Climate summary for - October 2016

03 November 2016

A wet month for parts of the South Island and eastern North Island, warm in most locations.

Rainfall	October rainfall was generally above normal (120-149%) or well above normal (> 149%) for much of the southern South Island, including Otago, Southland, southern Canterbury and southern Westland, in addition to Nelson, eastern Tasman, western Marlborough, coastal Gisborne and northern Hawke’s Bay, and eastern Bay of Plenty. Rainfall was generally near normal (80-119%) or below normal (50-79%) for much of the remainder of the North Island and the central South Island north of Otago. However, rainfall was well below normal (< 50%) in coastal Wairarapa and isolated parts of the far North.
Temperature	October temperatures were above average (+0.50°C to +1.20°C) throughout much of New Zealand. Temperatures were generally near average (-0.50 to +0.50°C) from western Northland to western Waikato, central Bay of Plenty, and from Tasman to central Otago.
Sunshine	October sunshine was below normal (75-89%) or well below normal (< 75%) in parts of the south-western North Island, central Canterbury and central Otago, whereas above normal (110-125%) sunshine was observed in western Northland, western Waikato, and parts of Westland. In addition, well above normal (> 125%) sunshine was experienced in far northern Northland.
Soil Moisture	At the end of October 2016, soil moisture levels were much lower than normal for the time of year in coastal northern Canterbury and coastal Wairarapa. Soil moisture levels were above normal for the time of year in much of Gisborne and northern Hawke’s Bay, Nelson, eastern Tasman, western Marlborough, and Fiordland east to coastal Otago. Soil moisture levels were near normal for the remainder of the country.

Overview

During October 2016, mean sea-level pressures were much lower than normal over and to the southwest of New Zealand, which resulted in a prevalence of winds from a westerly direction. However, several storms during the month took shape south and east of the country, which resulted in periods of southerly and easterly wind flows as well.

Wetter in the south

Despite the prevalence of westerly winds in October, several storms passing to the south and east of New Zealand led to wetter than normal conditions in the southern and northern South Island as well as the north-eastern North Island. Some parts of Otago received more than double their normal October rainfall, while much of the rest of the southern South Island recorded well above normal (> 149%) or above normal (120-149%) rainfall. The northern South Island also had a small area with very wet conditions, as Nelson received 204% of its normal October rainfall amount. Several storms moving east of the North Island delivered plentiful rainfall to Gisborne, Hawke’s Bay and central Bay of Plenty, with Wairoa receiving 205% of its normal October rainfall. However, these storms did not aid coastal Wairarapa which received below normal (50-79%) to well below normal (< 50%) rainfall totals. Northern Northland was also dry in October, with Kerikeri only receiving 45% of its normal rainfall total.

October temperatures were average (-0.50°C to +0.50°C) to above average (+0.51°C to +1.20°C) throughout most of New Zealand. The above average temperatures in the southern South Island were aided by warm nights associated with plentiful cloud cover, which act to insulate the land and prevent heat from escaping into the atmosphere.

The nationwide average temperature in October 2016 was 12.8°C. This is 0.67°C above the 1981-2010 October average from NIWA’s seven station temperature series. (A series which begins in 1909 and is an interim value).

Drier in central eastern areas

At the end of October 2016, soil moisture levels were much lower than normal for the time of year in coastal northern Canterbury and coastal Wairarapa. Soil moisture levels were above normal for the time of year in much of Gisborne and northern Hawke’s Bay, Nelson, eastern Tasman, western Marlborough, and Fiordland east to coastal Otago. Soil moisture levels were near normal for the remainder of the country.

Cloudy skies associated with higher than normal rainfall totals meant that October sunshine was below normal (75-89%) or well below normal (< 75%) in parts of the south-western North Island, central Canterbury and central Otago, whereas above normal (110-125%) sunshine was observed in western Northland, western Waikato, and parts of Westland, which resulted from periods of easterly winds that caused sinking motion and increased sunshine on the western coasts of both islands. In addition, well above normal (> 125%) sunshine was experienced in far northern Northland.

Further highlights:

The highest temperature was 27.1 °C, observed at Christchurch (Riccarton) on 19 October and at Wairoa on 20 October.
The lowest temperature was -3.8 °C, observed at Mt Cook Airport on 22 October.
The highest 1-day rainfall was 160 mm, recorded at Milford Sound on 18 October.
The highest wind gust was 180 km/hr, observed at Cape Turnagain on 5 October.
Of the six main centres in October 2016, Auckland was the warmest, Tauranga was the sunniest and driest, Wellington was the wettest, Dunedin was the coolest, and Hamilton was the cloudiest.
Of the available, regularly reporting sunshine observation sites, the sunniest four locations in 2016 so far (1 January – 31 October) were Richmond (2318 hours), Blenheim (2107 hours), Takaka (2061 hours) and New Plymouth (2020 hours).