## 4 Concluding Remarks  
Because of the ongoing changing climate, extreme rainfall events' frequency at the global scale is expected to increase, thus resulting in high social and economic impacts. A full Meteo/Hydro/hydraulic forecasting chain combining heterogeneous observational data sources is a key element of a complete Early Warning System; it supports decision makers (e.g., Civil Protection Authorities) to correctly predict these events, monitor them, \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & **Threshold Criticality** & **Benchmark** & **WRF-DA** & **WRF-OL Prob.** \\ \hline
**Basin** & **Section** & **Qpeak** & **Qpeak** & **Qpeak** & **QpeakMin** & **QpeakMax** \\  & & **[m\({}^{\prime}\)/s]** & **[m\({}^{\prime}\)/s]** & **[m\({}^{\prime}\)/s]** & **[m\({}^{\prime}\)/s]** & **[m\({}^{\prime}\)/s]** \\ \hline Lentini & Lentini & 403 & 767 & 532 & 968 & 1100 \\ Anapo & Sracusa & 467 & 85 & 507 & 297 & 331 \\ Simeto & Reitano & 1742 & 1492 & 4093 & 5200 & 5600 \\ Alcantara & Chianchitti & 942 & 1340 & 1467 & 1049 & 1446 \\ Catona & Reggio Calabria & 83 & 98 & 137 & 54 & 97 \\ Amendola & Calimara & 330 & 267 & 706 & 294 & 401 \\ Petrace & Rizziconi & 756 & 620 & 709 & 428 & 556 \\ Bonamico & Casignana & 349 & 258 & 756 & 353 & 542 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison between forecasts and benchmark peak flows. Threshold – criticality is a value of flow for which criticality as flooding or other ground effects happen; the benchmark is the run on observation peak flow; WRF-DA is the forecast chain fed with WRF model that assimilates both radar and ground temperature data; WRF-OL is the forecast chain without assimilation. Figure 16: Comparison between forecast flooded area **(left panel)** using WRF-DA forecast run of 24 October at 00 UTC and flooded area using ground data as input for Flood-PROOPS **(right panel)**. and evaluate their effects and damages, speeding up the response and recovery. In this context, the CIMA Foundation, using the cloud-resolving WRF without (WRF-OL) and with the in situ weather stations' data assimilation (WRF-3 DVAR), the fully distributed hydrological model Continuum within Flood-PROOFS, the automatic system for water detection (AUTOWADE), and the hydraulic model TELEMAC-2D, operated in real time (or near real time) to predict the weather evolution and the corresponding hydrological and hydraulic impacts of the Apollo Medicare between 24 and 26 October 2021 over the Sicily and Calabria regions. The WRF-OL simulation (available at 00 UTC, 24 October 2021) showed a very good predictive capability concerning the timing and the location of most intense rainfall phenomena over Catania and Siracusa provinces in Sicily, thus also enabling very accurate discharge peaks and timing predictions for the creeks' hydrological network peculiar of eastern Sicily. Based on the WRF-OL model predictions, the daily run of the AUTOWADE tool, using Sentinel-1 (S1) data, was anticipated with respect to the schedule to quickly produce a flood map (S1 acquisition performed on 25 October 2021, at 05 UTC, flood map produced on the same day at 13 UTC). Moreover, considering that no S1 images of eastern Sicily were available during the period of 26-30 October, 2021, an ad hoc tasking of the COSMO-SkyMed satellite constellation was performed to overcome the S1 data latency. The resulting automated operational mapping of floods and inland waters was integrated with the Floodwater Depth Estimation Tool, FwDET, forecast to obtain water depth maps from satellite observations. Subsequently, the execution hydraulic model TELEMAC-2D starting from the Flood-PROOFS peak discharge forecast on observations allowed to obtain both water depth and water velocity evolution in time and space. The water depth results obtained with the two different tools were combined to overcame the intrinsic limits of the single approaches to obtain a more complete water depth map in near real time to highlight the most affected areas and estimate damages.