El Niño/Southern Oscillation (ENSO)

The equatorial Pacific Ocean remains warmer than normal, especially over and west of the Dateline. 

Atmospheric circulation is close to normal for this time of the year. Sea surface temperature anomalies have shown relatively little change along the Equator.

The NINO4 index (150 °W – 160 °E) is still the warmest of all NINO indices (+ 1°C up from + 0.8 °C in October) and both the NINO3 and NINO3.4 indices are in the neutral range (+ 0.2 and + 0.4°C respectively).

Warmer than normal subsurface temperature anomalies exist along the Equator at about 100m depth, but the surface expression is weak and heat content in the upper ocean (0 to 300 m) is currently close to normal.

Surface winds along the Equator are also close to climatology. Convection and rainfall are still anomalously high just north of the Equator, to the west of the Dateline, indicating an ITCZ south of normal.

The SPCZ switched from a very zonal orientation (positioned around 10°S) in October to a position south of normal, extending from the vicinity of Vanuatu to the subtropical central Pacific.

The latest value for the TRMM ENSO index for the 30 days to December 2nd is –0.11 (neutral) and the monthly SOI for November is + 0.38 (on La Niña side of neutral).

A weak Madden – Julian Oscillation moved into Australasian longitudes over the last two weeks of November but is forecast to weaken further as it propagates eastward.

Based on the climate models that NIWA monitors and the international consensus, El Niño development during the summer is unlikely. The forecast is for neutral conditions to persist over the summer, with sea surface temperatures remaining generally warmer than average along the Equator. 

Surface temperature anomalies (ºC) for November 2012, data is from the NOAA OISST Version 2 dataset, available at the NOAA’s Climate Data Center (ftp.cdc.noaa.gov/Datasets/noaa.oisst.v2.highres).