For July – September 2017, the atmospheric circulation around New Zealand was forecast to be characterised by slightly higher than normal pressures southeast of the Chatham Islands, leading to weak easterly-quarter flow anomalies over the country. Actual pressures were lower than normal over and to the west of the country. This lead to more westerly to north-westerly wind flows than normal.
Predicted air temperature: July – September 2017 temperatures were forecast to be near or above average for the west and east of the North Island, and above average, with high confidence, for all remaining regions of New Zealand.
Outcome: Actual temperatures were above average for large parts of Waikato, Bay of Plenty, Gisborne, Hawke’s Bay and the West Coast. Temperature was near average elsewhere.
Predicted rainfall: July – September 2017 rainfall totals were forecast to be near or above normal for the east of the North Island, and near normal for the remaining regions of the country.
Outcome: Actual rainfall was above normal for western Northland and Auckland as well as large parts of Waikato, the Bay of Plenty, Taranaki, Manawatu-Whanganui, Wellington, Tasman, Nelson, Marlborough, Canterbury and Otago. Rainfall was below normal about coastal Gisborne, Hastings and Invercargill and near normal elsewhere.