CONVECTIVE FORECAST
VALID Fri 19 Aug 06:00 - Sat 20 Aug 06:00 2005 (UTC)
ISSUED: 18 Aug 17:32 (UTC)
FORECASTER: TUSCHY

There is a slight risk of severe thunderstorms forecast across parts of Ukraine,Moldova and extreme eastern Romania

SYNOPSIS

Intense trough over northwestern Europe will shift southward during the next 24 hours because of a strong jet streak entering the trough from the northwest...This will help to introduce a slow eastward shift of an high pressure area downstream of this system over northeastern Europe, but over-all split-flow configuration with two strong jet branches will persist over most parts of Europe...Another trough is located west of the Black Sea area and should shift slowly southeastward.

DISCUSSION

...parts of Ukraine,Moldova and extreme eastern Romania...
Upper level trough will help to disequilibrate the atmosphere with about 500 J/kg MLCAPE...Although DLS will be fairly weak, low level shear should be enhanced with up to 10m/s, especially along the southeastward moving cold front...Current thinking is that widespread TSTMs will develop during the time period in an environment with low CIN values...Storms should cluster and main risk will be torrential rainfall and strong to isolated severe wind gusts...Evapotranspiratively moistened boundary layer should be conducive for a pretty low LCL distribution and this, combined with the enhanced low level shear values, will pose a risk for a slight increase in possible tornado development... and will be finally the main reason for issuing a marginal SLGT risk in this area.

...eastern Spain and most parts of the Balearic Sea...
Amplifying upper level trough will arrive in this area during the early night hours accompanied by a cooler mid- and upper level airmass... GFS output with about 600 J/kg of instability looks reasonable and scattered storms should develop in this area...15 to about 20m/s DLS will be enough for storm organisation with main risk being severe wind gusts and isolated large hail [ enhanced hail risk especially over eastern parts of Spain with higher LCL values ].

...Germany,Switzerland and parts of eastern France...
Main focus for TSTM development will be an eastward moving cold front and/or preliminary convergence zone...Environment only marginal unstable with about 300 J/kg and kinematic parameters don't look that impressive with not even ~ 15m/s DLS...Because of slow eastward propagation of the cold front (aligned nearly parallel to background flow), main risk will be a flash flood threat, especially in areas with training storm development and isolated severe wind gusts during maturing phase of storms.

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