Storm Forecast
Valid: Thu 08 Sep 2011 06:00 to Fri 09 Sep 2011 06:00 UTC
Issued: Wed 07 Sep 2011 15:37
Forecaster: GATZEN

A level 1 was issued for the southern Baltic Sea region mainly for severe wind gusts.

A level 1 was issued for central Germany and southern Poland mainly for tornadoes.

SYNOPSIS

A broad ridge spreads into western Europe on Thursday. A strong mid-level jet streak will spread south-eastwards ahead of this ridge, leading to quasi-geostrophic forcing. At low levels, this will be associated with some moisture advection over Germany into Poland.

DISCUSSION

Southern Scandinavia, northern Germany, northern Poland, Baltic Sea and Baltic States

Main focus will be the strong mid-level jet streak spreading into northern Germany and the Czech Republic during the day. Strong quasi-geostrophic forcing is forecast at its cyclonically sheared flank. At lower levels, models indicate westerly to south-westerly winds that will advect a relatively warm and moist boundary-layer into north-eastern Germany, Poland, and the Baltic Sea. Given mostly neutral lapse rates, diurnal heating as well as low-level heating over the sea surface of the Baltic Sea will likely result in CAPE.

The best potential of thunderstorms is expected over southern Scandinavia near the base of the trough, where the instability will be deepest. Numerous showers and thunderstorms are forecast during the day. Weak vertical wind shear is expected and severe storms are not forecast, although waterspouts near the coasts are not ruled out.

Over northern Germany and Poland, the instability will be likely quite shallow at the southern edge of the mid-level trough. Showers and thunderstorms that form will have a potential to organize into bowing lines near the Baltic Sea, capable of producing severe wind gusts and marginally hail. A tornado is not ruled out given favorably veering profiles especially across northern Poland.

Central Germany to southern Poland

From central Germany to southern Poland, instability is forecast to be weak and shallow. However, showers and even thunderstorms may be possible given the rather rich low-level moisture and associated buoyancy. Showers are expected to spread south-eastward during the day. Given very strong vertical wind shear and favorably veering profiles ahead of the jet streak, tornadoes are not ruled out with these showers or thunderstorms. In the evening hours, decreasing instability and forcing will likely limit the severe potential.