Climate Summary for May 2016

Warmest May on record and plenty of rain for western regions.

Temperature	May temperatures were well above average (>1.20°C) for the entire North Island as well as the majority of the South Island. Pockets of above average temperatures (+0.51°C to +1.20 °C) were observed in Marlborough, Nelson, Tasman, the West Coast and Southland. No locations observed average temperatures (-0.50°C to +0.50°C) or colder than average temperatures.
Rainfall	Rainfall was well above normal (>149%) for large parts of the South Island. The exceptions were parts of central and eastern Canterbury were below normal (50-79%) and well below normal (<50%) rainfall was recorded.  In the North Island, rainfall was well above normal in Taranaki and Manawatu-Wanganui as well as the western portion of the Wellington region.  Well below normal rainfall was recorded along the coastal fringes of Gisborne, Hawke’s Bay and eastern Wellington.
Sunshine	Sunshine was below normal (75-89%) in the regions of Southland, the West Coast, Tasman, Manawatu-Wanganui and Taranaki. Above normal sunshine (110-125%) was recorded along the eastern portions of Gisborne, Hawke’s Bay and eastern Wellington. Sunshine was near normal in the regions of Waikato, Auckland and Northland.
Soil Moisture	As at 1 June 2016, soil moisture levels were below normal for the time of year for large parts of Gisborne, Hawke’s Bay, the Wairarapa as well as central and northern parts of Canterbury. Soil moisture levels for the remainder of the country were near normal for the time of year.

Video summary

In the video below NIWA Climate Scientist Nava Fedaeff reviews the month of May across New Zealand - a record-breaker for many.

Overview

During the month of May, air pressure was lower than normal over and to the south-west of the South Island while higher than normal pressures existed to the northeast of the country. This pressure set up led to a prevalence of north-westerly wind flow throughout the month. In addition to frequent north-westerlies, warmer than usual sea surface temperatures, particularly to the west of the country persisted throughout May. It is the combination of these two factors that contributed to the exceptional warmth felt across New Zealand throughout the month.  Virtually every climate station in New Zealand recorded well above average (>1.20°C) temperatures during May, with numerous locations experiencing record or near-record warmth (particularly in the North Island). The nationwide average temperature in May 2016 was 12.9°C [1](2.1°C above the 1981-2010 May average from NIWA’s seven station temperature series which begins in 1909), making May 2016 the warmest May on record using this series.  The first 5 months of 2016 have all been warmer than normal, and January-May 2016 is the equal warmest January-May period in the seven station temperature record (equalled by 1938).

While the warmer than normal seas surrounding New Zealand contributed to the warmth felt on land, they also provided added moisture or “fuel” to approaching storms. The second half of May saw a change in regime where a succession of low pressure systems travelling from west to east brought stormy and active weather. As a result, southern and western parts of the South Island as well as Taranaki, Manawatu-Wanganui and western Wellington received copious amounts of rain. For the month as whole, well above normal (>149%) rainfall was recorded in these areas, with some locations such as Palmerston North, Greymouth and Hokitika experiencing their wettest May on record.  The eastern fringes of Gisborne, Hawke’s Bay, eastern Wellington and the district of Kaikoura were sheltered from the north westerlies and passing lows and consequently received well below normal (<50%) rainfall in May. Mahia and Napier observed their 2^nd and 4^th driest May on record respectively.

Soil moisture

Soil moisture levels at the beginning of May were below normal for the time of year for large parts of New Zealand. The arrival of steady rain during the second half of May led to soil moisture levels gradually rising to near normal in southern Canterbury, Otago, Southland, the West Coast and western parts of the North Island. As at 1 June 2016, soil moisture levels remain below normal for the time of year for large parts of Gisborne, Hawke’s Bay, the Wairarapa as well as central and northern parts of Canterbury.

Sunshine

May sunshine hours were a reflection of the rainfall pattern seen during the month. The wettest parts of the country from Waikato down to Southland received below normal (75-89%) sunshine while the driest areas in May (coastal parts of Gisborne, Hawke’s Bay and eastern Wellington) experienced above normal sunshine (110-125%). Gisborne had its second sunniest May on record with records extending back to 1905. Sunshine was near normal in the Waikato, Auckland and Northland regions.

Further Highlights:

• The highest temperature was 27.6°C, observed at Kawerau on 9 May.
• The lowest temperature was -5.6°C, observed at Ranfurly on 25 May.
• The highest 1-day rainfall was 163.2 mm, recorded at North Egmont on 11 May.
• The highest wind gust was 174km/hr, observed at Cape Turnagain on 18 May.
• Of the six main centres in May 2016, Tauranga was the driest and sunniest, Auckland was the warmest, Dunedin was the coolest, Wellington was the wettest, and Hamilton was the cloudiest.
• Of the available, regularly reporting sunshine observation sites, the sunniest four locations in 2016 so far (1 January – 31 May) were Richmond (1289 hours), Blenheim (1167 hours), New Plymouth (1164 hours) and Takaka (1123 hours).

 

Download 

Download the May 2016 Montly Climate Summary [718.92 KB]

Climate Statistics for May 2016 [74 KB]

Contact

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