 April in Fiordland heavy rainfall occurred in a 14-hour storm, with 331 mm recorded at Dumpling Hut (on the Milford Track) and on the same day. 100 mm in parts of Southland. Torrential rainfall occurred in a 6-hour storm on 24 May with 142 mm recorded at Beachlands, Auckland. The same weather system also brought high rainfall to Henderson (84 mm), Auckland Airport (81 mm), and Mt Albert (72 mm).

Heavy rainfall resulted in slips, severe flooding, and a state of emergency in the Wairoa region on 3 June. Unofficial reports of rainfall totalling 400 mm occurring within 24 hours (and 100 mm in 2 hours), were received from the area. Many stations in Northland, Auckland, Coromandel, eastern Bay of Plenty, Gisborne and Hawke's Bay measured rainfall totals ranging from 100 to 250 mm in the 48 hours to 9 am 3 June, and many Northland farms were affected by flooding. On 18 June heavy rainfall occurred in parts of Northland, Coromandel, Bay of Plenty, Wellington. Nelson. Marlborough. Golden Bay and Buller, with totals up to 100 mm to 9 am. Northland again experienced heavy rainfall on 30 June. The rain moved south to affect the Bay of Islands, and Coromandel Peninsula. with many sites recording at least 100 mm during the event. Purerua, in the Bay of Islands, measured 134 mm during the storm, of which 50 mm occurred within an hour.

From 1-3 July heavy rainfall in Coromandel, Gisborne, Hawke's Bay, and eastern Bay of Plenty (with 50 to 80 mm in many places) resulted in slips blocking the Napier to Gisborne railway line, and minor flooding on roads north of Wairoa and low lying rural areas. Heavy rainfall on 9 September in the far north, resulted in floods and slips, especially between Doubtless Bay and Whangaroa/Kaeo. Torrential rainfall and flooding, associated with a convergence zone over Coromandel, occurred in Whitianga on 24 September. Rainfall at Whitianga totalled 60 mm in the hour to 2 pm 24 September, 93 mm in the 2 hours to 2 pm 24 September, 193 mm in the 24 hours to 9 am 25 September, and 291 mm in the 48 hours to 9 am 25 September.

High rainfall in the Wellington region on 4 October resulted in the evacuation of about 50 people in Lower Hutt, and flooding of more than 60 homes along Hutt riverside areas. Isolated land slips closed some Wellington roads and SHI. Rainfalls of over 300 mm were recorded in the Tararuas, more than 200 mm in the Hutt catchment and about 90 mm was recorded in Lower Hutt in the 24 hours to noon on 5 October.

The year ended with heavy rain on the West Coast on 15-16 December with totals up to 370 mm recorded in 48 hours in the Greymouth/Hokitika catchment area. Flooding occurred in Greymouth.

Cyclones. Four cyclones of tropical origin occurred in the first three months of 1997. ‘Drena’ tracked to the west of New Zealand, later crossing the north of the South Island on 10 January. It produced gale northeasterlies in Northland and Auckland, with gusts to 124 km/h recorded at Mokohinau Island. The winds damaged power lines and ripped some roofs off houses. High tides and storm surges caused flooding of homes in Thames. High rainfall also occurred from Kaikoura to coastal Otago.

The remains of tropical cyclone ‘Harold’ affected northern New Zealand at the end of February.

A depression of subtropical origin, ‘Nameless’, affected Northland, Auckland and Coromandel, with warm humid northeasterly conditions. Heavy rain combined with high tides resulted in flooding in Whangarei. Rainfall totalling 106 mm occurred in 24 hours, with 46 mm in a one-hour period. Another ex-tropical cyclone, ‘Gavin’, produced high seas in Northland, the Coromandel and Hicks Bay areas over the night of 11/12 March, with about 150 mm of rainfall in the Gisborne ranges. There was extensive flooding in the Motu area and 109 mm of rain caused surface flooding at Gisborne Airport. The cyclone produced high winds, gusting to 130km/h near East Cape (two houses in Hicks Bay lost roofs), and 100 km/h in very exposed parts of Auckland.

Snowfalls. North Canterbury experienced its first significant snowfall of the winter on 18 June with snow to sea level, and falls to l m deep in some inland areas (i.e. Arthurs Pass). Freezing fog blocked out much of the sun in much of Central Otago from 1-10 July, with extensive hoarfrost, making the region very picturesque. A cold snap on 2 August led to snowfall in high country areas, with road closures. Snow also fell to sea level in Southland. Cold southerlies continued through 5 August, with swells up to 6m and high winds through Cook Strait. On 14 August snow fell to low levels in Southland, with thunderstorms and heavy hail in Invercargill. Snow fell to sea level in Canterbury and Otago, settling in Christchurch on 21 August. The same storm moved northward, bringing significant snowfall to high country areas. Cold south-westerlies brought snowfall to northern Southland, south Otago, inland Canterbury and the North Island's Desert Road on 11 November.

Hailstorms. Severe hailstorms struck Hawke's Bay on 22 March, destroying several million dollars worth of fruit in up to 200 orchards. The hail resembled jagged 20 cent pieces or arrowheads. A notable electrical and hail storm occurred over Wellington during the early morning of 14 July resulting in a domestic terminal at the airport being flooded by melting hail.

New Zealand Official Yearbook 1998.


Sheldybett


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