CONVECTIVE FORECAST
VALID 06Z WED 22/09 - 06Z THU 23/09 2004
ISSUED: 21/09 17:57Z
FORECASTER: DAHL

There is a slight risk of severe thunderstorms forecast across W Black Sea and the central Ukraine.

General thunderstorms are forecast across the SW Iberian Peninsula.

General thunderstorms are forecast across N ... NE ... and N-central Europe.

SYNOPSIS

Large-scale upper low over the N Baltic Sea/central Scandinavia is progged to remain in place ... exhibiting rather narrow band of quite vigorous mid/upper flow at its western ... southern and eastern periphery. Intense imbedded vort max is coherently progged to reach the N British Isles towards Thursday morning. At low levels ... the NRN half of Europe is covered by extensive quasi-stationary SFC low pressure system centered over central Scandinavia ... with the main cold front expected to curve from NW Russia across the NW Black Sea into the central Mediterranean by Wednesday 12Z.

DISCUSSION

...central Europe...
Mainly diurnally driven convection will likely form again in deep polar air over N-central ... N and NE Europe. It looks that bulk of the convection will occur just to the N of fairly strong mid/upper jet (40+ m/s at 500 hPa and 60+ m/s at 300 hPa). However ... weak perturbations ... and gradual eastward shift of the WNWLY jet should promote some DCVA ... which could support relatively deep convection close enough to the upper jet to yield strong kinematic storm environment. If so ... short/bowing lines may briefly develop as well as shallow mesocyclones ... supporting quite isolated marginally-severe hail and wind threats. Also ... a brief/weak tornado or two cannot be excluded. However ... Majority of the storms should be non-severe and a SLGT is not necessary ATTM.

...W Black Sea ... central Ukraine...
It appears that an elevated mixed layer generated over Turkey will be advected northwards ahead of the main cold front ... creating at least weakly unstable profiles in the pre-frontal environment. Shear profiles should be sufficiently strong for severe evolution along and ahead of the cold front with 20+ m/s 0-6 km shear. Shear and SRH in the lowest km is advertised to be rather weak ... limiting the tornado threat ... but damaging wind gusts and large hail may occur with the stronger cells.

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