Global setting: October 2018
The November 2018 – January 2019 atmospheric circulation around New Zealand is forecast to be characterised by higher pressure than normal around the country and lower pressure than normal to the southwest. Frequent high pressure systems are expected around and over the country during November. For the three month period (November 2018 – January 2019) as a whole, westerly quarter air flow anomalies are expected, though periodic easterly quarter air flows are possible.
The consensus from international models is for the tropical Pacific to transition towards El Niño over the next three-month period (88% chance over November 2018 – January 2019). The probability for El Niño remains high through autumn 2019, with a 88% chance for El Niño conditions over the March – May 2019 period, with some long-range models indicating the possibility of the event continuing through next winter in the Southern Hemisphere (a protracted El Niño event).
Sea Surface Temperatures
The expectation for warmer than average air temperatures during November will likely result in the continuation of warmer than average SSTs for at least the start of the coming three month period. Thereafter, dynamical models suggest that SSTs are likely to remain above average or near average into the summer season.