Global setting: February 2017

The tropical Pacific is currently in an ENSO (El Niño – Southern Oscillation) neutral state (neither El Niño nor La Niña).

Sea surface temperatures (SSTs) in the central Equatorial Pacific Ocean are near average. However, during February, warming occurred across parts of the central and eastern equatorial Pacific, with the easternmost part of the equatorial Pacific observing its warmest sea-surface temperature anomalies since December 2015.

International guidance favours ENSO-neutral conditions with high probability (85% chance) over the next three month period (March – May 2017). Later during the year, models indicate significant chances for a return to El Niño conditions (over 50% in August – October 2017). As of 28 February, the Australian Bureau of Meteorology (BoM) ENSO tracker has been escalated to the “El Niño Watch” category. This means, according to the BoM, that the likelihood of El Nino forming in 2017 is approximately 50%.

However, over the next three months, with the likely persistence of ENSO-neutral conditions and intermittently active periods in the Madden-Julian Oscillation (pattern of increased or decreased rainfall and cloudiness along the equator that has a typical lifespan of 60 to 120 days) changeability in New Zealand’s weather patterns is likely to occur. The atmospheric circulation around New Zealand is expected to favour more westerly wind flows than normal.   

Sea Surface Temperatures

Water temperatures surrounding New Zealand are close to average to the west of the country and average or above average to the east. Along the immediate New Zealand coastline, sea surface temperatures (SSTs) are generally near or above normal for the time of year, especially in the east. The dynamical models’ forecasts for SSTs indicate that this pattern is likely to persist over the next three month period. Thus, coastal waters around the country are expected to be near average as a whole in March – May 2017.

Differences from average global sea surface temperatures for 19 February - 18 March 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: February SOI -0.2; December-February average 0.0.
Differences from average February surface temperatures in the seas around New Zealand