The CEMS-flood sub-seasonal and seasonal products are essentially the same across the two systems and similarly the same across EFAS and GloFAS. Below we introduce the available products and their main features.
River network
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map
The river network summary map layer shows the combined expected forecast anomaly and uncertainty signal in a simplified way for each forecast lead time (Figure 1). The lead time is weekly (always Monday to Sunday with the weekly average river discharge) in the sub-seasonal and monthly in the seasonal (always calendar month with the monthly average river discharge).
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The forecast signal is shown by colouring of all river pixels above a certain minimum catchment area (currently 50 km2 in EFAS and 250 km2 in GloFAS). Each of these river pixels are coloured by the expected anomaly category and the uncertainty category. There There are altogether 7 anomaly categories (from 'Extreme low' to 'Extreme high') and 3 uncertainty sub-categories (from 'Low to 'High') defined, based on the extremity level of the ensemble forecast members in the 100-value climatological distribution and the mean and standard deviation of these rank values (see Figure 1). The details of the computation methodology is described here: Placeholder CEMS-flood sub-seasonal and seasonal forecast anomaly and uncertainty computation methodology.
In total, there are 15 forecast signal categories coloured on the river network map. Out of the 7*3 possible category combinations, 5*3 are represented by colours, after the middle three anomaly categories ('Bit below', 'Normal' and 'Bit high') are merged into one 'Near normal' category. The choice of 5 anomaly categories for the colouring allows the users to focus on the larger anomalies, supplemented by the 3-level uncertainty representation. The different categories and the related colours are introduced in Figure 1 below.
Figure 1. Example snapshots List of the sub-seasonal and seasonal river network summary maps with the reporting points, animanomaly and uncertainty categories defined with the used colours on the river network map.
On the river network summary map, however, only 5 anomaly categories are displayed, after combining the middle three into one larger 'Near normal' category, which allow the users to focus visually on the larger anomalies. Each of these categories are divided into three sub-categories by the uncertainty, as low, middle and high uncertainty, in total making it into 15 forecast signal categories. The inset figure in both Figure 1a and 1b shows the 15 categories and the corresponding colours on the maps.
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