El Niño/Southern Oscillation (ENSO)

The tropical Pacific ocean remained in a neutral state (neither El Niño nor La Niña) in December 2013.

The western Pacific Ocean is still slightly warmer than normal but anomalies have declined compared to previous months.

The NINO4 sea surface temperatures (SST)index (in the western Pacific) is at 0.3°C for December 2013 (down from 0.5°C in November). NINO 3 value is 0 for the month of December 2013 and NINO 3.4 is weakly positive at +0.12°C (was +0.16°C in November).

The large area of higher than normal SSTs in the central east Pacific has been a persistent feature in the region for the past few months, and has extended further towards Fiji and intensified in December 2013.

Subsurface waters (i.e. between the surface and about 150m depth) are currently warmer than normal across the Pacific, with anomalies reaching more than 2°C in the eastern Pacific at 50m depth.

The trade winds are currently (as of 7 January 2014) close to normal. Convection and rainfall within the Intertropical Convergence Zone (ITCZ) was suppressed in the central and west Pacific.

The South Pacific Convergence Zone (SPCZ) was displaced north of its climatological position in December 2013.

The latest value for the TRMM ENSO index for the 30 days to 7 January is –1.07 (compared to –0.77 in November 2013).

The SOI is currently very close to zero (–0.1 in December).

The Madden – Julian Oscillation (MJO) was mostly inactive in the western Pacific in December. The MJO forecasts for the next two weeks indicate possible intensified intra-seasonal convective activity over the maritime continent and western Pacific.

The consensus forecast from IRI / CPC indicates that neutral ENSO conditions are extremely likely to persist over the January – March 2014 period, with 96 % chance, versus 2 % for La Niña and 2 % for El Niño.