Storm Forecast
Valid: Thu 22 Nov 2007 06:00 to Fri 23 Nov 2007 06:00 UTC
Issued: Wed 21 Nov 2007 19:35
Forecaster: GATZEN

SYNOPSIS / DISCUSSION

Weakening trough over west Europe remains. At the eastern flank, warm air mass advects into central Europe. This air mass is mostly stable as indicated by latest ascends. Rather cool boundary-layer is capped over west Mediterranean, while almost now instability is expected over France and further north.

On Thursday, some QG forcing is expected over southern France region underneath the anticyclonic flank of an upper-level jet streak that propagates northward. Along the frontal boundary cyclogenesis is forecast and rather strong lift may be sufficient for some instability to develop. Given rather poor low-level buoyancy, strong convection is not expected at this time. Stratiform precipitation and embedded thunderstorms are forecast. However, latest model output suggests rather strong low-level veering profiles in the warm sector of the developing wave, and will not rule out embedded mesocyclones, capable of producing a tornado. Best potential seem to exist over south-eastern France. Threat is too low for a level 1, though.

Over west Mediterranean as well as over Bay of Biscay, and in the range of southern Portugal, cool air mass will become slightly unstable as the upper trough propagates eastward. Weak vertical wind shear is forecast, and a few waterspouts are not ruled.