CONVECTIVE FORECAST
VALID 06Z SAT 01/01 - 06Z SUN 02/01 2005
ISSUED: 31/12 19:03Z
FORECASTER: DAHL

General thunderstorms are forecast across the central and eastern portions of the Mediterranean Sea.

SYNOPSIS

Vigorous Atlantic upper trough with associated SFC cold front are expected to cross the British Isles on New Year's Day ... with the SFC cold front stretching from S Scandinavia across central Europe into the Biscay by the end of the period. Upper low over the central Mediterranean is progged to move off to the eastern Mediterranean regions towards the end of the period.

DISCUSSION

...British Isles...
There are no indications that appreciable CAPE will exist in the warm-sector air mass ahead of the cold front expected to cross the UK ... but quite strong large-scale vertical motion ... strong deep-layer and low-level shear and presence of extensive dry slot overhead the SFC cold front (per GFS 12Z) hint at possibility of lines of forced convection along the cold front ... which has shown to produce isolate and brief tornadoes in the past ... as well as severe straight-line winds. Considerable uncertainty currently exists with this sort of strongly forced shallow severe convection ... will thus not issue categorical severe outlook.

...North Sea...
Large field of Benard-type convection will likely exist in deep polar air beneath the Atlantic trough ... which may locally be enhanced ahead of small vort maxima. This convection may produce a few lightning flashes ... but these should be too isolated for a TSTM outlook. Strong wind gusts will likely accompany this activity.

...central Mediterranean...
It appears that majority of convection will occur within relatively barotropic cold-pool region of the Mediterranean upper low ... with quite limited severe TSTM threat given the weak shear in this region ... and nearly neutral lapse rates. However ... vort max is expected to travel across the Aegean Sea late in the day at the E periphery of the main upper low ... which may support a few TSTMS. Deep shear will be somewhat stronger in this regime ... however ... given very weak thermodynamic profiles and weak low-level shear ... organized severe TSTM threat should be limited though especially in the E portions of the TSTM area a few strong wind gusts and small hail could occur.

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