National Climate Summary – October 2000

 EXTREMELY DRY IN GISBORNE AND HAWKE’S BAY
 WET IN THE TARARUAS, CANTERBURY AND CENTRAL OTAGO
 SUNNIER AND A LITTLE WARMER THAN NORMAL IN MANY REGIONS

October rainfall was extremely low in Dargaville, Gisborne, and parts of Hawke’s Bay, with totals less than quarter of normal. It was also dry in much of the north and east of the North Island. In contrast the first two weeks were stormy in several other parts of New Zealand.

Heavy rainfall and high winds battered the central North Island from 1-3 October, with widespread surface flooding from Taranaki to Wellington. The Wairarapa was particularly hard hit. A mini-tornado caused damage in Paraparaumu on 9 October, and more flooding occurred in the Wairarapa on the 10th. A fierce southerly storm struck Banks Peninsula, Canterbury, and the Kaikoura Coast on 12 October, with damaging winds and flood producing rainfall. The Tararuas and parts of Canterbury and Central Otago received at least double the normal average rainfall for the month. It was also wetter than normal in other southwestern North Island regions, South Island alpine regions, and Southland.

October temperatures were a little above average over most of the North Island and northern South Island. However, cooler conditions prevailed in inland south Canterbury and Otago. The national average temperature was 12.4°C, +0.3°C above average. It was sunny throughout much of the North Island, and northern South Island. Other regions experienced near average sunshine. October’s climate patterns were due to more frequent anticyclones (“highs’) than usual passing over northern New Zealand, with depressions (“lows”) often south of the country. Stronger westerlies than normal occurred over the South Island and lower North Island.

VERY DRY IN GISBORNE AND HAWKE’S BAY

Rainfall was less than 25 percent (quarter) of average in Gisborne and much of Hawke’s Bay, and less than 50 percent (half) of average in parts of Northland. It was also drier than average in Auckland, Coromandel, Bay of Plenty, and Taupo, where totals were less than 75 percent of normal. Extremely low October rainfall was recorded at:

Location October rainfall
(mm) Percentage
of normal Year
records began Comments
Dargaville 20 23 1943 Lowest
Gisborne Airport 6 10 1905 Lowest
Napier Airport 7 13 1950 Lowest

VERY WET IN THE TARARUAS, AND PARTS OF CANTERBURY AND CENTRAL OTAGO

Rainfall was well above average in the Tararuas, and parts of Canterbury and Central Otago, with totals about 200 percent (double) normal in some areas. It was also wetter than normal other southwestern North Island regions from King Country to the Hutt Valley, as well as Wairarapa, South Island alpine regions, most other Otago areas, and Southland, where rainfall was at least 125 percent of normal.

A LITTLE WARMER THAN NORMAL IN MANY REGIONS

October temperatures were about 0.5°C above average over most of the North Island and northern South Island. However, cooler conditions prevailed in parts of inland south Canterbury and Otago, with mean temperatures about 0.5°C below normal.

SUNNY IN MANY REGIONS

Sunshine and solar radiation totals were 105 to 110 percent of normal throughout much of the North Island, and northern South Island. Other regions experienced near average sunshine.

HIGHLIGHTS

Extreme temperatures
 The lowest measured air temperature was -5.6oC, recorded at The Chateau, Mt. Ruapehu on the 19th. The lowest October air temperature on record at The Chateau, Mt. Ruapehu is –8.3 oC.
 The highest measured air temperature was 28.0 oC, recorded at Waipara on the 29th, which is the highest October temperature on record for that site in North Canterbury (records began in 1990).

Heavy rainfall and floods: 1-3 October
 Heavy rainfall and high winds battered the central North Island, with widespread surface flooding, and many road closures, particularly in the Wairarapa. The Waipoua River burst its banks north of Masterton, drenching surrounding farms and low-lying areas. The Manawatu River was also very high, with extensive surface flooding in the region. Rainfall in the Tararuas totalled more than 750 mm in 72 hours. One house in Eketahuna was evacuated. Surface flooding and slips also occurred in Taranaki, and King Country. Winds blew part of an iron roof off a house in Dannevirke. Gales battered Canterbury on the 2nd, causing damage to trees, power lines, and roofs. Some surface flooding also occurred further south, in the Queenstown area.

Hailstorm: 9 October
 Thunderstorms, with lightning and pea-size hail occurred in Invercargill

Mini-tornado - waterspout: 9 October
 Winds described as those of a mini-tornado – waterspout struck a house at Paraparaumu Beach, ripping iron off the both house and garage roofs and uprooting trees, and fences in the same street between 8.20 and 8.30 am.

Further floods: 10 October
 Further high rainfall (300 mm in the Tararuas) resulted in further flooding in Eketahuna.

Extreme winds and more floods: 12-13 October
 Banks Peninsula, Canterbury, and the Kaikoura Coast felt the effects of a severe southerly storm on 12 October, with damage to roads, bridges, and roofs running to millions of dollars. Floodwaters covered roads in the Redcliffs-Sumner area. Broken power lines resulted in 8000 houses in mid-Canterbury, and 1000 homes on Banks Peninsula being without electricity. Rainfall in the city totalled 70 mm for the 48 hours to 9am on the 13th. Lyttelton was isolated for several hours. A floating marina was destroyed by storm force winds (mean winds speeds at least 89 km/h) and 4 metre swells. 32 boats sank and others were seriously damaged. Hurricane force winds (having average speeds of up to 120 km/h) were measured at Le Bons Bay near Akaroa. The southerlies produced 6 metre swells and 160 km/h winds in Cook Strait, and gusts of 139 km/h at Baring Head. Further north, power lines blew down in Otaki. Slips closed SH43 between Stratford and Taumaranui, and the Desert Road was closed by heavy snow. At New Plymouth, a tanker and a yacht broke their moorings in 4 metre swells. Considerable wind damage occurred to asparagus crops in Hawke’s Bay. In Auckland, a fallen tree caused two boats to break their moorings.

For further information, please contact:
Dr Jim Salinger, NIWA - Auckland,
Tel (09) 375 2053 (Business) or (09) 527 3939 (after hours)
or Stuart Burgess, NIWA - Wellington, Tel (04) 386 0569

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