CONVECTIVE FORECAST
VALID 06Z MON 11/10 - 06Z TUE 12/10 2004
ISSUED: 11/10 01:36Z
FORECASTER: GROENEMEIJER

There is a slight risk of severe thunderstorms forecast across central and southwestern Italy and the central and southern Adriatic Sea and its coastal areas, including parts of Croatia, Serbia and Montenegro and Albania.

There is a slight risk of severe thunderstorms forecast across northwestern Turkey

SYNOPSIS

Monday at 06 UTC... a large blocking high is centered over the North Sea. On its southwestern flank a cold-core low is located over the Bay of Biscay. In the south... a westerly mid/upper flow is present over the Mediterranean.

DISCUSSION

...central Mediterranean ...
An almost stationary frontal zone is expected along a line from northern Algeria to southern Italy to the west-central Black Sea. Almost dry-adiabatic lapse rates have been observed by Sunday's 12Z soundings in Trapani and Brindisi, which in combination with some low level moisture yields between 1000 and 3000 J/kg MLCAPE50, but with considerable convective inhibition. This seems to have inhibited convective initiation within this air mass on Sunday.
North of the frontal zone, lapse rates are less steep, but with abundant low-level moisture up to 2000 J/kg of MLCAPE50 can still be reached as was observed at Roma/Pratica di Mare Sunday at 12Z. Numerical guidance suggests that the front will move slowly southward, putting the Adriatic region and all of Italy but Sicily and Calabria in the weakly-capped air-mass. Scattered storms, including low-topped supercells and small clusters, should be possible here as deep-layer shear is in the 20-30 m/s range. They create a small threat of large hail, strong gusts and possibly a few (likely weak) tornadoes. Models suggest there is potential for a large convective system to develop affecting western mainland-Italy and/or Sicily during the late evening and/or overnight. Such a MCS would bring a risk of hail and severe winds.

...northwestern Turkey...
The aforementioned cold front is expected to move southeastward and reach northwestern Turkey at the end of the afternoon. Storms are expected near the front in an environment of rather strong deep-layer (0-6 km) shear of around 20 m/s and a few 100's of J/kg of CAPE. This may enable a couple of (embedded) supercells to form, posing a threat of large hail, strong winds and perhaps a tornado.

...southwestern France...
On the eastern and southeastern flank of the low-pressure area over the northeastern Bay of Biscay, neutral to slightly latently unstable air is present. Scattered storms are forecast, which -given strong low level winds- may be accompanied by rather strong gusty winds.

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