At the surface in the eastern equatorial Pacific the latest weekly SSTA analysis provided by the Bureau of Meteorology/Australia indicates the cool La Nina signature has faded and neutral ENSO is now in-place (Fig. 1). The first quarter of 2018 has featured a mostly neutral southern oscillation index (SOI) also representative of a fading ENSO event (Fig. 2). In the subsurface of the equatorial eastern Pacific dramatic warming at depth has taken place as a Kelvin Wave pushes east of the Dateline (Fig. 3). In the far eastern equatorial Pacific subsurface cool fuel to sustain La Nina is fading.
The eastward progression of the Kelvin Wave is further evidence of La Nina’s demise. If the Kelvin Wave were to interact with a transient Madden Julian oscillation (MJO) significant warming of the equatorial East Pacific would occur during northern hemisphere spring. However, at the moment, operational models forecasting MJO do not indicate this possibility.
Therefore the ENSO forecast for 2018 favors neutral phase. The Bureau of Meteorology/Australia indicates the Nino34 SSTA region is near neutral (Fig. 4) for the length of the forecast (through December 2018). Climate Impact Company has assembled an analog forecast of ENSO extending into 2019 also indicating neutral ENSO phase is likely (Fig. 5).
Forecast confidence is reasonable that developing El Nino or returning La Nina is unlikely in 2018.
Fig. 1: Bureau of Meteorology/Australia Pacific SSTA analysis identifies fading cool anomalies in the eastern equatorial Pacific indicating La Nina has ended.
Fig. 2: Bureau of Meteorology/Australia southern oscillation index observations indicate mostly neutral ENSO character in 2018.
Fig. 3: The equatorial subsurface across the East Pacific is warming dramatically at depth while lingering cool fuel for La Nina is fading.
Fig. 4: The Bureau of Meteorology/Australia Nino34 SSTA forecast indicates neutral phase for 2018.
Fig. 5: The Climate Impact Company ENSO analog forecast for 2018-19 also indicate neutral ENSO ahead.