Storm Forecast
Valid: Tue 13 Nov 2007 06:00 to Wed 14 Nov 2007 06:00 UTC
Issued: Tue 13 Nov 2007 02:15
Forecaster: VAN DER VELDE

SYNOPSIS

A chain of low pressure cores is found from the North Sea to the southern Baltic Sea to western Russia. The air mass is cold and slightly unstable over central and eastern Europe, so that showers can develop. In some places these may be weakly electrified. In coastal areas of the Baltic Sea, southern North Sea and the Danish coastal waters within the trough waterspouts may occur, but due to lack of CAPE the chances are only marginal. Same for the Mediterranean coasts, e.g. Wrn/Srn-Italy, Greece and Turkey. Deep layer shear is enhanced here to fine values (>15-20 m/s), but lack of forcing and lack of significant instability ought to be insufficient for severe weather.

DISCUSSION

The most active system deepens over the western North Sea into a low, with increasingly unstable air advected from sea into western Netherlands and Belgium. Positioning at the western flank of an upper jet and the nose of a midlevel PV anomaly, strong forcing is present. Instability is mostly present east of the jet axis, but significant low level shear (>10-12 m/s) spreads a larger area. LCL heights are also very low (<500m) so a chance of an isolated short-lived tornado appears to exist. SREH is present, but better represented eastward in the area of warm air advection.
The chances for some lightning and sporadic severe weather chance advect with the system into France and the Alps by evening and midnight at the well-defined nose of midlevel vorticity and GFS most-unstable EL height signals (<-20°C).