The following weekly data and the first two images (of the Eq Pac Upper Ocean Heat Anom and the SSTA Evolution, respectively) were issued today by NOAA (for the week centered on April 19 2017), and the last two images where issued today by the BoM for the week ending April 23, 2017, showing the Nino 3.4 and the IOD, indices, respectively. Collectively, this information indicates that we are most likely beginning to transition from an ENSO neutral, into a weak El Nino pattern (assuming that the atmosphere follows the oceanic lead in the next few months).
Nino1+2 Nino3 Nino34 Nino4
Week SST SSTA SST SSTA SST SSTA SST SSTA
29MAR2017 27.8 1.8 28.1 0.8 27.7 0.3 28.3 0.0
05APR2017 26.7 0.9 28.2 0.8 27.9 0.3 28.3 0.0
12APR2017 26.1 0.5 28.2 0.7 28.0 0.2 28.5 0.0
19APR2017 26.4 1.1 28.1 0.6 28.3 0.5 28.8 0.3