El Niño/Southern Oscillation (ENSO)
El Niño conditions continued in the Tropical Pacific during March 2016, but the current event has clearly entered its decaying phase.
Sea surface temperature (SST) anomalies in the central and eastern Equatorial Pacific weakened further in March, with all NINO SST indices well below the +2oC mark. Sub-surface ocean temperature anomalies across the eastern Pacific have weakened and shoaled substantially and now barely exceed +2oC in the first ~50m of the ocean east of about 130oW, while deeper cooler waters have spread eastward from the western Pacific. These changes in sub-surface temperatures make it very likely that the current SST anomalies will retreat further towards average in the next few months. Meanwhile, the Southern Oscillation Index (SOI) also weakened over March 2014, with a value for March as a whole of -0.4.
The strong westerly wind anomalies (weaker easterly trade-winds) that dominated the western and central Pacific until the beginning of 2016 have now almost dissipated. While convective activity and rainfall remains higher than normal in the Equatorial central and eastern Pacific, the dry conditions that affected the Maritime Continent have weakened significantly. The South Pacific Convergence Zone (SPCZ) was more intense than normal in the south eastern Pacific. The ENSO Precipitation Index (ESPI) reflects El Niño conditions with a value of +0.8 (value to the 6th of April 2016), a sharp decrease compared to previous months.
The Madden-Julian Oscillation (MJO) was weak in the western Pacific over March as a whole. At the horizon of 14 days, the CPC forecasts indicate overall low chances of increased intra-seasonal convective activity in the western Pacific. International guidance indicates that El Niño conditions are very likely (80% chance) to continue over the next three months (April – June 2016) as a whole, but all models forecast El Niño to weaken further over the same period. A return to normal conditions (49% chance) or a transition to La Niña (40% chance) is expected by July – September 2016. La Niña conditions become increasingly likely towards the end of 2016 (over 45% chance for October – December 2016).