1National Institute of Meteorology and Hydrology - Romania
2National Institute of Meteorology, STAP - Spain
Romania is vulnerable to severe weather phenomena, which may occur across its territory, due to its climate, geographical position and complex orography. Thunderstorms including hail, high winds or heavy rainfall produce damages and even life losses.
In this study we have investigated weather situations that have driven to severe weather events in the Southern part of Romania were two Doppler radar systems have been installed recently.
The specific configuration of the Carpathians mountains characterized by the strong curvature induces certain airflow in the lower layers of the atmosphere so that the forcing factors guided by the orography imprint similar patterns. Some favorite places for convergence lines in specific synoptic configuration were identified in the Romanian Plain. In the summer months the diurnal heating can produce thermal lows, which are another characteristic mesoscale feature in Romanian Plain, providing the low-level wind share. Local pressure lows can be caused due to the mountain barrier across the general flow (dipolar structure). Severe convective storms can appear in the plains but more often they occur on the southern slopes of the Meridional Charpatians where linear convective systems are formed. The propagation of such systems takes place along the mountain barrier, backward or forward, according to the orientation of the moist low-level jet, until is intersecting a pre-formed convergence line; the new propagation of the squall line becomes along that one. Several cases have been studied in order to catalogue them with respect to the identified conceptual model and it was found that there is a strong connection between the mesoscale orographical forcing and the climatology of these severe convective storms.
In our study, several types of data have been used, among them being radar data, satellite imagery and NWP products. The most valuable information was given by the two Doppler radar systems DWSR - 2500C.
The high resolution limited-area numerical weather prediction model ALADIN was also used for a better understanding of the atmospheric phenomena.