CONVECTIVE FORECAST
VALID 06Z SUN 17/10 - 06Z MON 18/10 2004
ISSUED: 16/10 17:54Z
FORECASTER: DAHL

General thunderstorms are forecast across E Europe ... the Balkan States and the central Mediterranean.

General thunderstorms are forecast across N-central Europe

SYNOPSIS

Models are in agreement that the extensive upper low centered over central Europe will make little eastward progress. As Atlantic upper trough digs southward ... upper flow over SW Europe will back somewhat ... yielding broad strong upper WSWLY flow from the Azores to the Ukraine by Monday 06Z. Large SFC low covering much of Europe ... with several smaller lows existing at the periphery which are associated with vort maxima orbiting around the main upper low. Relatively strong cyclogenesis is advertised over the southern Baltic Sea and over SE/E Europe on Sunday.

Uncertainty with this forecast is quite high given the widespread combination of nearly neutral lapse rates and strong dynamic forcing for upward motion as well as strong shear ... which could easily create an environment conductive to severe deep convection. Current data do not allow for too much specification as to where this will happen ... or if it will happen at all.

DISCUSSION

...Romania ... S Ukraine...
Cold front trailing from the developing E-European SFC low ... is expected to surge eastwards across Romania and the S Ukraine late in the day. Existence of positive CAPE this far north is quite uncertain ... but strong forcing and shear will aid any TSTM that does form in becoming organized ... and possibly severe. Main threats will be severe wind gusts ... but a few mesocyclones may also form ... posing an additional threat for large hail and a tornado or two. Uncertainties as to the presence of CAPE preclude SLGT ATTM.

...central Mediterranean ... S Balkans...
Weak CAPE is progged to persist within theta-e plume over the central Mediterranean and the S Balkans. Lack of large-scale forcing for UVV's should limit TSTM threat ... though especially along the Adriatic coast some TSTMS may form in upslope-flow regime. An isolated hail/wind event exceeding severe levels could occur ... but allover severe threat looks to be rather low.

Slim chances for rather shallow post-frontal TSTMS exists over N Italy and the very N Mediterranean Sea late in the evening ahead of small vort max. Given strong shear ... isolated/brief severe evolution cannot be excluded though likelihood remains rather low.

...north-central Europe...
Scattered TSTMS may occur in associaton with shallow convection beneath the central Europen upper thermal low ... but current thinking is that magnitude of the TSTM threat does not warrant a large TSTM area ATTM. Will place a TSTM area S of developing SFC low where depth of convective mixing may be enhanced. Also ... increasing low-level shear may promote briefly rotating updrafts. ATTM however ... confidence is low that this scenario unfolds.

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