Retrospective: October-December 2018 Outlook

The October – December 2018 atmospheric circulation around New Zealand was forecast to be characterized by higher pressure than normal to the west and southwest of New Zealand. This circulation pattern was expected to be associated with anticyclonic conditions extending over the country, interspersed by episodes of southerly and southwesterly winds. Actual pressures were near normal across the North Island and above normal over the South Island. This pressure set up led to more easterlies than normal for New Zealand.

Predicted air temperature: October – December 2018 temperatures were forecast to be average for all regions of New Zealand except the north of the South Island, where temperatures were forecast to be below average or near average.

Outcome: Actual temperatures were above average in Southland, the West Coast and parts of the Bay of Plenty and Manawatu-Whanganui. The remainder of the country saw near average temperatures.

Predicted rainfall: October – December 2018 rainfall totals were forecast to be below normal or near normal for all regions of New Zealand except the east of the North Island, where near normal rainfall was most likely.

Outcome: In the North Island, actual rainfall was above normal in Auckland and parts of Waikato, the Bay of Plenty, Hawke’s Bay and the Wairarapa. The remainder of the North Island saw near normal rainfall levels. In the South Island, the Marlborough, Canterbury and large parts of Otago saw above normal rainfall, while the remainder of the Island saw largely below normal rainfall.