During May 2019, the atmosphere continued to respond to a warm pool of water in the central and western Pacific, with above normal rainfall and cloud centred along and just west of the International Dateline. Rainfall and sea surface temperature (SST) patterns remained consistent with a weak, central Pacific El Niño.
However, there are signals that a trend towards ENSO-neutral conditions may occur toward the end of the JunetoAugustperiod. The NINO3.4 index SST anomaly for May was +0.72°C, which was a decrease for the second consecutive month.
The NINO1+2 index (in the far eastern Pacific) had an anomaly of +0.38°C, down nearly 0.20°C from last month. The Southern Oscillation Index (SOI) decreased to -0.7, compared with 0.0 for April. The conventional threshold for El Niño (SOI values below -1.0 for three consecutive months) has not been reached, but a weakly coupled central-based El Niño remains present.
According to the consensus from international models, the probabilityfor oceanic El Niño conditions is 66% for the June –August period. Beyond this, for the September –November period, the probability for oceanic El Niño conditions reducesto56%. For December 2019 to February 2020, El Niño remains the most likely outcome at 56%. This continues to suggest the occurrence of a ‘protracted’ weak event (multi-year duration).