There is a 90% chance of forming El Nino in the Northern Hemisphere winter and a 60% chance to last until the Northern Hemisphere spring. ENSO-neutral state lasted during November, but in the last weeks, a positive anomalies occurred.
One possibility to measure the ENSO state (El Nino, neutral and La Nina) is the Oceanic Nino Index (ONI) which gives us information whether El Nino or La Nina are present. For El Nino, the index must be higher than or equal to 0.5 and for La Nina must be less than or equal to -0.5.
The index is counted as mean of three months and for now we have index 0.7 for the September, October and November mean. So watch out for the El Nino!