Storm Forecast
Valid: Mon 22 Nov 2010 06:00 to Tue 23 Nov 2010 06:00 UTC
Issued: Mon 22 Nov 2010 01:14
Forecaster: DAHL

A level 2 was issued across the Ionian Sea and the southwestern Balkan States, mainly for severe wind gusts, tornadoes, large hail, and excessive convective precipitation.

A level 1 was issued across the Ionian Sea ... parts of southern Italy ... the Adriatic Sea ... the southwestern Balkans ... and the Aegean regions mainly for severe wind gusts, tornadoes, large hail, and excessive convective rain.

... SYNOPSIS ...

On Sunday evening ... a deep large-scale upper trough was located over western Europe, extending well into the western Mediterranean Sea. This feature will make some eastward progress on Monday, with its eastern periphery reaching the Balkan States late in the day. Ahead of this trough, an elongated SFC low is maintained, which will develop two separate centers, the northern of which is expected to undergo substantial deepening over the Poland/Czech-Republic/Germany-area on Monday. A plume of warm and moist air is advected across the Mediterranean into eastern Europe ahead of this system.


... DISCUSSION ...

... Ionian/Adriatic and Aegean regions ...

It seems that the air mass ahead of the cold front associated with the large-scale upper trough will become increasingly unstable during the period, owing to a combination of strengthening low-level moisture and steepening lapse rates. In addition, 20 to 30 m/s DLS will overspread this air mass. This suggests that the thunderstorm activity along and ahead of the cold front should gradually increase early on Monday.

The strong shear suggests that well-organized multicells/line segments as well as mesocyclones will be possible. The main threats with this activity should be severe wind gusts and possibly some hail. Especially over the Ionian Sea and the western coastal regions of the S Balkans, low-level shear should be maximized (> 15 m/s) which could result in a couple of tornadoes.
In addition to these threats ... continuous redevelopment of deep convection amidst the upslope flow regime over the W Balkans may support excessive convective precipitation.

... western Mediterranean ...

In the wake of the front over the western portions of the Mediterranean, cellular convection should persist. Steep low-level lapse rates and rather decent low-level shear could promote an isolated tornado or two, but given minimal deep shear, it seems that the overall severe threat is rather low.