Forecast Update
Valid: Mon 14 May 2007 10:00 to Tue 15 May 2007 06:00 UTC
Issued: Mon 14 May 2007 10:15
Forecaster: GROENEMEIJER

SYNOPSIS

Refer to convective forecast, with the addition that a rather well-defined baroclinic wave is expected to develop over E France during the morning, travelling northeastward to the Baltic Sea overnight.

DISCUSSION

Germany, Czech, Poland...

The more pronounced development of the aformentioned baroclinic wave has required this update/upgrade. As the wave travels northeastward, very favourable and strongly helical flow is expected within its warm sector.
The centre of the associated surface low should form over Swrn Germany and travel NEward putting the indicated level 2 area most at risk. Confidence in this development is increased by the fact that both GFS and UKMO support it.
Any storms developing within the helical environment east of the surface low that should have 0-3 km SRH of 300-400 m2/s2, will rapidly become supercells. The amount of latent instability that will be realized should be rather limited with values of around 500 J/kg MLCAPE, even though GFS is suggesting far higher values because it likely overestimates low-level moisture.
The main threat of the convective storms should be large hail in the east of the area. Tornadoes are possible, too, mainly in the northwestern part of the risk area where LCL heights should be the lowest.
Isolated storm may produce a few severe gusts locally, but the threat should increase later if storms manage to organize into and MCS. Potential exists for a bowing MCS to develop over E Germany, W Czech and or W Poland during the evening hours.

SE France...

Strong shear and helical flow over SE France combined with low instability is sustaining a couple of supercells east of the frontal stratiform precipiation. The environment looks supportive of tornadoes until 14 UTC.