Island Climate Update 218 - November 2018

Sea surface temperatures (SSTs) in the central Pacific (NINO3.4 Index) warmed notably over the past month, increasing from an anomaly of +0.25°C in September to +0.75°C in October. The anomaly value for October exceeded what international centres consider necessary for the onset of El Niño conditions. The NINO1+2 Index in the eastern Pacific (near South America) continued to show significant variability. This pattern of SST anomalies continues to be consistent with the expected development of El Niño ‘Modoki’, a non-conventional type where the maximum SST anomaly is located in the central Pacific rather than the eastern Pacific. 

Warmer than average subsurface ocean waters strengthened and expanded eastward during October. Anomalies of +3.0°C and above now cover a wide area from the Dateline to 100oW at 150m depth in the west and 50m depth in the east. This is associated with large upper-ocean heat content anomalies (+1.5 to 2.0°C), spanning from near the Dateline to about 110°W.

The Southern Oscillation Index (SOI) was slightly positive with a value of +0.2 for October 2018, following negative values during August and September.

The consensus from international models is for the tropical Pacific to transition towards El Niño over the next three-month period (88% chance over November 2018 – January 2019). The probability for El Niño remains high through autumn 2019, with a 88% chance for El Niño conditions over the March – May 2019 period, with some long-range models indicating the possibility of the event continuing through next winter in the Southern Hemisphere (a protracted El Niño event).

Download the report: Island Climate Update November 2018 [3.27MB PDF]