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Colouring on the charts is implies >90% significance for the anomaly from SUBS-M-Climate. White shading on the maps only implies <90% significance of the anomaly and show where the ensemble forecast is not significantly different from the sub-seasonal range climatology (SUBS-M-Climate), according to a Wilcoxon-Mann-Whitney (WMW) test. It does not necessarily point to a forecast of average nor to a 'don't know' forecast of climatology.
Further information can be gained by inspection of the sub-seasonal anomaly meteogram. Click the mouse over any location on the ensemble charts to produce probability information in meteogram form.
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The sub-seasonal range products should always be used with historical skill metrics in mind.
Broad indications of ensemble performance and predictability in the sub-seasonal range should be taken into account when considering the sub-seasonal range output. Users should consult verification information:
- monthly forecast reliability diagrams (for 2m temperature, surface temperature, total precipitation, mean sea level pressure)
- monthly forecast relative operating characteristics (ROC) diagrams (for 2m temperature, surface temperature, total precipitation, mean sea level pressure).
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- ROC value 1.0 implies consistent Hit Rate and no False Alarms.
- ROC value 0.5 implies no skill with as many Hits as False Alarms.
- ROC value 0.0 implies consistent False Alarm rate and no Hits.
Reliability diagrams
The Reliability diagrams give a measure of the tendency of the forecast system to over- or under-forecast and event. The diagram plots the frequency of a forecast probability of an event against the frequency that the event occurs. Ideally these should match and is shown by the diagonal line. Where the plot lies:
- below the diagonal implies over-forecasting. The forecast probability is greater than the observed frequency.
- above the diagonal implies under-forecasting. The forecast probability is less than the observed frequency.
An explanation of reliability diagrams and ROC diagrams is given in the annex to this guide.
ROCmap - map of Relative Operating Characteristics (ROC)
The ROCmap shows the ROC score computed over each grid point with a resolution of 2.5 degrees longitude by 2.5 degrees latitude. The charts are anomalies derived from previous sub-seasonal range ensemble forecasts compared with SUBS-M-Climate.
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