Retrospective – August-October 2015 Outlook

During August – October 2015, above normal pressure was forecast over and to the south of Australia, while below normal pressure was expected well to the northeast of New Zealand.  This circulation pattern was likely to be accompanied with anomalous south-westerly winds, which is typical of an El Niño influence during winter-spring.

Actual pressures were higher than normal over the Australian Bight and extended over the Tasman and New Zealand. Mean sea level pressure south-east of New Zealand was lower than normal. This pressure set up produced more south westerlies than normal for the time of year. 

Predicted air temperature: August – October 2015 temperatures were about equally likely to be average or below average in all regions of New Zealand.

Outcome: Actual temperatures were near average for the majority of the country. Pockets of below average temperatures were recorded in Otorohanga, Masterton, Selwyn, Clutha and Stuart Island.

Predicted rainfall: August – October 2015 rainfall totals were forecast to be in the near normal or below normal range for all regions of New Zealand except for the west of the South Island, where near normal or above normal rainfall was expected.

Outcome: Actual rainfall was near normal for the majority of the North Island with the exception of Wairoa, Hastings and Central Hawke’s Bay where seasonal rainfall was above normal. In the South Island, rainfall was below normal in the north and east of the island and near normal in the west of the island. Clutha was the only district to experience above normal seasonal rainfall in the South Island.

Weather station. [NIWA]