Storm Forecast
Valid: Mon 15 Sep 2008 09:00 to Tue 16 Sep 2008 06:00 UTC
Issued: Mon 15 Sep 2008 09:09
Forecaster: GROENEMEIJER

SYNOPSIS

A high-over-low blocking parttern persists across Europe, with the high over northern Finland and the low moving east from the Alps to Hungary. On the eastern flank of the low, warm and unstable air over the eastern Mediterranean, the Aegean Sea is advected northeastward into the Black Sea basin. West of the low, drier and colder air overspreads the western and central Mediterranean.

DISCUSSION

...Western Balkans from Bosnia to the Peloponnesos...

A surface low has developed across the southern Adriatic Sea. A cold front that stretches southward from Albania across the Ionian Sea moves eastward. Ahead of the front, up to 2000 J/kg of MLCAPE is present and about 20 m/s 0-6 km deep-layer shear. Strongly clustered convective activity is ongoing near the front, intenisified by an upper-level trough that moves eastward from the Adriatic during the forecast period. Shear supports a few embedded supercells capable of producing large hail, and damaging winds. An isolated tornado cannot be excluded either. Flash flood threat across the area will be substantial, due to the back-building nature of the storms. During the afternoon, the front moves inland and the activity in western Greece should subside.

As the cold front and reaches central Greece, influx of warm moist air from the Aegean Sea will become available to the front. This will likely result in the re-intensification of the convective activity across northern Greece, and southern Bulgaria.

...Eastern Balkans, from Bulgaria through Moldova, and the SW Ukraine...

Clustered convective activity should spread into northern and eastern Bulgaria and eastern Romania during the evening an night, before moving into Moldova and Romania. A large part of the activity will probably be elevated, but near the Black Sea coast, surface-based convection is possible as well. Per numerical models low-level shear and storm-relative helicity should gradually increase. As a result, an ongoing severe threat is forecast. Besides large hail and damaging gusts, some tornado threat will also be present, most likely near the Black Sea coast. The forecast deep-layer shear is only moderate, 15 m/s. This fact, and the question whether convection will actually be surface-based preculde the issuance of a higher threat level at the moment.