CONVECTIVE FORECAST
VALID 06Z THU 23/09 - 06Z FRI 24/09 2004
ISSUED: 22/09 16:58Z
FORECASTER: GATZEN

General thunderstorms are forecast across southern North- and Baltic Sea region, northern Germany, central Ukraine, southern Iberian Peninsula

SYNOPSIS

South of intense trough over northern Europe ... a very strong upper jet stream reaches from the Atlantic south of Iceland to Great Britain ... Central Europe ... northern Balkans ... western Russia ... eastern Scandinavia. Several strong jet streaks (50+ m/s @ 500 hPa) are forecast to move rapidly eastward ... while upper long wave trough expands southward. Over the Mediterranean ... synoptic scale sinking is expected at the anticyclonic flank of the upper jet.

DISCUSSION

...North-central Europe ...
A very strong jet streak/vort-max south of Iceland is expected to move southeastward reaching the Alpine region on early Friday. At lower levels ... a well defined frontal boundary is present over the northeastern Atlantic Ocean ... and a frontal wave will move SE-ward crossing Germany during the forecast period. Convective activity is expected to the north of this wave ... where convectively mixed maritime airmass will destabilize during the day in the range of the vort-max. Showers and thunderstorms are forecast. While deep vertical wind shear will be relatively low as indicated by latest model output ... organized thunderstorms are not likely. Very strong vertical wind shear in the range of the upper jet should not overlap the region of convective activity. However ... due to the large pressure gradient ... showers and thunderstorms will be accompanied by strong or severe wind gusts which are not primarily caused by the convection. Small hail/soft hail is also forecast. Best chance for organized convection is expected over the southern North Sea and Benelux/northern Germany ... where models indicate increasing SRH in the range of the trough axis. Isolated large hail, severe wind gusts and brief tornadoes are not ruled out if thunderstorms will organize.

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