Storm Forecast
Valid: Wed 06 2009 06:00 to Fri 06 2009 06:00 UTC
Issued: Sat 20 Jun 2009 21:38
Forecaster: DAHL

*** This forecast is valid from 21 June 2009 06:00 UTC until 22 June 2009 06:00 UTC ***

A level 1 was issued across the Ionian region and the western Balkans mainly for large hail and severe wind gusts.

A level 1 was issued across the W Ukraine mainly for excessive rainfall.

SYNOPSIS

Deep quasi-stationary upper long-wave trough is present over central portions of Europe, extending well into the central Mediterranean. At low levels, a weak and rather large-scale cyclonic circulation persists at the eastern periphery of the trough over the central Mediterranean into SE Europe. Some augmentation of the circulation beneath the DCVA regime at the SE extension of the trough is simulated early in the period. A weak high pressure area is slowly building eastwards from the eastern Atlantic/British Isles.

DISCUSSION

... central Italy ... central Ionian Sea ... W Balkans ...

Saturday's afternoon soundingss from the Mediterranean area indicate that some EML air was present over the southern Mediterranean, and indications are that this air will remain mostly over the southern portions of the Mediterranean on Sunday. This implies that lapse rates will remain rather weak over Italy and the Balkans. However, it does seem that boundary-layer moisture is rather robust over these regions, so that CAPE on the order of 1000 to 1500 J/kg could be realized.

A region of 25 m/s DLS is simulated over the Ionian Sea and the S Balkans late Sunday evening. However, this region seems to be somewhat south of the region of strongest upward forcing, also, the residual EML should result in stronger capping than farther north. Hence, confidence in widespread convection amidst the most favorably-sheared area is rather limited. Farther north, shear should generally be weaker, though GFS 12Z does simulate 15 to 20 m/s DLS.

Thinking is that rather widespread convection will exist in the vicinity of the DCVA-regime moving from the Tyrrheniaan Sea into the S Balkans during the day. Models suggest that the Adriatic region and the W Balkans will see most convection. Isolated large hail and severe wind gusts are to be expected. Also, excesssive rainfall may accompany the storms.

... Tyrrheniaan Sea ...

Beneath the upper thermal-low region over the central Mediterranean, scattered storms are expected. Coverage seems to be largest over the Tyrrhenian Sea late in the evening. LL buoyancy seems to become sufficient for strong miso-vortex stretching, so that a few waterspouts cannot be ruled out.

... W Ukraine ...

Convection will likely extend northwards along the E edge of the LL theta-e plume E of the large-scale upper trough. Over the W Ukraine, DLS is expected to exceed 20 m/s. The storms in this frontogenetic regime will likely tend to be elevated, which may limit their severe potential. However, convective rainfall exceeding severe criteria may occur. If the storms become SFC-based, an additional threat for large hail and damaging wind gusts exists.

... S Scandinavia ... N Germany .... Benelux ...

Showers and scattered thunderstorms should develop with diurnal heating in uncapped polar air across S Scandinavia, Germany, Benelux, and parts of Poland. Strong LL buoyancy suggests that potential for non-mesocyclonic funnel clouds/ tornadoes exists if miso-vortices are encountered by the convective cells. However, allover likelihood of tornadoes seems to be too low for a LVL1.

... S Iberia ...

Scattered thunderstorms may develop over the southern half of Iberia late in the day. Thermodynamic profiles should feature quite deep/dry CBLs so that downbursts may occcur. However, the models are not supporting the development of convection, so convective initiation could fail altogether. Will thus not issue severe probabilities at the moment.