Posted on September 8th, 2026 in Seasonal Forecasts
The September experimental predictions (purple lines) produced by SPEAR indicate a slightly weaker peak El Niño strength compared with last month’s forecast (green lines), but the current forecast still provides high confidence in a historically strong El Niño later this fall and early winter. Even with this slight decline in peak strength, all 30 ensemble members (dotted purple lines) show that this El Niño will compete with, if not surpass, the strongest events in the historical record. The spread of the 30 ensemble members increases by the spring, indicating that forecast uncertainty increases during the time of year when El Niño often transitions to ENSO-neutral conditions. In contrast with the currently very warm equatorial Pacific conditions, most ensemble members predict below-average temperatures next summer.
The figure shows the latest experimental seasonal predictions of the El Niño-Southern Oscillation (ENSO) from the GFDL SPEAR prediction system. The predictions (purple lines) started on September 1, 2026 and extend through August 31, 2027 (x-axis). The y-axis indicates the strength of El Niño or La Niña, with more positive values indicating a stronger El Niño (warmer water in the east-central tropical Pacific relative to the tropical average temperature). The individual lines represent different forecast realizations starting from slightly different initial states, representing the forecast uncertainty from chaotic climate variability. The thick solid lines represent the average of all realizations, showing the forecast signal after filtering out the influence of chaotic climate variability. The green lines represent the predictions from the previous month, illustrating how much the forecast has changed.
For a comparison with other experimental ENSO predictions from the North American Multi-Model Ensemble (NMME), click here, and for latest NOAA ENSO Outlook, click here. Additional information on ENSO, including impacts, can be found here.