Department of Forecasting and Warning, SHMI - Slovakia
This presentation is devoted to some remarkable downburst cases in Slovakia and their research on Slovak Hydrometeorological Institute. During the last two years were collected and studied small-scale convective events with signs of strong downdraft and gusty outflowing winds. Some of the selected cases were accompanied by considerable damages (like severe downburst in Nižná Olšava on July 8, 2000). Most of the downbursts were characterized by wet microburst or intermediate microburst type of structure according to the vertical temperature and humidity profile. The macro and mesosynoptic conditions were specified with use of synoptic analysis, satellite imaginary (METEOSAT), NWP products and vertical cross-sections (ARPéGE/ALADIN global and limited area models). To observe the development and behaviour in small scale, the combination of radar and surface measurements was used, sometimes with aid of visual kinds of observation (e.g. photographs) and damage inspection. The final product was a mesoscale reconstruction of the downburst type, it’s range and propagation of the edge of the outflow.
The results of the mentioned case studies lead us to following conclusions:
• because of small scale of the observed phenomena it seems very complicated to register them on the whole territory of Slovakia. It’s not easy to find an unambiguous evidence of downburst impact on distant places from synoptic stations or radars.
• thatwhy should be reasonable to concentrate on areas with good conditions for downburst observations and with high importance of early warnings on such events. These might be above all the areas of airports near the cities Bratislava and Košice.
It’s necessary to increase together the number of surface measurements with quality of radar measurements to provide reliable downburst detection.
• some special, in our country not yet standard types of measurements are required for above mentioned purpose. These are data from automatic stations available every minute with system of early recognition of wind peaks and characteristic features of downburst outflow. In radar detection should be prefered short range measurements on low levels with high quality products (including the resolution and folding limits).
• study of macrosynoptic conditions favourable for severe downdraft occurance in central Europe could be provided with international cooperation (i.e. to make a common database of situations). The existing „tornado" list server (tornado@mail.shmu.sk) is available for basic information exchange.