El Niño/Southern Oscillation (ENSO)

The equatorial Pacific Ocean remains close to El Niño thresholds, but the atmosphere has yet to show any significant response to the warmer than normal sea surface temperatures.

Sea surface temperature anomalies have weakened significantly in the eastern Pacific but have shown little change near the dateline.

The NINO3 index has dropped to + 0.2 °C (from + 0.7 in September) and NINO4 (150 °W – 160 °E) is currently the warmest of all NINO indexes at + 0.8 °C.

Heat content in the upper ocean (0 to 300 m) is generally positive near to and west of the dateline. The TAO analyses show that a warmer than normal subsurface temperature anomaly persists along the Equator at about 100m depth and is slightly more coherent compared to September.

Surface winds along the Equator are currently very close to normal. Convection and rainfall are still anomalously high south of the Equator, to the west of the Dateline.

The ITCZ and the SPCZ are both displaced equatorward and the SPCZ had a very zonal orientation (positioned around 10°S) in October.

The latest value for the TRMM ENSO index for the 30 days to November 1st is –0.11 (i.e. neutral) and the monthly SOI for October is + 0.3, (i.e. on La Niña side of neutral).

A Madden – Julian Oscillation (MJO) event was related to enhanced convection in the Indian Ocean and decreased convection over the maritime continent during the last two weeks, and is forecast to slowly move eastward and weaken during the first two weeks of November.

Based on the climate models that NIWA monitors and the international consensus, there is an approximately 50:50 chance of neutral versus weak El Niño conditions over the period November 2012 – January 2013. 

Surface temperature anomalies (°C) for October 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).