This plume diagram depicts 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.
Select a year from the menu below, then hover over the months to see each image in the archive.
Additional resources include an animation of forecast plumes spanning the recent El Nino event, the most recent plume diagram, and the GrADS script used to create these plumes. No data download required!
The abscissa depicts time in monthly mean increments, beginning two months before the forecast initialization date and extending seven months into the forecast. 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. At 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.
Please send comments or questions to Jennifer Adams:
(jadams21 at gmu dot edu)