During August 2014, above-average sea surface temperatures (SST) continued across much of the equatorial Pacific (Fig. 1). Most of the Niño indices warmed during the month with values of +0.5oC in Niño-4, +0.4oC in Niño-3.4, +0.4oC in Niño-3, and +0.8oC in Niño-1+2 (Fig. 2). Subsurface heat content anomalies (averaged between 180o-100oW) also increased during the month (Fig. 3) as above-average subsurface temperatures developed across the central and east-central equatorial Pacific (Fig. 4). This warming is associated with the downwelling phase of an equatorial oceanic Kelvin wave triggered in July by low-level westerly wind anomalies. Westerly wind anomalies continued in the central and eastern part of the basin early in August, but weakened by the end of the month. Enhanced easterly upper-level wind anomalies have prevailed during much of the month, and the Southern Oscillation Index has been negative. However, convective cloudiness remained generally near average over most of the region, except for below average cloudiness observed across the central and western Pacific (Fig. 5). The lack of a coherent atmospheric El Niño pattern and near-average SSTs in the central Pacific indicate a continuation of ENSO-neutral.
Most of the models continue to predict El Niño to develop during September-November and to continue into early 2015 (Fig. 6). A majority of models and the multi-model averages favor a weak El Niño. At this time, the consensus of forecasters expects El Niño to emerge during September-October and to peak at weak strength during the late fall and early winter (3-month values of the Niño-3.4 index between 0.5oC and 0.9oC). The chance of El Niño is at 60-65% during the Northern Hemisphere fall and winter.
