Storm Forecast
Valid: Tue 08 Apr 2008 06:00 to Wed 09 Apr 2008 06:00 UTC
Issued: Tue 08 Apr 2008 06:02
Forecaster: GATZEN

SYNOPSIS

Widespread low geopotential is present over eastern Atlantic and western Europe. A broad but rather large temperature gradient is present over all of southern Europe during the period. In mid-levels, a strong westerly flow is present, as upper jet streak curving around the eastern Atlantic trough axis will enter south-western Europe, spreading across the Mediterranean during the period.

DISCUSSION

Most of the Mediterranean

Warm mid-level air mass is present over most of the Mediterranean during the period. This air mass is well-mixed as indicated by latest ascends. Given rather cold boundary layer over the cool sea surface, only weak CAPE may develop during the day in the range of a short-wave trough moving across north Mediterranean today. Convection that may develop is not expected to profit from deep-layer vertical wind shear given rather warm mid-levels and therefore quite shallow convection, and organized thunderstorms are not likely.

South-western Iberian Peninsula

Moist boundary-layer is forecast to spread into the region south of the main frontal zone. Aloft, warm air mass may lead to a significant capping inversion. During the period, strong upper jet streak will likely lead to strong QG forcing, and embedded frontal systems will also be focus of lift that may be strong enough to initiate thunderstorms. Although most convection will be embedded in stratiform rain, strong vertical wind shear is also forecast as well as favorably veering profiles in the warm air advection regime. Thunderstorms that form in regions with positive low-level buoyancy may evolve mesocyclones, chance for such development is very unlikely, though, and a categorical risk level is not issued. An isolated tornado is not ruled out given strong low-level vertical wind shear and SRH.

Northern Tunisia region

Ahead of the propagating jet streak, a short-wave trough moves eastward over west Mediterranean, leading to some QG forcing in the range of the well-developed warm front/frontal wave over northern Africa. Although convective inhibition may be quite large over most of the period, diurnal heating and some lift over the mountains may be sufficient for initiation of isolated thunderstorms. They will likely profit from strong vertical wind shear and favorably veering profiles. Supercells are not ruled out capable of producing isolated large hail in the afternoon hours. Convection will rapidly die after sunset.