Near-to-above average sea surface temperatures (SSTs) were observed in the east-central tropical Pacific Ocean during October [Fig. 1]. In the most recent week, the SST indices in the westernmost Niño-4 and Niño-3.4 regions were +0.7°C and +0.5°C, respectively, while farther east in the Niño-3 and Niño-1+2 regions they were near-to-below average (+0.3°C and -0.6°C respectively; [Fig. 2]). The subsurface temperature anomalies (averaged across 180°-100°W) were above average during the month [Fig. 3] as a downwelling oceanic Kelvin wave that began in September continued progressing eastward into the eastern Pacific [Fig. 4]. Low-level winds were near average during October, while easterly upper-level wind anomalies were observed over the eastern Pacific. Finally, tropical convection was suppressed near the Date Line and also over Indonesia, while somewhat enhanced convection prevailed over the western Pacific, northeast of Papua New Guinea [Fig. 5]. Overall, despite the recent anomalous warming across the east-central equatorial Pacific, the overall oceanic and atmospheric system reflected ENSO-neutral.
The majority of models in the IRI/CPC plume [Fig. 6] continue to favor ENSO-neutral (Niño-3.4 index between -0.5°C and +0.5°C) through the Northern Hemisphere spring. Many dynamical forecast models, including the NCEP CFSv2, suggest Niño-3.4 SST index values will remain near +0.5°C during November before decreasing toward zero. Forecasters believe this recent warmth reflects sub-seasonal variability and is not indicative of an evolution toward El Niño. The chances for El Niño are predicted to be near 25% during the winter and spring. In summary, ENSO-neutral is favored during the Northern Hemisphere winter 2019-20 (~70% chance), continuing through spring 2020 (60 to 65% chance; click CPC/IRI consensus forecast for the chance of each outcome for each 3-month period).