Thanks for your detailed explanation. I also greatly enjoyed your talk at the ENSO conference at Columbia. My question: how is the ONI 3 month average calculated? For example, the ONI for ASO 2015 is 1.7 BUT the monthly data for 3.4 are respectively: Aug 2.07; Sep 2.28; Oct 2.46. Clearly the average of these three numbers is not 1.7. I'm sure I'm missing something obvious here but haven't been able to find an explanation. Belinda