Retrospective: September-November 2018 Outlook

The September – November 2018 atmospheric circulation around New Zealand was forecast to be characterized by higher pressure than normal over the South Island and to the south and west of the country and lower than normal pressure to the northeast of New Zealand, leading to anomalous easterly quarter (southeast to northeast) air flows over New Zealand. This deviates from the enhanced southwesterly air flow pattern typically experienced during traditional El Niño events. Actual pressures were higher than normal across the country and particularly to the south of New Zealand. This pressure set up lead to more southeasterlies than normal.

Predicted air temperature: September – November 2018 temperatures were forecast to be average or above average for all regions of New Zealand except the north and east of the North Island, where near average temperatures are most likely.

Outcome: Actual temperatures were near average for virtually the whole country. Small pockets of slightly below average temperatures were found in coastal Canterbury.

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

Outcome: Actual rainfall was below normal for the north and west of the North island and the north of the South Island. A wet November meant that rainfall was above normal for the season for the east of the South Island and Otago. Rainfall was near normal along the West Coast and large parts of Southland. Rainfall was also near normal for the east of the North island with the exception of Hawke’s Bay where above normal rainfall was observed.