CONVECTIVE FORECAST
VALID 06Z TUE 13/04 - 06Z WED 14/04 2004
ISSUED: 12/04 18:27Z
FORECASTER: DAHL

General thunderstorms are forecast across the central Mediterranean regions and SE Europe.

SYNOPSIS

Quasistationary upper low is present over the central Mediterranean. Strong SSWLY flow ... connected to N-European frontal zone ... is present at the SE periphery of the Mediterranean upper low. Weak SFC low pressure area over the central Mediterranean ... is expected to strengthen over the N Balkan States as vort max embedded in the SSWLY flow overspreads the region during the first half of the day. Trailing cold front will accelerate east and extend from W Turkey across the Black Sea into central Romania by Wednesday 06Z.

DISCUSSION

...Central Mediterranean ... SE Europe...
Some of Monday's soundings of the theta-e plume E of the cold front reveal the presence of steep lapse rates associated with an EML originating from the N Sahara ... however ... thermodynamic profiles vary substantially across the region ... especially the mid-level lapse rates and the depth of low-level moisture ... with the lapse rates likely being mixed out locally by convection. Nonetheless ... current TSTM activity ... and local presence of EML/deep low-level moisture suggests that CAPE is present over portions of SE Europe.

Indications are that at least weak CAPE will be present in the pre-frontal environment on Tuesday. Convection will likely initiate/redevelop along the cold front over the Balkan States as DCVA-related UVV's overspread the front. Along the warm front farther N ... elevated TSTMS are expected to continue throughout the period. TSTMS will likely tend to become more high-based over the elevated terrain of the central Balkan States where inverted-V type profiles should be present during the day. Farther S towards Greece ... low-level moisture should generally be somewhat deeper/richer ... and more strongly capped.

Degree of instability is somewhat uncertain ATTM ... GFS does not simulate CAPE over Greece and the Aegean Sea and about 500 J/kg over the central Balkan States. 500 hPa flow is progged to increase towars the south ... with 20 to 30 knots over the central Balkan ... and about 70 knots over the S Ionian Sea ... Greece and the Aegean. The high-based convection will have some potential for producing strong outflow winds ... but relatively weak large-scale forcing/shear over this region should limit allover severe-weather threat. Better chances of severe TSTMS will exist ahead of vort max ... where more benign shear will be present. Models assume weakening of the theta-e tongue during the day ... and CAPE may indeed struggle to develop. However ... if storms form ... linear organization is likely ... posing primarily a threat of severe straight-line winds. Isolated cells ahead of/in the line may attain updraft rotation with an attendant threat for large hail and maybe a brief tornado or two. Strong forcing may offset weakening thermodynamic profiles ... but refraining from SLGT ATTM.

In the polar air beneath the upper thermal low ... a few TSTMS may form over the Mediterranean Sea and Italy ... severe evolution is unlikely owing to weak CAPE/shear.

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