Global setting: December 2015
Sea surface temperature anomalies in the central and eastern Pacific have weakened slightly, but still exceed +2oC.
The SOI is weakly negative at -0.6 for the month of December; however, strong westerly wind anomalies (weaker easterly trade-winds) continue to affect the western and central Pacific. Several ENSO indicators showed a weakening in the last two weeks, raising the possibility that El Niño could have reached its peak at the end of 2015. However, the current event is expected to remain in the strong category for the next three months, and the impacts of El Niño on New Zealand’s climate will likely persist into autumn.
International guidance indicates that El Niño conditions will continue (100% probability) over the next three months (January – March 2016) and will rapidly decay thereafter, with a return to normal conditions or a transition to La Niña conditions by July – September 2016.
For January - March 2016, above normal pressure is forecast to the north of New Zealand, while below normal pressure is expected to the south of the country. This circulation pattern is likely to be accompanied by anomalous westerly wind flows – a signature consistent with El Niño.
Sea surface temperatures
Sea surface temperatures are forecast to be below normal to the east of New Zealand.