EL NIÑ O/SOUTHERN OSCILLATION (ENSO) DIAGNOSTIC DISCUSSION

issued by

CLIMATE PREDICTION CENTER/NCEP/NWS

and the International Research Institute for Climate and Society

 

9 October 2014

ENSO Alert System Status: El Niñ o Watch

Synopsis: El Niñ o is favored to begin in the next 1-2 months and last into the Northern Hemisphere spring 2015.

During September 2014, above-average sea surface temperatures (SST) continued across much of the equatorial Pacific (Fig. 1). The weekly Niñ o indices were relatively unchanged from the beginning of the month, with values ranging from +0.3° C (Niñ o-3.4) to +1.1° C (Niñ o-1+2) at the end of the month (Fig. 2). The change in subsurface heat content anomalies (averaged between 180º -100º W) was also minimal (Fig. 3) due to the persistence of above-average temperatures at depth across the central and eastern Pacific (Fig. 4). Equatorial low-level winds were largely near average for the month, though brief periods of westerly wind anomalies continue to arise. Upper-level winds were also close to average for the month. The Southern Oscillation Index has remained negative, and rainfall was near average around the Date Line, with a mix of positive and negative anomalies over Indonesia and Papua New Guinea (Fig. 5). The lack of coherent atmospheric and oceanic features indicates the continuation of ENSO-neutral.

Most models predict El Niñ o to develop during October-December 2014 and to continue into early 2015 (Fig. 6). The consensus of forecasters indicates a 2-in-3 chance of El Niñ o during the November 2014 - January 2015 season. This El Niñ o will likely remain weak (3-month values of the Niñ o-3.4 index between 0.5° C and 0.9° C) throughout its duration. In summary, El Niñ o is favored to begin in the next 1-2 months and last into the Northern Hemisphere spring 2015 (click CPC/IRI consensus forecast for the chance of each outcome).