Retrospective: November – January 2018 Outlook
For November 2017 – January 2018 as a whole, the atmospheric circulation around New Zealand was forecast to be characterized by higher pressure than normal to the south-east of the country, and lower pressure than normal to the north. This pressure pattern was expected to be associated with north-easterly to easterly flow anomalies, a pattern consistent with regional conditions typically observed during La Niña events. Actual pressures were higher than normal over New Zealand and in particular to the south-east of the country. This pressure set up led to more easterly quarter winds than normal as forecast.
Predicted air temperature: November 2017 – January 2018 temperatures were forecast to be above average for all regions of New Zealand.
Outcome: Actual temperatures were well above average for much of the country with the exception of Gisborne and the Mahia peninsula where above average temperatures were observed.
Predicted rainfall: November 2017 – January 2018 rainfall totals were about equally likely to be normal or above normal for the north and east of the North Island, and most likely to be near normal in the west of the North Island and the north and east of the South Island. Below normal or near normal rainfall was forecast in the west of the South Island.
Outcome: Actual rainfall was near normal for parts of Northland, Waikato, Bay of Plenty, Manawatu-Whanganui, Tasman and Marlborough. Small pockets of above normal rainfall were observed in Nelson and Tasman. Below normal rainfall was recorded for the rest of the country.