Global setting: December 2016

The tropical Pacific continues to exhibit mainly ENSO-neutral conditions. Sea surface temperatures (SSTs) in the central Equatorial Pacific Ocean remain marginally below average.

In the sub-surface ocean, the pockets of cooler than average temperatures that were present in November 2016 have contracted and warmed. Thus, it appears that any La Niña-like oceanic signal has peaked and is subsiding back toward neutral. The atmospheric setup is mixed as stronger easterly trade winds in the central Pacific along with enhanced convection over parts of the Maritime Continent are consistent with La Niña conditions. The Southern Oscillation Index (SOI) is weakly positive and is consistent with ENSO-neutral conditions. 

International guidance now strongly favours ENSO-neutral conditions (77% chance) over the next three month period (January - March 2017). By March-May 2017, the chance for neutral conditions rises to 87% with a meagre 8% chance for El Niño conditions and 5% chance for La Niña conditions. In summary, ENSO-neutral conditions are likely over the next 3-month period and should continue into autumn.

Consequently, the combination of ENSO-neutral conditions, along with the absence of other large-scale climate drivers for the remainder of summer into early autumn, may result in only weak air flow anomalies. Mostly typical summer conditions are expected with high pressure systems crossing the North Island and prevailing westerly winds over the South Island

Sea Surface Temperatures

Sea surface temperatures around New Zealand are expected to be near average or above average over the next three months.

Differences from average global sea surface temperatures for 11 December - 7 January 2017. Map courtesy of NOAA Climate Diagnostics Centre (http://www.esrl.noaa.gov/psd/map/images/sst/sst.anom.month.gif)
Monthly values of the Southern Oscillation Index (SOI), a measure of changes in atmospheric pressures across the Pacific, and the 3-month mean (black line). SOI mean values: December SOI 0.2; October to December average -0.1.
Differences from average December surface temperatures in the seas around New Zealand.