Every forecast cycle is scored against ECMWF ERA5 reanalysis. We publish these metrics transparently so you can assess quality before you buy.
All verification scores are computed against ECMWF ERA5 reanalysis at 0.25° resolution. ERA5 is the closest approximation to ground truth available globally — it assimilates millions of observations from weather stations, satellites, radiosondes, and aircraft into a physically consistent atmospheric state every hour.
For each forecast cycle, we interpolate our predictions to ERA5 grid points and compute standard meteorological scores: Root Mean Square Error (RMSE) for continuous variables, Anomaly Correlation Coefficient (ACC) for pattern verification, and Brier Skill Score (BSS) for probabilistic predictions of binary events (e.g., precipitation exceeding a threshold).
Scores are computed separately for the Northern Hemisphere extratropics (20°N-90°N), tropics (20°S-20°N), and Southern Hemisphere (90°S-20°S). The headline numbers shown on this page are NH extratropical scores, which is the standard benchmark region for numerical weather prediction.
All verification data is available for download via the API. See documentation for the verification endpoint.