August 2014 Climate Summary

Full summary: Climate_Summary_August_2014.docx

Highly variable rainfall but plenty of sunshine

Overview

August 2014 was characterised by anomalously high pressure south of Australia extending over and around New Zealand. This pressure pattern brought about strong south-westerly flow anomalies to the country.

Rainfall during August was highly variable across the country. Above normal rainfall (120-149%) occurred throughout eastern Northland, Manawatu-Wanganui, Gisborne and Southland regions as well as the Central Otago and Mackenzie districts. The largest rainfall anomalies were in Whangarei and Gisborne where rainfall in excess of 200% of normal occurred. In contrast, dry conditions prevailed in the Waikato, Bay of Plenty, and the north of the West Coast where below normal rainfall (50-79%) was experienced. Conditions were even drier in Tasman, Nelson, Marlborough and coastal Canterbury where well below normal rainfall (< 50%) was observed. As a result, several sites in these regions experienced near-record low rainfall totals for the month.

A lack of rain in large parts of the country coincided with a very sunny end to winter with well above normal (>125%) or above normal (110-125%) sunshine recorded for many locations. It was particularly sunny in the Waikato, Bay of Plenty, Westland, southern Canterbury and Central Otago where well above normal sunshine was observed and several August records were set. Only two locations (Takaka and Martinborough) recorded below normal sunshine levels during August.

Soil moisture levels around the country were at field capacity at the start of August 2014 but began to deplete during the second half of the month. Despite this, as at 1 September soil moisture levels in most parts of the country remained within the near normal range for the time of year but were slightly drier than normal in Taranaki, the West Coast and Tasman as well as the districts of Selwyn, Waimakariri and Timaru.

The near average temperatures observed in July continued into August, with the majority of the country characterised again by near average temperatures (within 0.5°C of average). In fact nationwide, only a handful of stations reported above average mean temperatures for August. Small pockets of below average temperature (-1.20 to -0.51°C) were recorded in the districts of Waitomo, Opotoki, Central Hawke’s Bay, Tararua and South Wairarapa. Despite the fairly neutral August mean temperatures, some weather highlights did occur. In particular the 1st-3rd of August were exceptionally warm all around the country due to a north-westerly flow combined with the foehn effect in eastern areas. As a result, several locations experienced record or near record high daily maximum and minimum temperatures. The nation-wide average temperature in August 2014 was 8.7°C (0.1°C above the 1971-2000 August average from NIWA’s seven station temperature series which begins in 1909) [interim value].

Further Highlights:

• The highest temperature was 23.6°C, observed at Christchurch (Riccarton) on 2 August.

• The lowest temperature was -7.0°C, observed at Middlemarch on 4 August.

• The highest 1-day rainfall was 157.2 mm, recorded at Tolaga Bay on 4 August.

• The highest wind gust was 189 km/hr, observed at Cape Turnagain on 8 August.

• Of the six main centres in August 2014, Christchurch was the coolest and driest, Auckland was the warmest, wettest and cloudiest and Tauranga was the sunniest.

• Of the available, regularly reporting sunshine observation sites, the sunniest four centres so far in 2014 (January to August) are: Whakatane (1793 hours), Tauranga (1622 hours), Nelson (1557 hours) and Lake Tekapo (1554 hours).

Full summary: Climate_Summary_August_2014.docx

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