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.

River network summary map

The river network summary map layer shows the combined 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 (always calendar month, with the monthly average river discharge).

The forecasts can be advanced (or even animated if needed) with the lead time controller (see Figure 1a bottom left corner) and the users can check the individual signal for each lead time, which currently is 5 or 6 weeks for the sub-seasonal (depending on which day of the week the run date is) and always 7 months for the seasonal.

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 dominant anomaly category and by the uncertainty category.

There are 7 anomaly categories and three uncertainty categories defined based on the extremity level of the ensemble forecast members in the 99-value percentile climatological distribution. The details of the computation methodology is described here: Placeholder CEMS-flood sub-seasonal and seasonal forecast anomaly and uncertainty computation methodology.

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.

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 is indicated by lighter colours as the uncertainty increases.

The river network summary map also contains the reporting points, which are labelled as example in Figure 1b. These are river locations, where detailed information is provided about the evolution of the forecast signal over the forecast horizon. There reporting points are 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.

Figure 1. Example snapshots of the sub-seasonal and seasonal river network summary maps with the reporting points, animation and river pixel colours explained.

Reporting point pop-up window

At the predefined reporting point locations (either fixed or basin-representative) further detailed information is provided about the evolution of the forecast signal.

The first table in the popup window (Figure 2) provides metadata information of the station, the name (if available), country, river, provided coordinates and upstream area and also the LISFLOOD coordinates and upstream area. The provided coordinates and upstream area are from the users as those represent the real river gauge location. These are available only for the fixed points (sometimes provided upstream area is missing). For the basin-representative points, however, only the LISFLOOD coordinates and upstream area are available, as these points were defined solely on the simulated LISFLOOD river network.

The fixed reporting points have a Point ID in the metadata table, which starts with 'SI', while the basin-representative points starts with 'SR'. 

Next in the popup window is the hydrograph, which graphically summarises the climatological, antecedent and forecast conditions.

Figure 2. Example snapshot of the reporting point pop-up window product (for a seasonal forecast).