Climate Summary for April 2018

Two large storms bring destruction to parts of New Zealand

03 May 2018

Two large storms bring destruction to parts of New Zealand

Overview

Overall, April 2018 was characterised by lower pressure than normal over and to the southeast of New Zealand. Unlike the first three months of the year where La Niña conditions promoted more winds from a northeasterly direction, April’s pressure pattern resulted in more southwesterly winds than normal for much of the country. Several low pressure systems and cold fronts passed over New Zealand during April, bringing adverse weather to many locations. Storms occurring on the 10th-11th and 28th-29th days of the month were particularly damaging with the former bringing destructive winds and several tornados to some locations, while the latter brought heavy rain to parts of the country, resulting in flooding and the declaration of a state of emergency in Rotorua. Refer to the highlights and extreme events section for further details.

Despite the extreme weather events and southwesterly winds, stretches of calm weather were also observed for much of the country, notably the first week of the month as well as the 19th – 25th days of the month. This resulted near average (-0.50 to +0.50°C) April temperatures overall for large parts of of both Islands and even above average (+0.51 to +1.20°C of average) for many parts of the North Island. Parts of the central and southwestern South Island however, experienced below average (-0.50°C to ‑1.20°C of average) temperatures for April as a whole.

The nationwide average temperature in April 2018 was 13.3°C (0.1°C above the 1981-2010 April average from NIWA’s seven station temperature series which begins in 1909).

Further Highlights

  • The highest temperature was 28.5°C, observed at Napier on 4 April.
  • The lowest temperature was -4.9°C, observed at Ranfurly on 14 April.
  • The highest 1-day rainfall was 133 mm, recorded at Te Puke on 15 April.
  • The highest wind gust was 161 km/h, observed at Akitio on 20 April.
  • Of the six main centres in April 2018, Dunedin and Auckland were the wettest, Hamilton was the driest, Auckland was the warmest, Christchurch and Dunedin were the coolest, Tauranga was the sunniest, and Dunedin was least sunny.
  • Of the available automatic sunshine observation sites, the sunniest four regions in 2018 so far (1 January – 30 April) are Wider Nelson (898 hours), Marlborough (896 hours), Hawke’s Bay (887 hours) and Canterbury (873 hours).

Contact

Mr Chris Brandolino, Principal Scientist – Forecasting, NIWA National Climate Centre Tel. 09 375 6335, Mobile 027 866 0014

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