Storm Forecast
Valid: Mon 15 Jun 2009 06:00 to Tue 16 Jun 2009 06:00 UTC
Issued: Sun 14 Jun 2009 22:05
Forecaster: DAHL

A level 1 was issued across SE France ... S Germany ... parts of Austria ... Switzerland ... Czech Republic mainly for severe hail ... damaging wind gusts, and for tornadoes.

A level 1 was issued across W Russia mainly for tornadoes, excessive rainfall, and large hail.

SYNOPSIS

The E-Atlantic upper long-wave trough will close off into a cut-off cyclone, with the remnant short-wave trough accelerating eastwards, reaching N-central Europe late on Monday. Plume of warm/unstable air is advecting northwards ahead of this feature, and a wave cyclone is expected to develop ahead of the trough over E France early in the period. This cyclone will travel along the NW edge of the theta-e tongue, crossing Germany during in the day.
A fairly intense SFC-low complex persists over Scandinavia. Otherwise, synoptic SFC conditions are rather quiescent.

DISCUSSION

... E France ... southern half of Germany ...

Current simulations indicate that extensive cloudiness and precipitation will exist in the warm-sector air mass. This suggests that the air will struggle to destabilize, and the majority of the convection may be of elevated nature. However, gaps in the clouds may occur, over SE Germany maybe owing to temporary Foehn efffects. However, CAPE is generally expected to be quite weak for boundary-layer parcels and may be restricted to mid-level parcels.

Shear profiles will be rather inpressive with 30 m/s DLS and, towards the evening and over S Germany and E France, 10 m/s LLS. SRH3 will generally be on the order of 200 J/kg over extreme S Germany per GFS.

Currently it does not seem likely that widespread SFC-based convection will develop. Rather, elevated/imbedded cells should be the dominant mode. These cells could still be capable of marginally severe hail given rather strong effective shear. However, some cells will likely become SFC-based. Their effective kinematic environment will be more than sufficient for supercells, capable of large hail and damaging wind gusts. Especially towards the evening and from E France into S Germany, tornadoes are possible given the enhanced LLS.

Main uncertainty is the evolution of the thermodynamic fields and the likelihood of SFC-based convection. Will remain somewhat conservative and issue a LVL1 threat, though a LVL2 may become necessary, should the thermodynamics evolve more favorably than currently anticipated.

... W Russia ...

Moderate and weakly-capped instability should persist in warm/moist air tongue wrapping around the Scandinavian low-pressure system. Deep shear is not expected to be particularly strong, but LLS well in excess of 10 m/s is advertised by GFS, which implies that at least comparatively short-lived supercells with a threat of tornadoes and marginally severe hail exists. Slow storm motion and large storm coverage may locally result in excessive rainfall.

... Iberia ...

Scattered high-based storms will likely develop over the Iberian peninsula during peak-heating hours. Deep CBL will likely support strong/severe outflow winds, but coverage should remain too low for a categorical risk.