Extreme rainfall of short duration at local scale: case study of Shkodra

Abstract: Local storms can often generate extreme rainfall of short duration that causes immediate and serious flooding in the local scale. The genesis and rapid development of such storms are a result of complex processes that occur in the dynamics of the storm. In this study are examined the Automatic Weather Station's rainfall data and reanalyses from NWP fields for Shkodra city to search the causes of such extreme rainfall in such a short time. The extreme precipitation generally is created as a result of high vertical instability of a air mass very rich in moisture. While the extreme rainfall of short duration at local scale is mainly related to the convective cells and local thermodynamic factors like the vertical profile of temperature and humidity, depending to the local atmospheric circulation. A retrospective analyses regarding the extreme rainfall of short duration at the local scale may provide a detailed picture of the extreme rainfall behaviour occuring in that area for short time intervals of 1, 3 , 6 up to 24 hours. The analyses of the events of short duration extreme rainfall at a local scale for a long term period may provide good results regarding the estimation of the future risk of the sudden local scale floods for the urban areas. Pairing the incidence of local flash floods with the triggers of these events can serve as an additional tool in forecasting local storms that produce short-term extreme rainfall and flash flooding. This study shows that the increased frequency of events with extreme rainfall and the increasing of the rainfall quantities for short time duration intervals is likely to become a prominent feature of the local storms that bring flash floods in the populated and urbanised areas.

Keywords: Extreme rainfall, local flood, vertical profile, convective rainfall