Storm Forecast
Valid: Sat 19 Sep 2015 06:00 to Sun 20 Sep 2015 06:00 UTC
Issued: Fri 18 Sep 2015 20:24
Forecaster: DAFIS
A level 1 was issued for Belarus and parts of Ukraine mainly for excessive rain, large hail, severe wind gusts and tornadoes.
A level 1 was issued for Croatia, Bosnia and Herzegovina, Italy and parts of North Africa mainly for excessive rain, large hail and severe wind gusts.
SYNOPSIS
A longwave trough crosses the continent and shifts eastward, before the formation of an upper air cold pool on Sunday that will travel towards the Mediterranean Sea. A vorticity lobe in mid-levels shifts east to Italy and the West Balkans, over unstable but not so strongly sheared air masses. The strong southwesterly flow in Italy and West Balkans will advect these air masses onshore and convection will be orographically enhanced. Moreover a cyclonic vortex in NE Europe results in frontogenesis in eastern parts of the continent.
DISCUSSION
.... Belarus and NW Ukraine ....
A stationary front is forecast over this area, where warm and moist air masses have been advected from the southwest. Several convergence zones extending from Croatia all the way to Belarus, will result in convective phenomena, while in the level 1 area we forecast the most severe events such as excessive rain due to high PW over the area and the slow motion of the storms. DLS will be in the range of 15-20m/s that is supportive for large hail formation and MLCAPE is about to reach 1200 J/kg. Some severe wind gusts may also occur within the strongest cells as SREH is locally forecast to exceed the 400 mē/sē so the storms will have strong rotation resulting in strong updrafts/downdrafts. Tornadoes are also not ruled out because of the strong LLS and the 0-1km SREH.
.... Croatia, Bosnia and Herzegovina, Italy and North Africa ....
Rather high CAPE is forecast for these areas, especially near the coasts and overlaps with DLS in the range of 15-20 m/s which is supportive for the development of organized thunderstorms. Diurnal heat will be the steering mechanism of the convective phenomena but also a cold front approaching from the NW Mediterranean Sea will fire up some cells. We expect some strong cells in NE Italy and N Africa able of excessive rain and large hail, but the main threat will be at the east coast of the Adriatic Sea where a MCS or two will form late in the afternoon. In the morning of Sunday, waterspouts in the Adriatic Sea are not ruled out due to LLS and rather weak low level wind field.
