Storm Forecast
Valid: Thu 04 Oct 2007 06:00 to Fri 05 Oct 2007 06:00 UTC
Issued: Wed 03 Oct 2007 20:40
Forecaster: GATZEN

SYNOPSIS

The two weakening cut-off lows over Iberian Peninsula and southern Turkey remain. In the range of both troughs, instability has significantly increased during the last day. Latest Palma de Mallorca sounding indicates more than 1500 J/kg CAPE. A well-mixed warm air mass originating from the Atlas and moist maritime air mass in the boundary layer lead to this instability. Small troughs slowly propagate eastward over North and Baltic Sea region, while high geopotential is present over central Scandinavia and British Isles.

DISCUSSION

West Mediterranean

Another strong southerly jet streak enters the west Mediterranean. In the lee of the Atlas, a surface low pressure is expected over southwest Mediterranean, and low-level winds are expected to remain east in the relatively cool but moist boundary layer. This results in strong deep- and low-level vertical wind shear with 30-40 m/s 0-6 km shear, 7-12 m/s 0-1 km shear, and 100-400 J/kg 0-3 km storm relative helicity. Instability is likely, but strong capping inversion will be also present especially at the eastern flank of the jet streak. Near the Balearic Islands, capping will be weaker in the range of a frontal boundary and colder mid-levels. Chance for initiation is best underneath the cyclonic flank of the jet streak where some DCVA is forecast. Thunderstorms will likely organize and supercells are forecast to develop. Large hail and damaging wind gusts are expected with the stronger cells, and a few tornadoes are also not ruled out.

Eastern Mediterranean

Underneath the upper cut-off low, locally strong low-level buoyancy and weak vertical wind shear are present, and a few waterspouts are expected to form.