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The headline forecast skill score is the maximum lead time (in days), up to 30-days ahead, in which the Continuous Ranked Probability Skill Score (CRPSS) is greater than a value of 0.5, when compared to a persistence or climatology benchmark forecast using GloFAS-ERA5 historical river discharge reanalysis (also known as Forced simulation (sfo) within CEMS) as proxy observations (Harrigan et al., 2020b). Forecast skill is calculated using river discharge reforecasts for a set of past dates, based on a configuration as close as possible to the operational setting. ECMWF-ENS medium and extended range reforecasts are used and are run twice per week for the past 20-years with 11 ensemble members.
Scores are shown on the GloFAS map viewer in the 'Forecast skill' layer under the 'Evaluation' menu (an example of the layer is shown here: GloFAS forecast skill product). For each GloFAS web reporting point, the maximum lead time the CRPSS is greater than 0.5 is given, with stations with purple circles having high skill for at longer lead times. The category "0", marked as light pink circles pink circles represents stations that have forecast skill lower than the 0.5 threshold for any lead time. Note: This does not mean that a station has no skill. Only when the CRPSS ≤ CRPSS ≤ 0 is when the forecast has no skill , when compared to a persistence or climatology benchmark forecast.
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