Relative Skill of IFS Models

It is important to have measures of both forecast skill and relative differences in error of ensemble control, ensemble mean, and individual ensemble members.  This allows the forecaster to assess the strength of one product over another and the way this varies through the forecast period.  The Anomaly Correlation Coefficient (ACC) and the Equitable Threat Score (ETS) show the comparative performances on a global scale.   The relative differences in error with lead-time shows comparative errors with lead-time.  Relative weights can be assigned to the ensemble at different lead-times to better use the strengths of each in a more structured way.

HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical and the output is known as ensemble control forecast (ex-HRES).  It might be thought of as a deterministic model yielding deterministic results.  But the unperturbed ensemble control forecast (ex-HRES) is only one of the set of perturbed members in the ensemble.   Each ensemble member and the ensemble control forecast (ex-HRES) is equally probable.  Any individual ensemble control forecast (ex-HRES) may not be the most skilful compared to other ensemble member forecasts, and in isolation it cannot provide an estimate of forecast uncertainty or confidence.

Note: HRES output is maintained for the convenience of users but will be withdrawn in a future update cycle. are scientifically and computationally identical.



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