El Niño/Southern Oscillation (ENSO)

The tropical Pacific remained in a neutral state (neither El Niño nor La Niña) in March 2013. Between February and March 2013, the pattern of anomalous sea surface temperatures (SSTs) with slightly warmer than normal SSTs in the West and cooler than normal SSTs in the east weakened.

The region of warmer than normal SSTs south of Australia intensified and extended eastward towards the South Island of New Zealand (reaching more than +1.5°C).

March NINO values are 0.03°C for NINO3.4 (up from –0.33°C in February 2013), 0.3°C for NINO3 (up from –0.06°C in February 2013) and –0.04°C for NINO4 (up from –0.09°C in February 2013). Warmer than normal subsurface temperatures still exist along the Equator at about 150m depth west of the Dateline.

The trade winds are currently slightly stronger than normal in the central and west Pacific, and slightly weaker than normal in the eastern Pacific, but remain within the normal range.

The Intertropical Convergence Zone (ITCZ) was close to its climatological position and intensity in March. The South Pacific Convergence Zone (SPCZ) was well defined, with more intense rainfall than normal west of the Dateline and a position well southwest of climatology east of the Dateline.

The latest value for the TRMM ENSO index for the 30 days to April 2nd is 0.22 (on El Niño side of neutral) and the monthly SOI for March is +1.

The Madden – Julian Oscillation was positioned over West Africa in March and is forecast to slowly move eastward over the coming two weeks, it is not expected to bring enhanced convective activity over the region in the coming weeks.

The international consensus indicates that neutral ENSO conditions are very likely to persist over the April – June 2013 period. 

Surface temperature anomalies (ºC) for March 2013, 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).