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The forecast signal is shown by colouring on the map product layers, either for individual river pixel pixels or larger basin basins (see the further product details below in the subsequent sections). Each of these river pixels or basins are coloured by the expected anomaly category and the uncertainty sub-category defined for the actual forecast. There are altogether 7 anomaly categories (from 'Extreme low' to 'Extreme high') and 3 uncertainty sub-categories (from 'Low to 'High'), based on the extremity level of the 51 ensemble forecast members in the 100-value climatological distribution and the mean and standard deviation of these 51 rank values. The details of the computation methodology is described in: Placeholder CEMS-flood sub-seasonal and seasonal forecast anomaly and uncertainty computation methodology.
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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 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. List of the anomaly 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.
The 15 pre-defined anomaly and uncertainty category combinations are used with the 15 colours, as described in the previous section (see e.g. Figure 1).
Figure 2 shows an example, which Figure 1a highlights some river sections with the explanation of the assigned colours and the corresponding anomaly and uncertainty levels. Each of the 5 anomaly categories have a distinct colour, where the 3 uncertainty categories are indicated by lighter colours as the uncertainty increasesBoth Figure 2a and 2b include the colour legend with the 15 categories and the corresponding colours (same as in Figure 1), for easier interpretation.
The river network summary map also contains the reporting points, which are labelled in Figure 1b2b. These are river locations, where detailed information is provided about the evolution of the forecast signal over the forecast horizon. These reporting points are either either fixed points, which are also used in the medium-range flood products and the basin-representative points, which are selected locations on a one point per basin basis. Further details about the basins and the representative points are available here: Placeholder CEMS-flood sub-seasonal and seasonal basins and representative stations.
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Figure 12. Example snapshots of the sub-seasonal and seasonal river network summary maps with the reporting points, animation lead time navigation and river pixel colours explained.
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