Storm Forecast
Valid: Thu 10 Jan 2008 06:00 to Fri 11 Jan 2008 06:00 UTC
Issued: Wed 09 Jan 2008 22:40
Forecaster: GATZEN

SYNOPSIS

North-east European high remains, while the trough over north-western Europe amplifies. This is associated with strong cyclogenesis over Bay of Biscay on Thursday. To the north, weakening low-pressure systems affect British Isles, the North Sea, and Scandinavia.

DISCUSSION

Western Scandinavia

Maritime air mass characterized by neutral lapse rates and rich boundary-layer moisture is advected eastward into southern Scandinavia. Upslope flow and low-level convergence as well as QG forcing associated with a strong upper jet spreading into southern Scandinavia will likely lead to convection during the period along the west coast. Showers and a few isolated thunderstorms are forecast. Given strong low-level vertical wind shear near the coast, severe wind gusts are forecast with strong downdrafts. As low-level veering and buoyancy is not too strong, tornadoes are not forecast.

Bay of Biscay

Strong cyclogensis is forecast by latest models over Bay of Biscay. In the range of the warm sector of the developing storm, warm maritime air mass spreads into Bay of Biscay. This air mass will likely be characterized by neutral lapse rates and rich moisture. It seems that a strong upper short-wave trough/jet streak will spread across the cold front in the night hours, and strong QG forcing may affect the moist air mass. Latest models indicate large-scale precipitation, but the development of a convective line long the cold front seems to be possible. Severe wind gusts will be the main threat. However, given strongly veering profiles and 400 J/kg 0-1 km SRH, tornadoes are also forecast along and ahead of the cold front. Even strong tornadoes may be possible, but given uncertainties about the development of the surface pressure field, will only issue a level one at this time.