Storm Forecast
Valid: Wed 19 Mar 2008 06:00 to Thu 20 Mar 2008 06:00 UTC
Issued: Tue 18 Mar 2008 22:56
Forecaster: GATZEN

SYNOPSIS

Well-developed arctic trough is present over Scandinavia, while polar frontal zone forms an amplified long-wave trough that covers most of Europe. Axis of low geopotential stretches into south-western Europe, where the eastern flank of Atlantic omega high is present. A strong upper westerly jet is expected across the Mediterranean during the period. At low levels, cold polar/arctic air mass has flooded most of Europe. This cold air mass is quite stable. Steep mid-level lapse rates are expected in the range of the main trough axis over eastern Germany/Poland/Belarus, and given some low-level moisture and enough daytime heating to overcome the cap, showers and some thunderstorms are forecast. Given weak vertical wind shear and instability, strong thunderstorms are not forecast. Soft hail and strong wind gusts are expected to be the most significant threat.

Over southern Iberian Peninsula, a cut-off is forecast to form during the period. Some thunderstorms are expected to concentrate in the range of the trough center, where weak vertical wind shear is likely. To the east, some instability will be present over Balearic region given steep low- to mid-level lapse rates and dome low-level moisture. However, it seems that synoptic scale lift will be very weak in the range of the cut-off. Best potential for a few storms is forecast underneath the trough axis, but sever thunderstorms are not forecast given weak forcing and low-level convergence.

DISCUSSION

Eastern Aegean, western Greece

A strong upper westerly flow with several waves is traveling over the Mediterranean. At lower levels, an intense frontal boundary has developed over north Mediterranean. Along the quasi-stationary boundary, weak cyclogenesis is expected by latest model output. To the south of the main low-level convergence, quite strong southerly winds are forecast to develop especially over Aegean, advecting moist and rather warm air mass northward. This air mass is expected to be characterized by steep mid-level lapse rates as already indicated by latest ascends, and latest GFS CAPE calculation seems to be quite reasonable. Showers and thunderstorms may form embedded in stratiform rain along the frontal boundary. Given strong vertial wind shear, some well-developed multicells like bowing lines and mesocyclones are forecast, capable of producing isolated large hail and severe wind gusts. Convective activity is forecast to spread into Turkey late in the period.