Anthony.. Of those various indices, I've been using the NOAA 3-month historical "Cold and Warm Episodes by Season" data. It seems to be the most popular. There is no ONI greater than 2.3. And, on an annual basis, either seasonal year or calendar year, 1987 was the warmest... +1.23 and 1999 the coldest, –1.13. On a seasonal year basis, Winter-Fall (DJF-SON) 2015 is already over of course...and it tied with 1997. The interesting thing (to me) is that 2015 started off strongly ahead of 1997 but faded after mid-year. So...When will we know if another strong La-Nina might come along? Looking back to 1997 the SST anomalies remained "warm" but started to decline in the winter (DJF) of 1998 and turned negative, cooler in MJJ of 1998. El-Nino didn't "recover". La_Nina took over until FMA of 2002. The overall trend since 1950 is essentially level. And, since 1987 the trend has been down through 2015.