I was notified today of the rather remarkable plume of ENSO forecasts for 2015 from ECMWF (European Centre for Medium-Range Weather Forecasts). See their System 4 ENSO region sea surface temperature anomaly forecast webpage here.
Figure 1 presents the ECWMF plume of sea surface temperature anomaly forecasts for the NINO3 region (5S-5N, 150W-90W), with some of the runs reaching highs in November 2015 in the neighborhood of +4.5 deg C.
For those unfamiliar with them, see the map of NINO regions here.
Figure 2 show the plume for the NINO3.4 region (5S-5N, 170W-120W). Note how a couple of the runs reach beyond the upper +4 deg C extent of the y-axis.
Now consider that NINO3.4 sea surface temperature anomalies peaked at +2.7 deg C in December 1997 in response to the 1997/98 super El Niño, and peaked at +2.8 deg C in January 1983 during the 1982/83 El Niño. See Figure 3, which is from the April 2015 Sea Surface Temperature (SST) Anomaly Update.
ARE NOVEMBER SEA SURFACE TEMPERATURE ANOMALIES OF +4.0 DEG C AND HIGHER IN THE NINO3.4 REGION PHYSICALLY POSSIBLE?
In the post Why Do El Niño and La Niña Events Peak in Boreal Winter?, we illustrated and discussed how and why the sea surface temperatures (absolute) of the NINO3.4 region mimic the seasonal cycle of, and come near to the values of, those in the western equatorial Pacific (5S-5N, 120E-165E) during a strong El Niño, like the one in 1997/98.
Based on the Reynolds OI.v2 data, the average November sea surface temperatures for the NINO3.4 region for the period of 1981-2010 is 26.64 deg C. That value serves as the November reference temperature for NINO3.4 sea surface temperatures anomalies.
Sea surface temperatures in the western equatorial Pacific (5S-5N, 120E-165E) are naturally warmer than those of the NINO3.4 region. The November sea surface temperature for the western equatorial Pacific in 2012 was 29.95 deg C; in 2013 the temperature there was 29.98 deg C; and, for 2014, it was 29.90 deg C. The average November temperature for the western equatorial Pacific for the past 3 years was about 29.94 deg C.
Let’s assume for a moment that the sea surface temperatures in NINO3.4 region did something very unusual in November 2015 and rose to that 2012-2014 average value of the western equatorial Pacific of 29.94 deg C. The November 2015 NINO3.4 sea surface temperature anomaly would be 3.3 deg C. That’s far short of 4 deg C.
Because someone’s bound to ask, in November 1997, the sea surface temperature for the western equatorial Pacific was 29.35 deg C, while the NINO3.4 region was remarkably similar at 29.31 deg C. And for November 1982, the sea surface temperature for the western equatorial Pacific was 29.08 deg C, while the NINO3.4 region was a little less at 28.81 deg C.
[My thanks for the heads-up, anonymous person.]
The Reynolds OI.v2 sea surface temperature data are available from the KNMI Climate Explorer.