The atmospheric circulation around New Zealand was forecast to favour more anticyclonic flows (high pressure) than normal to start the three month period of June – August 2017, bringing extended periods of settled weather.
September – November 2017 temperatures are forecast to be above average for all regions of New Zealand (55% to 65% chance for above average temperatures).
ENSO (El Niño – Southern Oscillation) neutral conditions were still present in the tropical Pacific during August 2017.
Overall, mean sea level pressure was lower than normal over and to the west of New Zealand during August while higher than normal mean sea level pressure occurred offshore to the east
During May-July, the atmospheric circulation around New Zealand was forecast to favour slightly more south-westerly flows than normal, but variable circulation regimes were to be expected over the course of the season.
August – October 2017 temperatures are forecast to be above average for all regions of New Zealand, with high confidence (55-70% chance for above average temperatures). Nevertheless, frosts and cold snaps will occur during the remainder of winter and in early spring. Coastal water temperatures around New Zealand are forecast to remain above average over the next three-month period.
ENSO (El Niño – Southern Oscillation) neutral conditions (neither El Niño nor La Niña) continued in the tropical Pacific during July 2017, but this month mixed signals were again present. In particular, some atmospheric patterns have been recently leaning more towards weak La Niña conditions.
July was a tumultuous month due to the passage of several active low pressure systems and consequently there were numerous high impact weather events throughout the month
During April-June, the atmospheric circulation around New Zealand was expected to favour higher pressure than normal to the west of the country, with more anticyclonic south-westerly wind flows than normal, a pattern suggestive of El Niño.
July – September 2017 temperatures are about equally likely to be above average (45% chance) or near average (40% chance) for the west and east of the North Island.
The tropical Pacific remained in an ENSO (El Niño – Southern Oscillation) neutral state (neither El Niño nor La Niña) during June 2017, but oceanic and atmospheric anomalies were mixed, with some indicators leaning towards El Niño and others towards La Niña.
Overall, mean sea level air pressures were higher than normal over and to the east, west, and south New Zealand during June.
During March-May, the likely persistence of ENSO-neutral conditions and intermittently active periods in the Madden-Julian Oscillation, changeability in New Zealand’s weather patterns was expected to occur.