For each of several regions of the equatorial tropical Pacific the forecast graphs (called plume diagrams), show the predicted area average of monthly mean sea-surface temperature anomaly for each member of the ensemble forecast (red lines). The observed SST anomaly for the six months preceding the forecast is also shown (black line).
Plume diagrams are provided for regions Niño3 (5° S-5° N, 150° W-90° W), Niño3.4 (5° S-5° N, 170° W- 120° W) and Niño4 (5° S-5° N, 160° E-150° W). These areas are commonly used for monitoring the anomalous warming and cooling in sea-surface temperature in the equatorial tropical Pacific associated with El Niño and La Niña. In particular, Niño3.4 is a commonly used indicator for the likely impact of El Niño and La Niña events on associated widespread global climate variability around the globe.