CONVECTIVE FORECAST
VALID 06Z SAT 02/10 - 06Z SUN 03/10 2004
ISSUED: 01/10 18:16Z
FORECASTER: DAHL

General thunderstorms are forecast across British Isles and the North Sea.

General thunderstorms are forecast across Bulgaria ... S Romania and the W Black Sea.

SYNOPSIS

Large-scale upper low over the N Atlantic is progged to expand eastwards as vort maxima pivot about its periphery ... affecting NW-central Europe late in the period. Upper high will remain in place across Scandinavia ... with low geopotential persisting over E and SE Europe. S of this omega configuration ... zonal upper frontal zone is extending across France ... the N Mediterannean into Turkey. Weak vort max imbedded in this flow is progged to merge with SE European trough on Saturday. At the SFC ... main feauture will be large SFC low centered between Iceland the the British Isles ... and weak/large SFC high over N Europe. Otherwise ... pressure distribution is quite flat.

DISCUSSION

...British Isles...
Ahead of vort max currently over the N Atlantic ... field of enhanced cumuli is present ... which should spread across the UK on Saturday ... and possibly into the North Sea and NW Holland as well as Denmark towards early Sunday morning. Over the British Isles ... shear in the cloud-bearing layer should be on the order of 35 m/s ... with 10+ m/s shear in the lowest km. Expect a few short ... briefly bowing ... lines of TSTMS as well as small/shallow mesocyclones ... posing threat for isolated marginally severe wind/hail events and possibly a brief tornado or two. Threat appears to be too marginal for a SLGT ATTM.

...Bulgaria ... S Romania and the W Black Sea...
Weak frontal boundary should stretch across central Balkan States on Saturday ... roughly parallel to the Balkan W coast. The air mass to the SW of this boundary should be weakly unstable as hinted at by GFS and NMM22. As vort max merges with the upper trough ... it is expected to graze N Bulgaria ... and sufficient UVVs could be created for TSTMS to initiate. However ... current thinking is that any activity will be quite isolated. The strongest cells could produce some hail and strong wind gusts given moderately strong shear ... but weak thermodynamic support and allover marginal setup should limit severe TSTM threat.

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