June 2013 was characterised by lower pressures than normal across New Zealand and to the north and northeast of the country, with persistent high pressure centres south and southeast of Tasmania. This resulted in an anomalous east-southeasterly flow over the South Island, which contributed to well above normal rainfall totals recorded throughout areas to the east of the Southern Alps. Of particular note was the storm of 19-21 June, which brought the strongest sustained 10-minute winds that Wellington airport has seen since 1985. These strong winds resulted in widespread damage to infrastructure and vegetation in Wellington, and a loss of power for up to 30,000 homes. In addition, cold south-southeasterly winds associated with the storm resulted in a significant snowfall event across the South Island. Areas of the Mackenzie Country and the Maniototo bore the brunt of snowfalls, with unofficial reports of more than half a metre of snow there. Most South Island ski areas received in excess of one metre of new snow by the end of the storm, with Mt Hutt inundated by an estimated new snowfall total approaching three metres.
New Zealand Climate Update 169 – July 2013
What happened in June, how our climate outlook for the previous three months turned out, global and local sea temperatures, and our outlook for July to September.
The equatorial Pacific Ocean remains in a neutral state (neither El Niño nor La Niña). International guidance indicates that these neutral conditions are likely to persist for at least the coming three months (July–September). For the New Zealand region, higher pressures than normal are forecast south of the country, with slightly lower pressures than normal in the north Tasman Sea. This circulation pattern is likely to produce a weak easterly flow anomaly over the country.
Rainfall for the July–September period as a whole is likely to be normal or above normal in the east of the North Island, normal or below normal in the west and south of the South Island, and in the near normal range for all other regions.
Predicted rainfall: Rainfall is likely to be in the near normal range for all regions.
Outcome: Rainfall was above normal in Auckland, Waikato, Bay of Plenty, Taranaki, Wellington, Tasman, Marlborough, Canterbury and Otago regions. Normal rainfall few elsewhere.
Predicted air temperature: Temperatures are likely to be above average across the North Island, and are very likely to be above average across the South Island.