ENSO Forecast Plumes

This animation of plume diagrams depicts recent forecasts of El Nino and the Southern Oscillation (ENSO) produced by the North American Multi-Model Ensemble (NMME). Embedded histograms are used at each forecast lead time in order to convey information about the variability in the ensemble forecasts in a clear and easy-to-interpret format. This graphic is intended to complement the plume diagrams already in use at CPC and IRI for illustrating ensemble forecasts of ENSO.

Click here to see the archive of individual plume diagrams.

The animation shows the plume diagram for eighteen recent forecasts. The abscissa depicts time in monthly mean increments. The quantity on the ordinate is the NINO3.4 sea surface temperature anomaly index, which is an average of SST anomalies over a region in the central tropical Pacific [(5°S-5°N)(170-120°W)]. The observed value of the NINO3.4 index is displayed with a thick yellow line outlined in black. For each forecast lead time, a left-aligned histogram is displayed. The length of the histogram bars indicates the number of NMME members with a predicted value of NINO3.4 in that 0.25-degree range. The histograms are colorized by value of the index for quick readability, and a thin line along the left edge of each histogram shows the full range of values. The graphic also identifies the mean from each contributing model (color-coded, see key in left corner) and the multi-model ensemble mean (drawn with a thick black dashed line). The total number of members in each model and the NMME is also shown in the key.

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