Climate Summary: A mild winter for much of the country

Full summary: Climate_Summary_Winter_2014_2.docx

A mild winter for much of the country.

Overview

Overall, winter 2014 was characterised by mean sea level pressures that were higher than normal over and to the west of New Zealand. This resulted in an anomalous westerly flow across most of the country with the exception of the north of the North Island where anomalous easterly flow occurred. These westerly and easterly flow anomalies respectively contributed to the difference in rainfall anomalies observed across New Zealand during the season, with eastern parts of the South Island observing a drier than normal winter and Northland observing a winter that was much wetter than normal. Notably, it was an exceptionally warm start to winter. In June 2014, a north-easterly flow anomaly dominated across the country, and this was a contributing factor to what was New Zealand’s warmest June on record.

As noted above, winter temperatures across the country were mild overall. The season started out extraordinarily warm, however temperatures returned to near-normal in July and August. Winter was especially mild for the South Island where temperatures were predominantly above average (0.5 to 1.2°C above average). Additionally, some parts of Central Otago observed winter temperatures that were well above average (more than 1.2°C above average). An exception was isolated parts of mid-Canterbury and coastal Marlborough, where near average winter temperatures were observed (within 0.5°C of average). In the North Island, winter temperatures were above average in parts of Northland, Auckland, Waikato, Bay of Plenty, Gisborne, Hawke’s Bay, Manawatu and Wellington, with near average temperatures across the remainder of the island. The nation-wide average temperature in winter 2014 was 9.1°C (0.8°C above the 1971-2000 winter average from NIWA’s seven station temperature series which begins in 1909) [interim value].

There was a notable difference in winter rainfall anomalies experienced within both the North and South Islands. In the North Island, winter rainfall was well above normal (more than 149% of normal) throughout Northland, yet rainfall was below normal (50-79% of normal) in southern Waikato, Hawke’s Bay, Manawatu and the Kapiti Coast. In the South Island, winter rainfall was above normal (120-149% of normal) in Arthur’s Pass, Mount Cook National Park, Wanaka and south-western parts of Southland. In contrast, rainfall was below normal for large parts of the eastern South Island. Areas around Blenheim, Kaikoura, Christchurch, Timaru and Dunedin only received approximately half to two-thirds of normal winter rainfall. Winter rainfall was near normal for remaining areas of the South Island.

At the start of winter, soils were drier than normal for parts of Northland, Auckland, northern Gisborne, the Central Plateau and Hawke’s Bay, whereas they were wetter than normal throughout the eastern South Island, the Southern Lakes and Central Otago. As of 1 September 2014 soil moisture had returned to near normal levels for large parts of the country. The exception was parts of Taranaki, the West Coast and Tasman as well as the districts of Selwyn, Waimakariri and Timaru, where soils were slightly drier than normal for the time of year.

Winter sunshine was abundant for much of Waikato, North Canterbury, the Mackenzie Country, the Southern Lakes and Central Otago where winter sunshine was above normal (110-125% of normal), and in some cases well above normal (more than 125% of normal). In contrast, parts of southern Wairarapa received below normal winter sunshine (75-89% of normal). Remaining areas of New Zealand observed near normal winter sunshine totals (within 10% of normal).

Full summary: Climate_Summary_Winter_2014_2.docx

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