Storm Forecast
Valid: Wed 13 Dec 2006 06:00 to Thu 14 Dec 2006 06:00 UTC
Issued: Tue 12 Dec 2006 20:33
Forecaster: GATZEN

SYNOPSIS

Zonal flow is present over Europe north of a broad high that spreads over western, central, and south-eastern Europe. At the southern flank of this high, a well-developed cut-off low slowly propagates eastward over northern Algeria. Over northern Europe, a trough moves eastward over north-eastern Europe, while strong south-westerly flow and warm air advection dominate over north-western and northern Europe. Instability is not expected by latest models over most of Europe during the forecast period. Strong cyclogenesis is expected south of Iceland.

DISCUSSION

Northern Algeria, Tunisia

In the range of the strong cut-off low, cold air mass has spread into western Mediterranean, and latest soundings indicate steep low-level lapse rates above the relatively warm sea surface. Some showers and thunderstorms may form over western Mediterranean. Best potential is expected over northern Algeria and Tunisia, where orographic lift and approaching strong southerly jet streak supports convection. Especially in the range of the northern coast of Tunisia, increasing and deepening instability is forecast during the period, as latest models indicate a tongue of rather moist maritime air mass, advecting westward at low levels. Thunderstorms are likely to develop. Especially near the coasts, vertical wind shear will increase during the day. Easterly surface winds and strong southerly jet aloft are forecast to create rather high helicity, and it is expected that a few thunderstorms will organize, capable of producing severe wind gusts, isolated large hail, and a few tornadoes. Convection is expected to develop over a widespread region, moving northward, and continuing during the night hours.