Retrospective: September-November 2015 Outlook

During September – November 2015, above normal pressure was forecast over and to the south of Australia, while below normal pressure was expected to the east of New Zealand. 

This circulation pattern was likely to be accompanied with anomalous south-westerly winds.

Actual pressures were indeed higher than normal over Australia and the Tasman Sea while lower than normal pressures existed to the south-east of New Zealand. This pressure pattern produced a south-westerly flow anomaly.

Predicted air temperature: September – November 2015 temperatures were about equally likely to be average or below average for the North Island and in the north of the South Island. Mean temperatures were most likely to be in the below average range for the west and east of the South Island. 

Outcome: Actual temperatures were near average for the majority of the country. Pockets of below average temperature existed in Otorohanga, Masterton, South Wairarapa and parts of central Otago>

Predicted rainfall: September – November 2015 rainfall totals were most likely to be in the below normal range for the north and east of the North Island. Seasonal rainfall totals were about equally likely to be in the near normal or below normal range in the west of the North Island and the north and east of the South Island. Near normal rainfall was the most likely outcome for the west of South Island

Outcome: Actual rainfall was below normal in the west of the North Island and north and east of the South Island. Rainfall was also below normal in the districts of the Far North, Kaiapara, Whangarei, Buller, Grey, Mackenzie and Central Otago. Rainfall was near normal in Auckland, Hauraki, Waikato, Matamata-Piako Westland and Southland. Rainfall was above normal in Gisborne, Wairoa, Napier, Hastings and Central Hawke’s Bay.

Weather station. [NIWA]