Estofe.org DISCUSSION Eastern Hungary and Slovakia, western Ukraine and Belarus Associated with the cut-off low, a surface cold front has crossed Poland during the night hours. Morning observations indicate moderate boundary-layer moisture along the frontal boundary with dewpoints around 15°C. This is also indicated by latest soundings that show a mixing ratio around 8 g/kg below 800 hPa combined with steep lapse rates. Above the boundary-layer, rather warm mid-level layers have begun to cool in response to QG forcing due to the approaching cut-off low. The Poprad sounding indicates weak CAPE at mid- levels and thunderstorms have formed ahead of the cold front from eastern Hungary to western Ukraine. Daytime heating is expected to result in CAPE values around 1000 J/kg given the rather deep boundary-layer moisture overlapping with steep low- level lapse rates and rather cold mid-levels. Lift will be present near the cold front that will move slowly east across the Ukraine and Belarus. Thunderstorms are forecast to intensify in the late morning hours spreading into the eastern Ukraine. In the afternoon, activity will spread into Belarus as well. Storm organization will be rather limited given the weak vertical wind shear overlapping with CAPE and forcing. Latest models indicate slightly increasing southerly winds ahead of the cold front at 700 hPa. The result is slightly enhanced low- level vertical wind shear around 10 m/s in the lowest 3 km. Current thinking is that multicells are able to form that move northward along the frontal boundary. The main threat of these storms will be excessive rain due to training storms. Additionally, large hail is not ruled out with the stronger storms, especially when supercells can develop.
Posted on: Thu, 11 Jul 2013 07:44:05 +0000
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