Storm Forecast
Valid: Fri 16 Oct 2015 06:00 to Sat 17 Oct 2015 06:00 UTC
Issued: Fri 16 Oct 2015 00:20
Forecaster: TASZAREK

A level 1 was issued for S Italy, Albania and W Greece mainly for the excessive precipitation and in lesser extent for the large hail.

A level 1 was issued for Slovenia, Croatia, Bosnia and Herzegovina, Montenegro and parts of Poland, Czech Republic, Slovakia, Austria, Hungary, Italy and Serbia mainly for the severe wind gusts and in lesser extent for tornadoes.

SYNOPSIS

Northern Europe is covered by two blocking high pressure systems over British Isles and W Russia. The main polar jet stream extends from Iceland through N Scandinavia up to N Russia. Large cold drop (cut off) remains almost stationary over S Germany and Alps. On its eastern flank a warm and moist air mass from the C Mediterranean is flowing through W Balkan Peninsula up to Poland. Another cut off approaches Portugal in the end of the forecast period.

DISCUSSION

...S Italy, Albania and W Greece...

Southerly low-level inflow of moist air (mixing ratios ~ 13-14 g/kg) perpendicular to the main flow at 500 hPa, precipitable water exceeding 30mm, the presence of DMC in the CAPE environment up to 2500 J/kg and slow storm motion creates threat for excessive precipitation and thus flash flooding along the coastal areas. Orographic lift and almost stationary convective cells along the Albanian and Greece coast increases the threat of such phenomena. Intense precipitation threat should be the highest in the late afternoon hours while the thunderstorms along the coastal areas should be active during the whole forecast period. It is likely that within the presence of DLS up to 15 m/s convection may organize into multicells capable of producing locally large amounts of marginal hail.

...Slovenia, Croatia, Bosnia and Herzegovina, Montenegro and parts of Poland, Czech Republic, Slovakia, Austria, Hungary, Italy and Serbia...

High-shear low-CAPE environment is expected to occur within the forecast period. On the eastern flank of the cold drop placed over S Germany an impressive mid-level flow with DLS up to 35 m/s and MLS up to 15 m/s overlaps with marginally unstable warm and moist air mass flowing from C Mediterranean. Although thanks to the advection of the potential vorticity there will be the source of the QG-lift, a shallow free convective layer with the low cloud tops and questionable CI may be the limiting factor for the DMC. Nevertheless, in such environment convection may organize into supercellular thunderstorms and/or linearly organized convective system capable of producing severe wind gusts. NWP models simulate that the highest CAPE values up to 200-400 J/kg may be available in E Austria, W Hungary and S Czech Republic, thus in these areas the threat for severe weather phenomena seems will be the highest. Locally enhanced LLS up to 10 m/s cannot also rule out tornado occurrence. CI should take place around noon, thunderstorms are expected to weaken in the evening hours.