Storm Forecast
Valid: Sun 09 Dec 2007 06:00 to Mon 10 Dec 2007 06:00 UTC
Issued: Sat 08 Dec 2007 15:27
Forecaster: DAHL

SYNOPSIS

Quite vigorous SFC low will track from Ireland to NW Germany during the period, while undergoing some weakening. As intense upper trough penetrates the NW Mediterranean, SFC cyclogenesis will result over the Gulf of Genoa along the cold front of the intense British cyclone. The Genoa cyclone will move to the N Balkans until Monday 06Z per latest numerical model guidance. Over the Ionian, and later over teh Aegean Sea, an upper cut-off low will be present, which will slowly accelerate eastwards.

DISCUSSION

... Mediterranean ...

Instability in the warm-sector air mass of the Genoa cyclone should remain quite weak, but shear profiles should be strong enough to favor isolated severe weather. Deep shear is simulated to be on the order of 20 to 25 m/s, and over Italy low-level shear should be greater than 10 m/s. This, coupled with a nearly a saturated boundary layer, suggests that a couple of mesocyclones, capable of brief/weak tornadoes, may occur. marginally severe hail/wind may also occur with the strongest cells. Bulk of activity should occur in the second half of the period.

Similar thermodynamic setup but less shear should exist over the Ionian/Aegean regions. However, especially along the Turkish west coast, isolated tornadoes may occur given increased LLS.

... France ... extreme S UK ... S Benelux ...

In the polar air mass over France and Benelux, comparatively shallow convection is anticipated. It seems that mesoscale forcing for ascent will be rather limited, and that the majority of the convection will fail to organize to any significant degree. However, quite large hodographs will be in place, and some shallow mesocyclones may occur. These will have some potential for spawning a brief tornado, along with marginally severe hail. Severe wind gusts are also likely, but these will be predominantly of non-convective nature.