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Next in the popup window is the hydrograph, which graphically summarises the climatological, antecedent and forecast conditions (see Figure 4).
The left half of the plot, left of the horizontal dotted line which indicates indicating the forecast start date, shows the past always with 6 lead time periods included (either weeks in sub-seasonal or months in seasonal as in Figure 4a). The is the antecedent condition section. This part includes black dots (connected by black line) indicate , which shows the average weekly (sub-seasonal) or monthly (seasonal) discharge from the so-called water balance, the proxi observations, which are produced as a LISFLOOD simulation forced with either gridded meteorological observations in EFAS, or ERA5 meteorological reanalysis fields in GloFAS. These black dots show This represents the simulated reality of the river discharge conditions, as close as the simulations can go at the actual conditions over the forecast periods (average river discharge over months in seasonal and calendar weeks in sub-seasonal). These it can go to reality in EFAS and GloFAS. It always includes 6 lead time periods of the past on the hydrographs, either the 6 calendar weeks before the first week of the forecast in the sub-seasonal, or 6 calendar months before the first month of the forecast in the seasonal (as in Figure 4a). The black dots are added to the hydrographs retrospectively, after each week (in sub-seasonal) or month (in seasonal) passes and the weekly or monthly mean proxi-observed river discharge values become available. . For the seasonal forecast hydrograph, the water balance is known for all 6 past months at the time of the forecast hydrographs are prodced, run, The users are encouraged to go back and check previous forecasts to see how well the earlier forecasts predicted the anomalies.
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The coloured background is the model climatology (see Figure 4b). This climatology is generated using reforecasts over a 20-year period. Further information on the climatologies and their generation is given on: Placeholder CEMS-flood sub-seasonal and seasonal forecast signal generation methodology. In the
The past past half of the hydrograph (left from the forecast run date vertical dotted line) includes 6 lead time period, either the 6 calendar weeks before the first week of the forecast in the sub-seasonal, or 6 calendar months period before the first month of the forecast.
climatology the climatology is always from lead time 1, so first week (always as days 1-7) or first month (whichever month of the year it is), as that is the closest equivalent to the proxi-observation-based climatology. While While in the forecast half, for each forecast period the equivalent climatology is plotted with that specific lead time. From the climatology, the 5 anomaly categories are coloured, below the 10th the 'Extreme low' with red, above the 90th percentile the 'Extreme high' with blue, the 10th to 25th percentiles zone as 'Low' with orange, the 75th to 90th percentiles as 'High' with cyan and finally the remaining 25th to 75th percentile as 'Near normal' with grey. This 'Near normal' category is the extended one by merging the original 25-40, 40-60 and 60-75 percentile categories, including the narrower 'Near normal', the 'Bit low' and 'Bit high' categories.
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