Experimental Seasonal Forecasts

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.

The June experimental predictions produced by SPEAR indicate a high probability of a very strong El Niño by fall. Compared with last month, the uncertainty of the strength due to chaotic weather variability is reduced, as shown by the reduced model spread (the differences between the individual purple lines). This month, all 30 ensemble members (dotted purple lines) have a peak relative Niño-3.4 index above 2 °C next fall or early winter, values that generally are only reached every one to two decades. This level of agreement among ensemble members indicate high confidence in a strong El Niño.

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 June 1, 2026 and extend through May 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.