Storm Forecast
Valid: Thu 22 Jun 2006 06:00 to Fri 23 Jun 2006 06:00 UTC
Issued: Wed 21 Jun 2006 20:11
Forecaster: GATZEN

SYNOPSIS

Strong upper trough will move over the North Sea ... and strong jet streak is expected from western North Sea to northern Germany and further to Baltic Sea region ... where 500 hPa winds will likely reach more than 30 m/s. Over eastern Europe ... high-over-low blocking remains ... and weak winds are expected in the mid-troposphere. Over Mediterranean ... a jet streak is expected to travel eastwards. At lower levels ... stable airmass has entered Germany behind a cold front and spreads eastward into Poland ... and Baltic Sea region. To the east and south ... unstable airmass is expected especially from southeastern Poland to northern Balkans ... where EML indicated by latest soundings should be present ... with lapse rates of 8-9K/km between the 900 and 700 hPa-level. Given rich boundary-layer moisture today over Poland, Czech Republic, Slowakia, and northern Balkans ... CAPE will likely reach 1000-2000 J/kg during the forecast period.


DISCUSSION

Southeastern Germany, Austria, Slowakia, southeastern Poland, northern Balkans

Strong instability will be present as indicated by latest soundings and model forecasts east of a cold front. In the mid-troposphere ... delta-flow pattern is forecast at the southeastern flank of northern European trough. In the range of this delta ... weak winds are expected by latest models ... and it seems that DLS will be weak as well. Diurnal heating and low-level forcing along old outflow boundaries and along propagating cold front should lead to initiation ... especially in the afternoon hours as weak vort-max/short-wave trough reaches the region. Although vertical wind shear should be weak ... complex low-level wind field east of the cold front as well as low LCL heights seem to support a few rotating updrafts ... and isolated large hail and probably a tornado is not ruled out. There is also a threat of severe wind gusts due to strong downdrafts. Thunderstorms should cluster during the day ... and intense precipitation should lead to local flash flooding.

Eastern Baltic Sea region

Northern branch of unstable airmass is expected ahead of the cold front from central Poland to Baltic states. Amount of instability will be lower than over the Balkans ... but rather steep lapse rates and rich boundary-layer moisture should lead to CAPE in the order of 500-1000 J/kg. Along the cold front ... thunderstorms should go on during the period from central Poland to northern Baltic States. Just west of the front ... vertical wind shear is forecast to reach 20 m/s DLS ... and it is expected that some vertical wind shear should be available to the storms along the cold front ... that should organize into multicells and mesocyclones ... capable of producing large hail and severe wind gusts. As low-level shear should be enhanced as well ... and given quite low LCL heights ... a few tornadoes are not ruled out.