CONVECTIVE FORECAST
VALID 06Z FRI 24/09 - 06Z SAT 25/09 2004
ISSUED: 23/09 14:40Z
FORECASTER: GATZEN

There is a slight risk of severe thunderstorms forecast across eastern Mediterranean

General thunderstorms are forecast across central and eastern Mediterranean, southern Balkans and Black Sea region, Baltic Sea region and western Poland

SYNOPSIS

European upper trough amplifies into central Mediterranean. Cold airmass enters the western and central Mediterranean north of a cold front that is expected from southern France to northern Italy and further to northwestern Black Sea by Friday morning. To the south ... warm airmass is present over the Mediterranean and southeastern Europe. On Friday ... lee cyclogenesis over Italy is expected ... leading to WAA over the Balkans and Black Sea region.

DISCUSSION

...Eastern Mediterranean ...
Warm airmass is present over the Mediterranean ... and latest ascends show steep lapse rates above the boundary layer. Increasing boundary layer moisture as indicated by GFS forecast should lead to sufficient instability to the east of southern Italy, and CAPE of more than 700 J/kg is forecast. During the day ... a short-wave trough is expected to move eastward. In the range of this trough ... a southerly jet streak is expected over the eastern Mediterranean, leading to increasing deep layer wind shear east of the Aegean Sea. In the range of the upper trough ... some DCVA is expected ... and should help to break the weak developed capping inversion. Sowers and thunderstorms are forecast that should move northeastward. Due to increasing vertical wind shear and synoptic forcing east of developing surface low over the central Mediterranean ... strong thunderstorms are possible especially over the eastern parts of the affected region. Multicells and supercells are forecast capable of producing isolated large hail, severe wind gusts and a tornado or two. Best chances for severe thunderstorms are expected in the region of Crete. Convective activity should go on during the night hours and expand northeastward.

...Central Mediterranean ...
As the upper trough expands into the Mediterranean ... lee cyclogenesis is expected over Italy ... leading to easterly surface winds over northern Italy and some WAA along the stalling frontal boundary. However ... poor instability is expected north of the frontal boundary and showers/thunderstorms should be weak. Isolated mesocyclones may be capable of producing large hail and a brief tornado, overall threat seems to be too low to warrant a risk category though. To the south of the frontal boundary/surface low ... DCVA and upper cooling is expected ... and CAPE should reach more than 500 J/kg. Weak vertical wind shear will not support organized convection.

#