National Climate Summary – Winter 2011: Dry, Sunny With Snow

National Climate Summary – Winter 2011: Dry and sunny, with a snowy finish.

• Precipitation: Overall, it was a relatively dry winter for many regions. But two extreme polar outbreaks produced snow falls in unusual locations.

• Sunshine: A sunny winter for most regions.

• Temperatures: A very warm winter in the north and east of the North Island, as well as Central Otago and the Lakes District.

Winter arrived late this year – June was exceptionally warm (the 3rd warmest on record), being characterised by frequent northeasterly winds. Temperatures remained elevated through a stormy, unsettled and extremely windy (westerly) July, until a polar blast on 24-26 July delivered a bitterly cold air mass over the country. Extremely cold air affected Canterbury, the Kaikoura coast, Nelson, Wellington, Wairarapa, Manawatu, Hawkes Bay and Taranaki during 25-26 July, and snowfall was heavy and to low levels over Canterbury, the Kaikoura Ranges (both Inland and Seaward), the Richmond Ranges, Tararua and Rimutaka Ranges, the Central Plateau, and around Mt Egmont. Brief dustings of snow were also reported in the ranges of Motueka and Northland on 25 July. August continued with more of the same – a second polar outbreak affected New Zealand on 14-17 August, bringing heavy snow to unusually low levels across eastern and alpine areas of the South Island, as well as Wellington.

Snow also fell across the lower North Island, with flurries in unusual locations further north. The long-lived southerly winds between 14 and 17 August again delivered extremely cold air over the country, with numerous low temperature records broken over this period. However, the last week of August was rather sunny, with some unusually ‘spring-like’ temperatures.

Overall, winter 2011 was characterised by more southwest winds than usual over New Zealand, with highs over the Tasman Sea and lows to the southeast of the country. It was generally a sunny and rather dry winter, and was much warmer than usual in the north and east of the North Island, as well as Central Otago and the Lakes District. Sunshine totals were above normal for many regions, excluding Auckland, the southwest of the North Island, the northwest of the South Island including Hokitika, as well as Southland (where near normal winter sunshine was observed). It was the sunniest winter on record for Taumarunui and Lake Tekapo.

Rainfall was less than half of winter normal for south Canterbury and parts of Otago. For the remainder of the South Island, as well as eastern parts of Northland and north Auckland, rainfall was generally below normal (between 50 and 79 percent of winter normal). It was the driest winter on record for Alexandra and also Leigh (north Auckland). In contrast, coastal Southland experienced above normal winter rains. Elsewhere in the North Island, as well as for the greater Nelson region, winter rainfall was near normal.

Winter mean temperatures were well above average (more than 1.2°C above winter average) across much of the north and east of the North Island, as well as Central Otago and the Lakes District. Below average temperatures (more than 0.5 C below winter average) were observed in inland north Otago, and in parts of the northwest South Island. Elsewhere, winter temperatures were near average. The average temperature for winter 2011 was 8.7°C (0.4°C above the 1971–2000 winter average) using NIWA’s seven-station temperature series which begins in 1909.

Further Highlights:

• The highest winter temperature recorded was 22.4°C at Whitianga on 5 June (a new winter record at this location).

• The lowest temperature recorded was -10.2°C at Manapouri on 26 July (a new all-time record at this location).

• The highest 1-day rainfall experienced was 128 mm recorded at Arthurs Pass on 10 July.

• The highest gust was 189 km/hr observed at Cape Turnagain on 12 July.

• Of the six main centres in winter 2011, Auckland was the warmest, Christchurch the coldest, Hamilton the wettest, Dunedin the driest, and Tauranga the sunniest.

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