Storm Forecast
Valid: Thu 20 May 2010 06:00 to Fri 21 May 2010 06:00 UTC
Issued: Wed 19 May 2010 21:55
Forecaster: GATZEN

A level 1 was issued for Greece and the Aegean mainly for large hail.

SYNOPSIS

The intense and unseasonably cool trough over Central Europe moves south-eastward into the Mediterranean. Along the southern periphery of the trough, a strong mid-level jet propagates over the south-east Mediterranean. While a high is present over western Europe the low-level cold air advection over the central portions goes on. A tongue of moist low-level air is present from Sweden to Poland and Ukraine.

DISCUSSION

Greece and Aegean region, southern Turkey

A rather cool air mass is present over the Mediterranean Sea. Latest soundings indicate well-mixed low levels and some boundary-layer moisture, resulting in weak instability. This air is forecast to spread into Greece during the period with westerly winds in the range of a trough axis. While a frontal wave will build underneath the southern portions of this trough, some warm air advection will be present as well as strong DCVA in the range of the jet streak, and lift is forecast to lead to increasing instability in the afternoon hours.

Deep moist convection is expected to initiate, mainly across the land due to diurnal heating. Storms that form will likely organize given the strong deep layer vertical wind shear. While multicells are forecast to be the main convective mode, supercells may form ahead of a low-level convergence that develops underneath the trough axis, where backed low-level winds will result in increasing hodographs (around 150 m²/s² SRH in the lowest 3 km). Given the favourably low-level buoyancy and locally 7-10 m/s low-level vertical wind shear, tornadoes are not ruled out with isolated supercells. Isolated large hail seems to be the most significant threat over the affected region, though. While the trough axis moves on, showers and thunderstorms will reach Turkey. Due to upslope flow, excessive rain cannot be ruled out.