CONVECTIVE FORECAST
VALID 06Z SUN 11/01 - 06Z MON 12/01 2004
ISSUED: 10/01 23:16Z
FORECASTER: DAHL

General thunderstorms are forecast across the British Isles into central Europe.

General thunderstorms are forecast across the central Mediterranean regions.

SYNOPSIS

Quite impressive zonal jet stream over the Atlantic is rapidly propagating eastwards ... and will stretch all the way from the US across the Atlantic into central Europe. Band of strong DCVA will accompany the nose of the jet ... this band will become coupled with low-level cold front ATTM extending from the Atlantic northeastwards to the northern British Isles ... and which is trailing from complex SFC low-pressure system covering large parts of the N Atlantic. Somewhat incoherently simulated small perturbation amidst the upper jet is expected to lead to very intense cyclonenesis late Sunday night/early Monday morning over the N France/S Great Britain. Vort max ATTM over the Adriatic will rapidly pivot around the base of an eastern European upper long-wave trough and affect the south-central Mediterranean Sea on Sunday. SFC low ATTM over the S Aegean ... will slowly track eastwards along the Turkish S coast.

DISCUSSION

...France ... BeNeLux ... Germany...

Challange of the day will be possible convection along the cold font which will cross central Europe during Sunday. Seasonably stable warm-sector air mass will not be particularly supportive to deep free convection ... but chance appears to exist that small-scale zone of strong ascent could develop along the leading edge of the SFC front. Associated forced line convection may well produce a few lightning strikes ... and could act to transfer strong low/mid-level horizontal momentum downward ... which may cause severe straight-line winds at the surface. 0-3 km SRH will be on the order of 400 m2/s2 per GFS output ... but supercells appear unlikely as convection should be linear. This scenario is quite conditional ... but situation will be monitored and severe threat will be specified with later outlooks.

British Isles ... North Sea ... BeNeLux ... N Germany

Field of deep cellular convection is present in the wake of the cold front and has produced fair amount of CG's W of the British Isles ... Deepest convection will likely be present over the central parts of the British Isles on Sunday and move into the North Sea ... and may continue to produce some lightning strikes. Very gusty winds and small hail may accompany the stronger cells. Less deep convection may spread into Benelux ... W and N Germany late in the day/evening ... However ... there does not appear to much upper support and TSTM threat looks to be too small for a large GEN THUNDER area at the moment.

NW France ... S Great Britain

Majority of the models suggests rapid development of very intense/small SFC cyclone over S UK late in the period. Possibly small unsampled sheets of weak instability ... or strong forced ascent along the leading edge of the front have led to convective development in similar past situations ... and could again account for convective development. This is entirely speculative ATTM ... and will await later obs to identify possible foci for convective development with this feature.

...Mediterranean...
TSTMS are expected to continue over the south-central Mediterranean ahead of the vort max at the periphery of the mean trough ... and over the Aegean and SW Turkey beneath the upper cold pool. Overall shear is rather weak ... as are the thermodynamic parameters ... and organized severe TSTM threat is rather small.

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