CONVECTIVE FORECAST
VALID 06Z SUN 02/05 - 06Z MON 03/05 2004
ISSUED: 01/05 18:10Z
FORECASTER: DAHL

General thunderstorms are forecast across SW ... SE and E-central Europe.

SYNOPSIS

As extensive SW European upper low is phasing with a digging N Atlantic trough ... it will slowly accelerate east with peripheral vort maxima overspreading E Spain and the SW Mediterranean Sea late on Sunday. Weak upper trough over the central/E Mediterranean is expected to make little eastward progress. Much of central Europe will remain in quiescent conditions.

DISCUSSION

...Central Europe ... Eastern Europe ... Central Mediterranean ...
Air mass over much of central and SE Europe as well as over the central Mediterranean regions is nearly uncapped and marginally unstable. Some of Saturday afternoon launches indicate deep dry-adiabatically mixed subcloud layers. This general thermodynamic setup is expected to remain nearly unchanged acorss most of Europe through Sunday.

TSTMS should mainly be driven by diurnal heating ... though 500 hPa analyses reveal weak vorticity maxima over central Europe ... the central Med and SE Europe ... which may augment convective activity. Orographic forcing will likely turn out to be instrumental in initiating TSTMS over much SE-central Europe and the Balkan States as well as over the Italian Peninsula. However ... weak large-scale ridging may limit depth of convection over the central Mediterranean/Italy and W Balkan. Given weak capping ... coverage of convection may again be rather high ... and cells may interact with the various outflow boundaries of neighboring storms ... locally enhancing the low-level shear profiles. Also ... weak low-level baroclinic zone over E-central Europe may strengthen low-level shear somewhat ... and a brief mesocyclone or two cannot be discounted despite the weak large-scale setup. Primary threat with these storms will be marginally severe hail. Locally deep boundary layers will promote gusty outflow winds ... which may isolated approach severe levels. Nonetheless ... allover threat of severe TSTMS is quite low ... and refraining from issuing categorical severe given the marginal setup and expected isolated nature of /marginal/ SVR TSTM events. Owing to relatively slow storm motion ... high amounts of precip will locally be possible.

...SW Mediterranean...
Strong vort max rotating about the SW-European upper low will cross S Iberia and the SW Mediterranean lare in the period. Ahead of this feature ... mixed north Saharan air mass will overspread the SW Mediterranean. Saturday's DAAY 12Z ascent shows rather shallow SFC-based mixed layer though ... rendering mean lapse rates relatively weak. It thus appears that the thermodynamic setup will be quite marginal over the SW Mediterranean ahead of the trough ... and it is questionable whether TSTMS will develop at all. Deep-layer shear will likely be on the order of 20 to 25 m/s ... and a few severe TSTM events could occur ... if storms initiated. Situation will be monitored for possible upgrades.

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