Storm Forecast
Valid: Wed 20 Sep 2006 06:00 to Thu 21 Sep 2006 06:00 UTC
Issued: Tue 19 Sep 2006 19:25
Forecaster: GATZEN

SYNOPSIS

East of strong long-wave trough over Atlantic Ocean ... relatively high geopotential covers Europe. An embedded trough present over eastern Europe slowly moves eastward ... and rather cool air mass has entered Mediterranean. To the west ... strong WAA sets in over western Europe: Warm and dry air mass spreads northward into North Sea region in the range of amplifying high ... while tropical air mass originating from Hurrican Gordon spreads north-eastward in the range of the frontal zone from eastern Atlantic to Ireland. Over northern Europe ... strong upper jet/frontal zone has formed over northern Scandinavia ... and well-developed upper trough moves eastward.

DISCUSSION

Finland, Baltic States, western Russia, north-eastern Poland

To the south of strong frontal boundary over northern Scandinavia ... a cold front travels eastward over Finland ... replacing warm subtropical air mass by maritime air mass. Both air masses are characterized by neutral to slightly unstable lapse rates and rich low-level moisture ... and soundings over North Sea region (cold air mass) and southern Baltic Sea (warm air mass) indicate CAPE and weak CIN. Models show that warm air mass will spread into eastern Poland, Baltic States and Finland east of the cold front. On Wednesday, 06Z, cold front is already expected over southern Finland and north-eastern Poland ... quickly spreading eastward. It is rather questionable that warm air mass will reach the boundary layer over the northern portions due to bad timing and weak insolation ahead of the front. However ... strong low-level convergence as well as QG forcing may lead to deep convection along the cold front that may organize into a shallow line given strong vertical wind shear over Finland/Russia. To the south ... vertical wind shear gradually decreases, while chance for thunderstorms will increase. It is expected that a few severe wind gusts will occur over Finland, Russia, and the Baltic states and maybe northern Poland along the cold front. In the wake of the front ... maritime air mass spreads into Finland that should be quite moist. An upper trough axis travels eastward that should lead to linear forcing due to DCVA. However ... latest models do show that CAA in the wake of the front should be too strong ... and QG forcing won't be favorable for deep convection. Current thinking is that showers/thunderstorms will not develop. However ... situation has to be monitored as vertical wind shear will be favorable for organized convection west of the cold front ... and maritime air mass may be unstable in the range of the trough axis.

Adriatic Sea, Aegean Sea, Black Sea

As on Tuesday ... absence of strong flow and presence of moist airmass and steep low-level lapse rates may give rise to a number of waterspouts where convection concentrates by low-level convergence. Chance should be weaker than on Tuesday as upper trough weakens.