Synopsis: A transition to ENSO-neutral is expected to occur by February 2017, with ENSO-neutral then continuing through the first half of 2017. La Niña continued during December, with negative sea surface temperature (SST) anomalies continuing across the central and eastern equatorial Pacific. The weekly Niño index values fluctuated during the last month, with the Niño-3 and Niño-3.4 regions hovering near and slightly warmer than -0.5°C. The upper-ocean heat content anomaly was near zero when averaged across the eastern Pacific, though near-to-below average subsurface temperatures were evident closer to the surface. Atmospheric convection remained suppressed over the central tropical Pacific and enhanced over Indonesia. The low-level easterly winds were slightly enhanced over the western Pacific, and upper-level westerly anomalies were observed across the eastern Pacific. Overall, the ocean and atmosphere system remained consistent with a weak La Niña. The multi-model averages favor an imminent transition to ENSO-neutral (3-month average Niño-3.4 index between -0.5°C and 0.5°C), with ENSO-neutral lasting through August-October (ASO) 2017. Along with the model forecasts, the decay of the subsurface temperature anomalies and marginally cool conditions at and near the ocean surface portends the return of ENSO-neutral over the next month. In summary, a transition to ENSO-neutral is expected to occur by February 2017, with ENSO-neutral then continuing through the first half of 2017. Even as the tropical Pacific Ocean returns to ENSO-neutral conditions, the atmospheric impacts from La Niña could persist during the upcoming months.
Almost all of the North Island should be slightly to moderately cooler than normal.
Slightly to moderately drier than normal for most of the North Island and near normal in Hawkes Bay and East Cape.
Moderately cooler than normal in the west and near and near normal in the east.
Moderately drier in the west and slightly drier in the central areas and near normal in the eastern third of the island.