CONVECTIVE FORECAST
VALID 06Z SUN 31/10 - 06Z MON 01/11 2004
ISSUED: 30/10 17:55Z
FORECASTER: DAHL

There is a slight risk of severe thunderstorms forecast across the central Mediterranean regions.

General thunderstorms are forecast across the Iberian Peninsula and the central Mediterranean.

General thunderstorms are forecast across the E Baltic States and the N Belarus.

SYNOPSIS

Elongated large-scale W-European upper trough is in the process of closing off into a cut-off low ... which will be centered over N Spain on Sunday per latest model guidance. Zonal upper frontal zone is will persist over NRN portions of Europe ... with imbedded vort maxima crossing the N Poland ... the Baltic States and the Belarus during the day. Ahead of the Iberian upper low ... several weak mesoscale frontal waves are expected to develop ahead of vort maxima at the E periphery of the upper low. Main ... fairly stationary front should stretch from E Algeria northwards across the central Mediterranean into the W Alpine regions throughout the period. NE European SFC low is expected move NE ahead of lifting NRN-stram upper trough.

DISCUSSION

...central Mediterranean...
Latest soundings do not show much instability over the central Mediterranean in the pre-frontal environment as the lapse rates havn't steepened by Saturday 12Z. Models continue to advertise advection of Saharan air atop the moist Mediterranean boundary layer ... but soundings from N Africa fail to exhibit a deep CBL. Hence ... CAPE may struggle to climb above 1000 J/kg on Sunday. Large-scale forcing for UVV's is progged to remain somewhat offset to the cool side of the front ... which may limit overall TSTM threat.

Shear profiles will continue to be supportive to severe TSTMS with about with 10 to 15 m/s 0-1 km shear ... and 15 to 20 m/s deep shear. Storms in this environment will likely have the potential to become supercellular and produce severe wind gusts ... large hail and tornadoes given low LCLs and strong low-level shear.

Coverage may be somewhat limited owing to the lack of concentrated large-scale UVV's ... but precip forecasts ... and the presence of mesoscale wave cyclones suggest that widespread convection may be possible.

......
A few TSTMS may continue within theta-e tongue ahead of E-European low. 20 to 25 m/s deep-layer shear and 10+ m/s 0-1 km shear may promote an isolated severe TSTM event ... mainly marginally severe hail and damaging winds. Threat should weaken during the day as boundary layer air mass becomes increasingly less unstable.

#