The November Nino34 region SSTA was around -0.8C easily cooler than the -0.5C La Nina threshold. During September and October Nino34 SSTA was slightly warmer than the La Nina threshold. Usually NOAA prefers 3 consecutive months reaching the threshold before declaring onset of an ENSO event. However, given the reasonably well developed La Nina in-place Climate Impact Company anticipates an official declaration by NOAA of La Nina onset in their December ENSO update.
The best analog years somewhat representative of the past 12 months and similar to this time of year are 1984, 1999 and 2011. In the 12 months that followed the analog years agree that a moderate La Nina occurred during northern hemisphere winter and La Nina lasted through the following spring. Previously, La Nina was expected to be weaker and dissipate more quickly. Depicted by the analog forecast is a stronger La Nina scenario.
Previous forecasts also speculated El Nino could generate later next year. The analog projection returns ENSO to neutral phase next summer and instead of an El Nino trend reverses ENSO phase to weak La Nina later next year.
Pictured: Effects of a La Nina climate.