Storm Forecast
Valid: Sat 09 Dec 2006 06:00 to Sun 10 Dec 2006 06:00 UTC
Issued: Fri 08 Dec 2006 22:56
Forecaster: DAHL
SYNOPSIS
W European upper long-wave trough will make some eastward progress and become somewhat deformed by amplifying vort max at its W periphery by the end of the period. Associated main low-level frontal boundary is slowly moving east, stretching from the central Mediterranean across E-central Europe into Finland by Saturday 12Z. N European/Atlantic SFC low complex is expected to undergo some weakening, including peripheral wave cyclone expected over S Scandinavia at the beginning of the forecast period. N Mediterranean SFC low is progged to fill as well during the day.
DISCUSSION
... central/north Mediterranean ... Italy ...
Scattered TSTMS will likely accompany vort maxima which are expected to overspread the pre-frontal air mass over the N and central Mediterranean regions. Robust shear profiles will remain in place per model guidance and despite minimal CAPE, some thunderstorms will have the potential of becoming severe. Main threat should be severe outflow winds, though strong low-level shear, partly strong low-level buoyancy and low LCL heights should also favor tornadoes.
... Gulf of Biscay ... France ... NW Mediterranean Sea ...
In the deep polar air mass W of the main cold front, scattered TSTMS should spread eastward from E Atlantic/Gulf of Biscay and the western portions of France, into the NW Mediterranean during the period. Especially over France, the shear profiles will likely be rather strong and an isolated mesocyclone or two, with an attendant tornado threat, cannot be excluded. However, the lack of focused mesoscale forcing for ascent as well as rather straight-line hodographs should limit the overall severe convective threat. Also, lack of SFC heating may limit the coverage of the storms over France and a categorical risk does not seem to be necessary at the moment. Especially over the Mediterranean Sea, a few water spouts may occur.
A few CGs may also accompany the convection over the North Sea but current indications are that activity will remain too shallow to warrant a TSTM area.
