September initialization · ECMWF SEAS5 calibrated with CHIRPS · ONDJ R3 (Deyr) rainfall domain
ONDJ 2026/27 rainfall outlook
Research reconstruction · not an official EMI or ICPAC forecastTarget period ongoing (ends 31 Jan 2027)
The forecast leans toward above normal rainfall in the ONDJ R3 (Deyr) rainfall domain: averaged over the area, the local probability of above normal is 58%, against about 33% for climatology. Mean forecast rainfall is 265 mm against a 1993/94–2024/25 average of 188 mm (+77 mm, +41%).
Average local probability
Each grid cell has its own tercile probabilities; these are their averages over the 100% of the area that has probabilities. They are not the probability that the area-total rainfall falls in a category.
Rainfall amount
Amounts cover 100% of the area. They come from the amount-corrected ensemble, calibrated separately from the probabilities, so the two can differ slightly.
Forecast signal
Strong tilt toward above normal
Largest area-average probability 58%, compared with a one-third reference. The local climatological probabilities (observed tercile frequencies in the training years) are close to, but not exactly, one-third. Based on probabilities only.
Historical skill — ONDJ R3 (Deyr) rainfall domain
Moderate improvement over climatology (interval above zero)
Probability skill (RPSS) +0.133 for ONDJ, cross-validated 1993–2016 (95% interval +0.032 to +0.245); better than climatology in 18 of 24 years. One-target p = 0.010; adjusted for testing 5 targets (Holm), p = 0.040 (still significant). Details
Signal strength describes how far this forecast's probabilities depart from climatology. Historical skill describes how forecasts made the same way scored in past years. A strong signal is not a confidence rating.
All targets in this cycle
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ONDJ 2026/27
B 16% · N 26% · A 58%
Target period ongoing (ends 31 Jan 2027)
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Oct 2026
B 26% · N 31% · A 42%
Target period ongoing (ends 31 Oct 2026)
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Nov 2026
B 20% · N 25% · A 54%
Target period starts 1 Nov 2026
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Dec 2026
B 36% · N 26% · A 38%
Target period starts 1 Dec 2026
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Jan 2027
B 32% · N 33% · A 36%
Target period starts 1 Jan 2027
The targets as a table
| Target | Period | Below / near / above | Probability coverage | Anomaly | Verification status |
|---|---|---|---|---|---|
| ONDJ 2026/27 | 1 Oct 2026 – 31 Jan 2027 | 16% / 26% / 58% | 100% of area | +77 mm | Target period ongoing (ends 31 Jan 2027) |
| Oct 2026 | 1 Oct 2026 – 31 Oct 2026 | 26% / 31% / 42% | 100% of area | +24 mm | Target period ongoing (ends 31 Oct 2026) |
| Nov 2026 | 1 Nov 2026 – 30 Nov 2026 | 20% / 25% / 54% | 100% of area | +40 mm | Target period starts 1 Nov 2026 |
| Dec 2026 | 1 Dec 2026 – 31 Dec 2026 | 36% / 26% / 38% | 100% of area | +5 mm | Target period starts 1 Dec 2026 |
| Jan 2027 | 1 Jan 2027 – 31 Jan 2027 | 32% / 33% / 36% | 62% of area | +2 mm | Target period starts 1 Jan 2027 |
Probability coverage is the share of the area with tercile probabilities; averages are over that share only. Cells with very little reference-period rainfall have no terciles.
Maps
How to read this map
Grey, white and blank areas; smoothing and resolution
Light grey: outside the selected area. Dark grey: inside the area but without values, for example cells where reference-period rainfall is too small for tercile categories, or (percent maps) below 10 mm. White on tercile maps: no category reaches 40%, or two categories tie. Sea cells have no CHIRPS data.
Smoothing and resolution. Maps are drawn on a 12× finer display grid with light Gaussian smoothing (σ = 0.6 grid cells); all numbers on this page use the original 0.25° grid. The model's own resolution is about 1°: each model cell covers 4×4 grid cells, so detail within a 1° box comes from local CHIRPS rainfall statistics used in the amount correction, not from the model.