For August – October 2017 as a whole, the atmospheric circulation around New Zealand was forecast to be characterised by lower pressure than normal west of the country, leading to weak northwesterly flow anomalies over New Zealand. La Niña-like atmospheric signals in the Pacific could result in intermittent periods of anomalous easterly or northeasterly flows. Significant low pressure systems, occasionally with a deep sub-tropical moisture connection, were also expected to sweep the country from time to time. Actual pressures were indeed lower than normal over and to the west of the country leading to more north westerlies than normal.
Predicted air temperature: August – October 2017 temperatures were forecast to be above average for all regions of New Zealand, with high confidence.
Outcome: Actual temperatures were above average for much of the country with small patches of near average temperatures about western Waikato, Marlborough and southern Southland.
Predicted rainfall: August – October 2017 rainfall totals were most likely to be near normal for the east of the South Island and near normal or above normal for all remaining regions of New Zealand.
Outcome: Actual rainfall was near normal for large parts of the country. Above normal rainfall was recorded in parts of the Bay of Plenty, South Taranaki, Marlborough and northern Canterbury. Below normal rainfall was observed in Southland and large parts of Otago.