engleski

Heavy rainfall and flash flood in Dubrovnik on 22 nd November 2010

A case with the extreme precipitation in the morning on 22nd November 2010 in Dubrovnik, Croatia, is used as a testbed for the numerical weather prediction model ALADIN. The synoptic situation was characterized by a huge low moving over the Alps with the frontal system covering most of Central Europe and Mid-Mediterranean. During the passage of the cold front over the southern Italy and Adriatic Sea, a secondary cyclone developed and a meso-scale convective system grew within. The rain-gauge measurements exceeded 100 mm/24hr in the area and the one in Dubrovnik measured 161.4 mm/24hr, with a peak intensity of 71.5 mm/h. This was the measured maximum ever measured in Dubrovnik. Different options for initial and boundary conditions will be tested for the 8 km resolution run. In DHMZ, two options are operationally available, from ARPEGE run at Meteo France and IFS model run operationally in ECMWF. A possibility of improving the initial and lateral boundary conditions via the data assimilation is investigated. The ALADIN 8 km model results forecast 24 hour accumulated rainfall from 20 to 100 mm in the area around Dubrovnik, but the maxima over 100 mm are above the surrounding areas of Montenegro and Bosnia and Hercegovina. Experiments using high-resolution (2 km) non-hydrostatic ALADIN model show strong dependency on the model, input data from initial and lateral boundaries. The position and time of the precipitation maxima is very similar to the lower resolution (8 km) run used for initial and lateral boundary conditions. One configuration forecasts precipitation exceeding 100 mm/ 24hr for Dubrovnik.

severe rain; flash flood; convection

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