Synopsis: ENSO-Neutral conditions are slightly favoured (between 55-60%) during the upcoming Northern Hemisphere fall and winter 2016-17.
ENSO-Neutral conditions were observed over the past month, although sea surface temperatures (SSTs) were below-average over the east-central equatorial Pacific Ocean. While the Niño-3.4 and Niño-3 regions remained around -0.5°C for most of the month, Niño-4 and Niño 1+2 were -0.1°C and +0.3°C, respectively, by the end of the month. Subsurface temperatures across the eastern and central Pacific remained below average, and negative temperature anomalies remained weak across the western Pacific. Atmospheric anomalies over the tropical Pacific Ocean largely indicated ENSO-Neutral conditions. The traditional Southern Oscillation index and the equatorial Southern Oscillation index were weakly positive during August. The lower-level winds were near average, while the upper-level winds were anomalously westerly in a small region to the east of the International Date Line. Convection was suppressed over the western and central tropical Pacific, although less suppressed compared to last month. Overall, the combined ocean and atmosphere system continues to reflect ENSO-Neutral.
The multi-model averages favour borderline Neutral-La Niña conditions (3-month average Niño-3.4 index less than or equal to -0.5°C) during the Southern Hemisphere spring, continuing into summer. However, the more recently updated model runs from the North American Multi-Model Ensemble (NMME) more strongly favour ENSO-Neutral. The forecaster consensus prefers this outcome, which is supported by the lack of significant anomalies in several indicators over the past month (winds, convection, subsurface temperatures). Overall, ENSO-Neutral conditions are slightly favoured (between 55-60%) during the upcoming Southern Hemisphere spring and summer 2016-17.
Almost all of the North Island should be slightly warmer than normal.
Near normal to slightly to moderately wetter than normal from Northland along the entire east coast of the North Island with near normal to slightly drier than normal conditions across most of the Waikato through to Wellington.
Almost all of the South Island should be slightly to moderately warmer than normal.
Moderately to severely drier in the western half of the island and near normal to slightly wetter and in isolated placed moderately wetter than normal in the eastern half.