Storm Forecast
Valid: Wed 09 Aug 2006 06:00 to Thu 10 Aug 2006 06:00 UTC
Issued: Wed 09 Aug 2006 04:34
Forecaster: GATZEN

SYNOPSIS

Amplified upper trough present over Europe. At its southern flank ... strong upper jet streak affects northern Africa and central/eastern Mediterranean Sea. At lower levels ... very warm subtropic airmass has left most of the forecast region. Rather cool airmass has spread into most of Mediterranean ... where warm sea surface has lead to steep lapse rates and quite rich low level moisture ... yielding CAPE in the order od 1000 J/kg. To the northwest ... cool maritime airmass advects into northwestern Europe.

DISCUSSION

Northern Africa, southern Mediterranean

Broad surface low pressure has formed south of the Atlas mountains in the range of hot desert airmass. To the north ... easterly surface winds advect moist airmass originating from the Mediterranean into Atlas mountains. Latest model output shows a tongue of dewpoints >10°C south of the Atlas mountains and rather strong easterly surface winds. Given EML above the boundary layer ... GFS CAPE forecast of 500...800 J/kg seems to be reasonable. Thunderstorms have already formed over northern Africa during the night hours. Today ... diurnal heating and upslope flow should lead to initiation over the Atlas mountains and thunderstorms that form should move eastwards. While strong vertical wind shear will be present mostly south of the forecast region ... greatest potential for severe convection should exist over northern Tunisia ... where a few mesocyclones or multicells are expected ... capable of producing large hail and severe wind gusts. Chance for tornadoes will be slightly enhanced given strong LLS. Thunderstorms should move into southern Mediterranean during the period.

Central Mediterranean

Axis of quite intense short-wave trough is expected over western-central Mediterranean today. To the east ... strong upper jet streak affects central Mediterranean. At low levels ... a weak low pressure system is expected to move from Sardinia to southern Adriatic. In the range and east of this low ... southerly to easterly surface winds are expected ... and latest soundings show quite rich boundary-layer moisture and steep low-level lapse rates. Thunderstorms have already formed and should go on during the whole period ... spreading into Italy and Adriatic region. Given strong DLS especially from southern Italy to southern Adriatic and moderate DLS further north ... thunderstorms should organize and merge into a few MCS ... capable of producing severe wind gusts and intense precipitation. Embedded mesocyclones may lead to large hail especially in the southern parts. Given low-level CAPE and at least enhanced LLS ... chance for tornadoes is slightly enhanced over most of the region.