Experimental Seasonal ENSO 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.

The August experimental predictions produced by SPEAR provide high confidence that the current El Niño will continue intensifying through the fall, likely peaking sometime between October and January. Like last month, all 30 ensemble members (dotted purple lines) produce a peak El Niño strength that will compete with the strongest events in the historical record. The narrow spread of the 30 ensemble members and the consistency of this month’s forecast (purple lines) with last month’s forecast (green lines) reflect high confidence and relatively low uncertainty in how this event will unfold over the next 6 months.

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 August 1, 2026 and extend through July 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.

The July experimental predictions produced by SPEAR indicate continued intensification of a very strong El Niño through the fall, peaking by late fall or early winter. All 30 ensemble members (dotted purple lines) produce a peak El Niño strength that is at least competitive with the strongest events over the past century, suggesting that a historically strong event is underway. The forecast this month (purple lines) is notably warmer than last month’s forecast (green lines) over the next six months. The forecast indicates that El Niño is likely to weaken through the winter and into the spring.

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 July 1, 2026 and extend through June 30, 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.