ENSO Forecasts
Forward-looking ENSO guidance: the Niño-3.4 seasonal outlook from the Copernicus (C3S) multi-model seasonal ensemble, shown as the Niño-3.4 and relative Niño-3.4 anomalies, each monthly and as the 3-month running mean (the ONI and RONI). The atmospheric Southern Oscillation Index forecast now lives on the Atmospheric Response page.
C3S Multi-Model Seasonal Forecast — Niño-3.4 & RONI
ENSO outlook from the Copernicus Climate Change Service (C3S) multi-system seasonal ensemble, initialized the same month at seven centres: ECMWF (SEAS5), the UK Met Office (GloSea6), Météo-France, DWD (GCFS2), NCEP (CFSv2), ECCC (CanSIPS) and the Australian Bureau of Meteorology (ACCESS-S2). The four panels show the Niño-3.4 SST anomaly (top) and the relative Niño-3.4 anomaly (bottom; the CPC/ECMWF index, Niño-3.4 minus the 20°S–20°N tropical-mean anomaly, rescaled per calendar month so it keeps ONI's °C thresholds), each as the raw monthly value (left) and the 3-month running mean (right, which are the ONI and RONI). The relative index removes the background tropical warming that inflates the traditional one. The shaded plume is the spread across all members of all models (full range, 10–90% and 25–75%); each coloured line is one model's ensemble mean; the bold black line is the multi-model mean. Every model is anomalized against its own 1993–2016 hindcast, removing its drift and bias. The Niño-3.4 box is sampled at 1° and the tropical mean at 5°. Dotted lines mark the ±0.5/1.0/1.5 °C thresholds.
