## 3 Results
### A Case Study: 12 November 2019  
The purpose of this section is to point out the impact of LDA on the 3 h precipitation forecast over the sea for a specific case. The event occurred on 12 November 2019, and we focus on the 3 h precipitation between 00 and 03 UTC. For the scope of this case study, the WRF model native grid is considered, with a horizontal grid spacing of 3 km, and no remapping on the IMERG grid is performed. In this time period, precipitation is located mainly on the southern part of the Apulia region (around 17.5\({}^{\circ}\) E-40.35\({}^{\circ}\) N), especially on the Salentine Peninsula, as recorded by rain gauges managed by DPC (Figure 7a). The precipitation intensity is moderate, reaching maxima of 30 mm/3 h. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Elba**} & \multicolumn{2}{c}{**Giglio**} & \multicolumn{2}{c}{**Lipari**} & \multicolumn{2}{c}{**Montecristo**} & \multicolumn{2}{c}{**Pantelleria**} & \multicolumn{2}{c}{**Ponza**} \\ \hline  & C & L & C & L & C & L & C & L & C & L & C & L \\ \hline RMSE (mm) & 7.09 & 5.28 & 13.33 & 11.64 & 6.19 & 4.65 & 8.20 & 8.19 & 4.45 & 3.78 & 9.93 & 11.61 \\ \hline r & 0.71 & 0.85 & 0.50 & 0.60 & 0.85 & 0.92 & 0.48 & 0.48 & 0.81 & 0.91 & 0.62 & 0.58 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: RMSE and Pearson correlation coefficients for six islands in the Central Mediterranean basin around Italy. The statistics are computed considering the daily rainfall forecasts. The daily rainfall forecast is the summation of the eight 3 h forecasts within a day. Figure 7: Precipitation between 00 and 03 UTC on 12 November. (**a**) Precipitation observed by the Italian rain gauge network, (**b**) precipitation estimation by GPM-IMERG Final Run, (**c**) precipitation simulated by the CTRL run, and (**d**) precipitation simulated by the LIGHT run. GPM-IMERG precipitation (Figure 7b) is intense in some regions, in particular over the Ionian Sea. Moderate to intense precipitation is observed over the Adriatic Sea, and the IMERG estimation is in good agreement with rain gauge records on the Adriatic coast. As noted in Section 3.1, when discussing the Taylor diagram (Figure 5), the rainfall of IMERG shows an important change from sea to land, with smaller values over land (due to calibration). This precipitation gradient is sometimes observed in the IMERG dataset for the period considered in this paper and suggests that the rainfall over the central Mediterranean Sea can be overestimated by IMERG. The CTRL run (Figure 7c) simulates an intense precipitation over eastern Calabria region (about 16.5-17\({}^{\circ}\) E and 38-40\({}^{\circ}\) N) and on the central part of the Apulia region, north of Salento. This intense precipitation over Calabria is not observed by rain gauges and satellites. Furthermore, the CTRL run gives an intense precipitation forecast over land, while the IMERG dataset shows a heavy precipitation over the Ionian Sea. Overall, for this 3 h time period, the CTRL run simulates the precipitation pattern to the west of the observed rainfall. Results for the LIGHT run (Figure 7d) show a significant improvement in the precipitation forecast: the precipitation pattern over Calabria is shifted eastward, over the Ionian Sea. This precipitation shift reduces the rainfall amount over Calabria, in better agreement with both rain gauge and satellite observations, and increases the precipitation over the Ionian Sea, in better agreement with the IMERG dataset (although IMERG precipitation is likely overestimated). Both CTRL and LIGHT runs give a reasonable representation of the precipitation maximum between northern Sardinia and the Italian peninsula (about 11\({}^{\circ}\) E-41.5\({}^{\circ}\) N). It is interesting to note that the LIGHT forecast shows a second maximum over the Tyrrhenian Sea, at about 14.5\({}^{\circ}\) E and 39.5\({}^{\circ}\) N, which is not forecast by the CTRL run. This maximum is evident in the IMERG precipitation.