Forecast Update
Valid: Thu 07 Dec 2006 13:00 to Fri 08 Dec 2006 06:00 UTC
Issued: Thu 07 Dec 2006 13:46
Forecaster: GROENEMEIJER

SYNOPSIS

Refer to convective forecast.

DISCUSSION

NWrn France, Benelux, nWrn Germany, Denmark

A frontal system, followed by a shallow moist zone currently over the North Sea is expected to move further northeastward during the remainder of the forecast period. The shallow moist zone is characterized by very strong low-level shear of 15 m/s in the 0-1 km layer and considerable buoyancy below an inversion around 4 km A.G.L.
Ongoing, locally thundering, convection has produced a tornado over northern London. As the associated frontal and upper-level weather systems move northeastward, additional storms with an attendant tornadic threat are possible. Hence, a level 1 appears to be warranted for the indicated area.
Threat should be much lower in the sheared environment further west, where low-level air is drier.