Climate Summary for December 2015

An exceptionally dry and sunny December for most of New Zealand

Rainfall

 

Rainfall was below normal (50-79%) for virtually the entire country with well below normal (< 50%) rainfall recorded for the majority of the North Island, as well as parts of Nelson, Marlborough and Otago. Rainfall was near normal (within 20% of December normal) in parts of Southland and southern Canterbury.

Sunshine

A very sunny December with above (110-125%) to well above (>125%) normal sunshine experienced around the country. A number of locations observed record or near-record sunshine hours for December.

Temperature

December temperatures were largely near average (-0.50°C to +0.50°C) across New Zealand. Below average temperatures (-1.20°C to -0.51°C) were recorded along the east coast of the North Island from Gisborne through to south Wairarapa as well as north-eastern parts of the South Island.

Soil Moisture

As of 1 January 2016, soil moisture levels were below normal for the time of year for the entire country with the exception of the Auckland region and Coromandel.  The driest soils when compared to normal exist throughout the Waikato and Taranaki regions as well as parts of the Bay of Plenty.

Overview

During December 2015, strong El Niño conditions continued in the Tropical Pacific.  In New Zealand this contributed to the prevalence of high pressure over and to the west of the country while lower pressure than normal existed to the east of New Zealand. This pressure pattern resulted in more south-westerlies than normal over the South Island and more southerlies than normal over the North Island.

Rainfall

The dominance of high pressure throughout December meant that the month as a whole was very dry with several locations around the country observing record or near-record low December rainfall totals. Less than half of normal rainfall was observed for the majority of the North Island and below normal rainfall (50-79% of the December normal rainfall) was recorded across most of the South Island. No locations recorded above normal rainfall (120-149% of the December normal rainfall) and the only places to observe near normal rainfall (within 20% of the December normal) were parts of Southland and southern Canterbury.

Soil moisture

The lack of rainfall, following a dry November, meant soil moisture levels continued to deplete around the country throughout the month, particularly in the North Island. As of 1 January 2016, soil moisture levels were below normal for the time of year for the entire country with the exception of the Auckland region and Coromandel.  The driest soils when compared to normal existed throughout the Waikato and Taranaki regions as well as parts of the Bay of Plenty.

Sunshine

Sunshine was abundant during December, with above normal (110-125% of the December normal) to well above (>125% of the December normal) normal sunshine experienced all around the country. A number of locations observed record or near-record sunshine hours.

Temperatures 

The sunny skies contributed to December mean maximum temperatures generally staying above (+0.51°C to +1.20 °C above the December average) to well above average (> +1.20 °C above the December average), while the lack of cloud allowed for ideal night-time radiational cooling and thus mean minimum temperatures dipped below (-1.20°C to -0.51°C below the December average) to well below average (<-1.21°C below the December average). This diurnal pattern was largely balanced out with the resulting mean December temperatures being near average (within 0.50°C of the December average) for most parts of the country. 

The exception was along North Island’s east coast from Gisborne through to south Wairarapa where mean temperatures were below average, aided by the prevalence of southerlies over the North Island. The end of December also saw strong north-westerlies bring record breaking daily maximum temperatures. The nation-wide average temperature in December 2015 was 15.6°C (equal to the 1981-2010 December average from NIWA’s seven station temperature series which begins in 1909) [interim value].  

Highlights

Further Highlights include: 

  • The highest temperature was 36.4°C, observed at Leeston on 21 December.
  • The lowest temperature was -0.7°C, observed at Hanmer Forest on 7 December.
  • The highest 1-day rainfall was 161 mm, recorded at Milford Sound on 2 December.
  • The highest wind gust was 176 km/hr, observed at South West Cape on 21 December.
  • Of the six main centres in December 2015, Auckland was the warmest and driest, Dunedin was the coolest and sunniest, Christchurch was the wettest and Hamilton was the cloudiest.
  • Of the available, regularly reporting sunshine observation sites, the sunniest four locations in 2015 (1 January to 31 December) were: Blenheim (2814 hours), Whakatane (2785 hours), Lake Tekapo (2737 hours) and Appleby (2731 hours). 

Download 

Download the December 2015 Montly Climate Summary [568KB PDF]

Climate Statistics for December 2015 [66KB PDF]

Contact

For further information, please contact:

Mr Chris Brandolino
Principal Scientist – Forecasting, NIWA National Climate Centre
Tel. 09 375 6335, Mobile (027) 886 0014