1Hungarian Meteorological Service, Hungary
2University of Pécs, Hungary
Summer weather can cause severe situations in the Carpathian Basin. Convective events like thunderstorms (sometimes tornado producing supercells), squall lines, occur frequently during the summer ( Horvath and Geresdi, 2001). To solve the very short range forecast of these phenomena, Hungarian Meteorological Service (HMS) run a project to develop a nowcasting system. The system, called "Mesoscale Analysis, Nowcasting and Decision Routines (MEANDER)" consists of two main segments: an analysis and a forecasting subsystems. The analysis system assimilates all available real time data and creates a high resolution 3D objective analysis. The final products of the analysis segment are sounding data at all grid points corrected with available measurement of the synoptic stations. These data are used to initiate a one dimensional cumulus jet model. This model is applied to estimate the maximum vertical velocity, the maximum height of the cloud top and the maximum hail size. These parameters characterize the thunderstorms at given grid points. The second segment of MEANDER is the forecasting part. The forecasting part can be divided into two subsegments: a "linear" forecast (0-3 hours) and a numerical forecast (3-6 hours). During the "linear" forecast the parameters are interpolated from the analysis data and the 3 hour-forecast fields. Beyond the time period of 3 hours forecast time a meso-scale cloud model is applied. In this research case studies were made to investigate the sensitivity of thunderstorm forecast to the applied assimilation technique.