Storm Forecast
Valid: Sun 03 Dec 2006 06:00 to Mon 04 Dec 2006 06:00 UTC
Issued: Sun 03 Dec 2006 00:00
Forecaster: GROENEMEIJER

SYNOPSIS

Sunday at 06:00 UTC a meandering westerly mid-level flow is present over Europe. An intense trough just west of the British Isles induces rapid cyclogenesis northwest of Scotland. Downstream, a WSWly flow is present over Northern Europe. An elongated ridge extends from Belarus to Egypt.

DISCUSSION

British Isles...

A frontal system is expected to be located over western Great Britain and extends southward via western Brittany to NWrn Spain. The frontal system is followed by a number of showers, some weakly electrified. Some 4 to 6 hours after passage of the frontal system, a surface trough is expected to affect Ireland and Great Britain. One or more squall-lines are forecast at the passage of the trough. At this time, a low-level wind maximum of near 40 m/s at 850 hPa should cross Ireland simultaneously. Wind gusts of near that speed appear possible at the surface as well. Given that anticipated values of 0-1 km SRH around 300 m2/s2 are advertised by the 12Z GFS run, and the overall strong shear, it appears that a few tornadoes may occur as well. This will, however, strongly depend on the hard-to-forecast quantity of buoyancy in the lowest few kilometres of the troposphere. If tornadoes occur, the extreme low-level shear suggests that they may be strong, F2+. The trough should move into Ireland around 9:00 UTC and should reach northern England, Wales and southwestern Scotland approximately at 15:00 UTC, before gradually decaying during the evening as it moves further east. The main threat of severe and extremely severe winds warrants at least a level 2. If low-level winds turn out to be even stronger than currently forecast, an upgrade to level 3 may be issued later.