Author Topic: New Zealand Weather Summary for 1999  (Read 605 times)

Offline Sheldybett

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New Zealand Weather Summary for 1999
« on: June 22, 2019, 11:28:18 AM »
Weather in 1999

1999 was notable for extreme variations and for being the second warmest year since records began in the mid-1850s. Climatic extremes included severe drought in Otago, Canterbury and Southland last summer, and heavy flooding in Northland in January and in the Southern Lakes/Central Otago region in November.

It was the most anticyclonic year on record. More anticyclones than normal occurred over the South Island and to the east of New Zealand resulting in few characteristic ‘roaring forties’ westerly gales and more frequent easterlies over the North Island.

The year started with a strong La Niña climate pattern, which continued through autumn, and then became weak through winter and early spring, only to strengthen again towards the end of the year. However, as the year progressed warm seas around New Zealand and more anticyclonic conditions were the most important features determining New Zealand's winter and early spring climate.

Rainfall. 1999 was one of the driest years since records began in 1932 in parts of Buller and south Canterbury, with rainfall totals about 80 percent or less of normal. It was also very dry in parts of western Bay of Plenty. Other drier than average areas were Auckland, Coromandel, Gisborne, Westland, and coastal Otago. These areas all recorded less than 90 percent of normal rainfall. Arapito, on the north-western corner of the South Island, registered its lowest rainfall since records began (in 1979), with only 73 percent of its average rainfall recorded in 1999.

In contrast it was wetter than average in northern areas of Northland, scattered parts of Hawke's Bay, north Canterbury, Southern Lakes, and the far south-west of the South Island. Rainfall in these regions ranged from 105 to 115 percent of normal.

Of the four main centres, Dunedin was the driest with 591mm, and Wellington was the wettest with 1,273mm. Auckland received 1,191mm, and Christchurch 675mm. Alexandra in Central Otago was the driest location the National Institute of Water and Atmospheric Research Ltd (NIWA) measured in New Zealand, with only 408mm. North Egmont was the wettest location in 1999 measuring 6,909mm.

Temperatures. The national average temperature, calculated by NIWA, was 13.3° C, which was 0.8° C above normal. 1999 was the second warmest year since recordings began in 1853. Other unusually warm years were 1998 with 13.4° C, 1971 with 13.3° C, and 1989 and 1990 both with 13.2° C.

Mean temperatures were between 0.5 and 0.9° C above average throughout much of the South Island, as well as many northern, western, and southern areas of the North Island. There was record warmth in the west and south of the South Island, with mean temperatures at least 1.0° C above average. The warmest centre nationally was Kaitaia, with a mean temperature for 1999 of 16.3° C.

WEATHER

Temperatures were nearer normal, however, in the central North Island, and many eastern regions from Gisborne to north Canterbury.

February through March, and May through July periods, were much warmer than average. Warmer than normal sea surface temperatures persisted throughout the year in the mid and north Tasman Sea, contributing to the very warm conditions.

The highest extreme temperature for the year was 37.0° C recorded at Alexandra in hot north westerly conditions on 8 February. The lowest recorded temperature for the year was minus 9.8° C, measured at Tekapo on the morning of 6 July.

Sunshine. 1999 had more than normal sunshine in many southern arid western areas, with hours between 105 and 115 percent of normal. In contrast, below average sunshine hours occurred from the Waikato north. Invercargill had its sunniest year, since records began in 1932, with 278 hours more than average.

Nelson was the sunniest centre in 1999, recording 2,540 hours, followed by Blenheim with 2,477 hours, and Tauranga with 2,427 hours. Of the four main centres, Wellington was the sunniest with 2,161 hours, and then Christchurch with 2,037 hours.

Floods and storms. There were at least 16 flood-producing events during 1999, some of which were severe.

Rainfall totalled almost 100mm at Napier Airport (with higher totals at some inland sites) in the 18-hour period to 9am on 18 January, resulting in surface flooding in some areas. Rainfall was also heavy in Dargaville with thunderstorms and surface flooding.

High intensity rainfall in parts of Northland resulted in severe flash flooding in a number of Hokianga settlements, such as Panguru and Omapere on 21 January. Rainfall totalling 211mm was reported in five hours at Opononi. Flood waters were extensive, with massive land slips, and many roads and bridges washed out. The same weather system also produced extremely high intensity rainfall and serious flooding in Pukekohe, where rainfall totalled 135mm in four hours, and as much as 50mm in an hour that night. About 80 elderly residents were evacuated.

Thunderstorms with lightning affected parts of Wellington and Wairarapa during the evening of 12 March, with surface flooding overnight at some Hutt Valley and Kapiti Coast locations.

A mix of high intensity rainfall in the Dargaville catchment, combined with low pressure and a very high tide on 17 April resulted in severe flooding in the township and local farmland.

Extremely high rainfall lashed parts of the Northland region again on 25–26 April, with flash flooding, landslips, and widespread flooding in some low-lying areas. The Kaeo area of the Bay of Islands was severely affected, with rainfall totals of more than 200mm in 48 hours.

A low to the west of northern New Zealand produced further high intensity rainfall in northern New Zealand on 30 April. Some locations in Whangarei had rainfall totals of 120mm in three hours.

Extremely heavy rainfall deluged Rotorua on 1 May. Rainfall totalling 214mm fell in the 12-hour period to 1pm (with 47mm in one hour). This flooded low-lying areas of the city as well as causing slips and washing out roads around the lake. There was also severe lightning and surface flooding that evening in parts of Auckland. The thunderstorms produced localised downpours, with firefighters called out to pump water from 60 flooded basements.

Further heavy rainfall occurred in the Wanganui high country on 16 May, with the Whanganui River in flood, running 6m above normal, as well as surface flooding slips in some areas, including the Awakino Gorge and Uruti. Rainfall totalling 470mm was recorded in the 72 hours to 5pm at the North Egmont Visitor Centre.

Heavy rainfall accompanied by thunderstorms occurred in Hawke's Bay during the night of 4–5 June, with 100mm reported in parts of the Heretaunga Plains over a few hours. Napier City recorded 70mm in the 24 hours to 9am on 5 June, with surface flooding in many suburban streets. Water lapped at doorsteps in parts of Havelock North. Ohiti, at Roy's Hill recorded 120mm between midnight and 9am.

Significant rainfall occurred throughout Banks Peninsula, and north Canterbury on 17 July, with rainfall totalling 122mm at Le Bons Bay in the 24 hours to 9am on 18 July, and 51mm in Christchurch City during the same period. The Avon River overflowed in some areas. The heavy rain and an unusually high tide resulted in some streets in Kaiapoi being under a metre of water, but no houses were evacuated.

Significant rainfall occurred in Buller on 5 October with some slips and flood damage in the region. Rainfall in the 24-hour period was as high as 142mm at Westport Airport.

Heavy rainfall totalling more than 200mm occurred at The Hermitage, Mt Cook Village, between 9pm 31 October and 3pm 1 November.

Further high rainfall occurred in Northland on 3 November and then in Auckland, Coromandel, and Bay of Plenty on the 4–5 November, with a 2-day rainfall total of 182mm measured at Waihi, and 100mm in other areas.

Additional rainfall occurred on 10–11 November totalling 50 to 60mm in many parts of Northland, Coromandel, and Bay of Plenty, with surface flooding in many areas. The worst affected areas were the Hokianga township of Panguru, and eastern Bay of Plenty's Waimana (where rainfall was much higher, and at least nine farms were flooded). High rainfall also drenched Golden Bay, with a total of 170mm measured at Upper Takaka on 10 November.

Moist northwesterlies and continuous electrical storms produced torrential rainfall in Fiordland, south Westland, and the Southern Alps from 14–16 November with rainfall totalling 400mm at the Homer Tunnel, and at least 100mm in Queenstown in the 48 hours to 9am on 16 November. The Queenstown total of 205mm over a three-day period was the highest in records going back to 1871. Southern Lake levels ran extremely high, with Lakes Wakatipu and Wanaka both flooding their foreshores. Lake Wakatipu reached its highest level on record since Pākehā settlement, and Lake Wanaka since September 1878. The flood waters from these lakes and surrounding rivers caused the Clutha River to be in high flood (flowing at six times its normal volume). The Mataura River, in Southland, was also in flood.

A mix of high rainfall and high tidal conditions resulted in further surface flooding, this time from south Taranaki to Manawatu, (including Wanganui) from 27–29 November, with rainfall between 75 and 100mm in many areas, and more than 150mm around Normanby. The flooding was worst in the Kopane area, where the Oroua River breached its banks.

Cyclones. Unlike some La Niña years, 1999 was relatively ‘quiet', with only one cyclone of tropical origin just brushing the country. The remains of tropical cyclone ‘Frank’ brought rainfall to many areas on 26–27 February. Rainfall totals ranged from 20 to 80mm in Canterbury, providing temporary relief from very dry conditions.

Snowfalls. Bitterly cold southerlies brought snowfalls to high country regions (including Te Anau and Porters Pass) on 16–17 April and resulted in a temporary closure of the North Island's Desert Road.

Cold southerlies brought low temperatures to eastern regions on 5 May and snowfall to the North Island's Desert Road (resulting in its closure between Waiouru and Rangipo). Snow also covered the ranges about Hawke's Bay, and fell in the Rimutakas.

The western Otago/Southern Lakes region experienced the heaviest snowfalls on record on 2–3 July. More than a metre of snow was measured at Coronet Peak, with depths to 40cm reported in some low-lying rural areas. A large number of residents were without power.

Cold southerlies brought snow to low levels in the south and east of the South Island from 26 July. Snow depths of 2.5cm occurred in Christchurch. Depths up to 25cm were reported in parts of Southland and Otago. Showers of sleet and hail (with some isolated heavy falls) occurred in the south of the North Island, with heavy snowfalls in the Wairarapa high country. The Ruapehu area received its first significant snowfall of the winter, with the Desert Road closed by snow and ice from 26–29 July. Snow also settled on the Rimutaka Hill road north of Wellington.

Bitterly cold southerlies occurred on 17–18 August with snowfall in high country areas of the South Island, and significant falls in most North Island ski areas.

Snow fell to low levels on Banks Peninsula (up to 7cm depth in hilly areas), leaving some vehicles stranded for a period.

Hailstorms. A thunderstorm with marble-size hailstones occurred just before the Ruapuna tornado. Thunderstorms with hail reached Hawke's Bay on 13 May and damaged apple orchards.

Severe hailstorms hit parts of Auckland and Waikato. Snow-like drifts of hail lay for some time in Panmure and Mt Wellington and several buildings in Auckland were flooded. Hail was especially heavy about Te Awamutu and SH5 on the Mamaku Plateau where it lay up to 7cm in depth.

Hail occurred during thunderstorms in Coromandel from 4.20pm on 28 November, with hail still lying on the ground at 9pm.

Tornadoes, gales and high winds. A tornado was seen near Te Aroha, in the Waikato, on 17 January during the afternoon.

A tornado, with a diameter of about 100m, was reported at about 2.30pm on 11 March in the Ruapuna district (west of Ashburton). This lifted an apple tree, dropping it some distance away.

Gale-strength northwesterlies buffeted eastern regions of the South Island on 16 May, being particularly severe in parts of Banks Peninsula, causing a number of trees to fall, and power outages.

Hurricane-force northwesterlies affected the south-west of the country on the 26 May, with gusts to 172km/h recorded at both Puysegur Point and South West Cape.

On 6 May gale-force southerlies and high seas affected Wellington and Cook Strait (where 165km/h winds were reported), with swells averaging 6m, and peaking at 11m, resulting in the cancellation of Cook Strait ferry crossings. In Wellington a container ship broke its moorings.

Severe, damaging northwesterlies occurred on the morning of 2 July. Violent wind gusts to 150km/h were reported in the Tuatapere and Middlemarch areas, with significant property damage. Gusts to 133km/h were recorded at Lauder (near Alexandra).

New Zealand Official Yearbook 2000.


Sheldybett

Offline Rwood

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Re: New Zealand Weather Summary for 1999
« Reply #1 on: June 22, 2019, 04:14:06 PM »
Remember that these summaries should not extend beyond 2000 as NIWA has full annual summaries for 2001 onwards on their website.

Offline Sheldybett

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Re: New Zealand Weather Summary for 1999
« Reply #2 on: June 22, 2019, 04:33:43 PM »
Okay, I understand it, because you may be wrong as NIWA has a 2000 annual weather summary not 2001 onwards. Anyway first half of a year is similar to this year, but December 1999 is rather cool with wet conditions in the Lower North Island.

Offline Rwood

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Re: New Zealand Weather Summary for 1999
« Reply #3 on: June 22, 2019, 04:41:35 PM »

Yes you're right, their online summaries do start at 2000.


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