Storm Forecast
Valid: Tue 16 Feb 2016 06:00 to Wed 17 Feb 2016 06:00 UTC
Issued: Mon 15 Feb 2016 21:45
Forecaster: DAFIS

A level 1 was issued for Italy, Croatia, Slovenia, Bosnia and Herzegovina mainly for excessive rainfall, severe wind gusts, large hail and tornadoes.

SYNOPSIS

The advections of very cold air masses with high PV values over West Mediterranean Sea have resulted in cyclogenesis on the surface. The jet stream is found way to South, over North Africa and a cyclonic vortex is found over Sardinia and Corsica. Furthermore, a high pressure system prevails over central Europe and a fast moving cyclonic vortex is stepping east, towards Russia during Tuesday. Balkan states and East Mediterranean experience an intense low tropospheric WAA with a strong load of dust. Apart from the coasts of the Mediterranean Sea, we do not expect convective phenomena elsewhere (extremely low coverage of convection may be found in NW Ukraine and SW Russia, out of our domain and lower than 15%).

DISCUSSION

Cold air masses over the mild and moist Mediterranean Sea lead to quite steep lapse rates and the formation of CAPE. During the first half of Tuesday, the convective activity will take place mostly over and near Sardinia and the West coast of Italy, where NWP models predict MLCAPE up to 800 J/kg overlapping with strong DLS with values that exceed 25 m/s. Also convection will take place in the occlusion regime, enhanced by orography, with persistent convective rainfall being the main threat. Moreover, CI in Adriatic Sea should begin before 12z and one or two clusters of thunderstorms are forecast to move on shore, in Croatia. Strong DLS and veering winds on the vertical axis, will result in high values of SREH0-3km, in excess of 500 m²/s², while the S-SW flow near the surface will advect moist air masses (mixing ratio 9-11 g/kg) on shore. These progressively unstable air masses and the strongly sheared environment, indicate that every severe event is possible to occur, including tornadoes among the large hail, excessive rainfall and severe wind gusts. Strong 0-3 km Bulk shear and high SREH0-1km overlap with SBCAPE near the coasts of Croatia, where waterspouts or tornadoes are forecast. A level 2 was considered for this area but a level 1 was issued due to low coverage of the convection, apart from non-convective phenomena.