Valid: Fri 15 May 2020 14:00 to Fri 15 May 2020 17:00 UTC
Issued: Fri 15 May 2020 13:48
Trends are monitored for a possiblity of surface-based convective initiation near the Carpathian mountain range between southern Ukraine and northern Romania.
Satellite imagery reveals deepening of Cu field over the area of interest. Towards south, dense cirrus clouds have limited boundary-layer mixing and inhibited cumulus growth. Surface observations show 2m temperature of around 25 deg C, with dewpoints between 13 and 15 deg C, which is in line with NWP forecasts of 12 - 15 UTC conditions over the region. It can be expected that at least several hundreds J/kg of MLCAPE are now available.
Synoptic-scale lift is forecast to increase over the area in the next couple of hours as the short-wave trough approaches. Subsequent moistening will increase chances of initiation, which is problematic given very strongly sheared environment. Any storm that succeeds in such setup will likely become a supercell with threat of large hail and severe wind gusts.
That said, the area of favourable conditions for intense, surface-based storms is very narrow. East of the Carpathians, surface observations show cooler and drier airmass with 0 J/kg of SBCAPE. Thus, even if storms eventually succeed in initiation, there will be rather brief window for surface-based, supercellular convection. As storms cross the mountains, they will likely become elevated.
Besides this area, more widespread initiation of elevated convection is expected to the north, associated with isentropic lift along the frontal boundary.