CONVECTIVE FORECAST
VALID 06Z SUN 14/12 - 06Z MON 15/12 2003
ISSUED: 13/12 20:57Z
FORECASTER: DAHL

There is a slight risk of severe thunderstorms forecast across BeNeLux ... Germany ... E Poland ... W Chech Republic.

General thunderstorms are forecast across Central Europe.

General thunderstorms are forecast across the Aegean Sea.

SYNOPSIS

Fast meandering upper zonal flow is present over the North Atlantic and the central/northern portions of Europe ... Vort max at the W periphery of digging upper trough ATTM over the North Sea ... will rapidly cross central and eastern Europe during the forecast period. Towards the end of the FCST period ... large longwave trough will cover the eastern half of the forecast area ... with adjacent upstream upper long-wave ridge extending across the E Atlantic and E Europe. Cold front associated with the mean trough ATTM over the North Sea ... is progged to stretch from west France across the Alps into the S Baltic States by Sunday 06Z ... and extend from the SW Mediterranean acroos the Aegean Sea into the W Black Sea towards the end of this period. Central Mediterranean upper low is expected to weaken and to accelerate eastwards to be ingested by the digging longwave trough late Sunday night/Monday morning.

DISCUSSION

...Central Eruope...
Sunday's convective scenario will be a bit of a challange ... one of the foci for potentially severe evolution is the post-frontal environment over central Europe. Models coherently assume intensifying elongated DCVA maximum in the wake of the main DCVA max over the cold front ... as also indicated by latest IR and WV imagery. Indications are that field of enhanced Cu's will develop during the period over east-central Germany ... possibly developing into a line of convection a few hundred kilometers behind the main cold front. Gradient flow at the SFC will likely exceed 50 knots locally ... and winds would be augmented by vertical momentum transfer along this line.

500 hPa vorticity fields ... and 500/300 hPa vorticity-advection fields suggest several small vort maxima which will cross the North Sea ... BeNeLux and Germany during the day. These features are coherently simulated by several models (GFS, GME, MM5, MESO ETA). Concomitant meso-scale vertical motion fields will likely favor regions of relatively deep convection/TSTMS ... posing mainly a threat of augmenting severe gradient flow. However ... primarily isolated cells will also have some potential of acquiring rotation if regions of orographically induced high SRH are encountered ... and an isolated threat of marginally severe hail and maybe a brief tornado exists.

...Mediterranean...
TSTMS will likely continue ahead and underneath of the closed upper low over the Aegean Sea ... but generally weak thermodynamic and kinematic fields should limit severe potential. Farther northwest ... CAPE is expected to remain negative in the pre-frontal airmass and TSTMS appear to be rather unlikely. Shallow convection could occur in the wake of the cold front especially over the Adriatic ... but TSTMS are not expected ATTM.

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