Storm Forecast
Valid: Thu 12 Jul 2012 06:00 to Fri 13 Jul 2012 06:00 UTC
Issued: Wed 11 Jul 2012 22:43
Forecaster: GATZEN

A level 1 was issued for Moldova and suroundings mainly for excessive precipitation and large hail.

A level 1 was issued for the central Mediterranean and the central Balkans mainly for large hail.

A level 1 was issued for northern Italy and the northern Balkans mainly for large hail.

SYNOPSIS

With westerly mid-level winds, several vort-maxima travel across Europe into eastern Europe during the period. A cold front enters the Mediterranean, northern Balkans, and eastern Europe and continues to spread south-eastwards. Ahead of this cold front, a well-mixed air mass is situated over eastern Europe and the Mediterranean. Remaining low-level moisture overlapping with the lapse rates will be associated with CAPE values around 1000 J/kg across eastern Europe and south of the Alps.

DISCUSSION

Eastern Romania, Moldova, and surroundings

A mid-level short-wave trough travels eastward into the Black Sea region. A frontal boundary will move into Romania in the morning hours and thunderstorms will spread into the western part. Frontogenesis is expected in the wake of the mountains with convective initiation along the sea-breeze front or the cold front in the afternoon hours. Although deep layer vertical wind shear is rather weak, 0-3 km bulk shear will increase due to the frontogenesis to values of 15 m/s in the evening hours along the western Black Sea coast. Current thinking is that convection will grow upscale and merges into an MCS given the rather high cold pool potential. The slow movement due to possible back building and high moisture seem to increase the threat of excessive precipitation through-out the night, especially across Moldova and surroundings. Additionally, large hail and severe wind gusts are not ruled out.

Central Mediterranean and Balkans

An intense short-wave trough and 40 m/s mid-level jet streak will rapidly travel across the central Mediterranean during the period. It will provide strong QG forcing leading to a weaker capping inversion. Although convective initiation is questionable, the strong synoptic forcing is expected to lead to thunderstorms that initiate over the land masses. These storms will rapidly organize given 20 m/s 0-6 km bulk shear. Large or very large hail is expected with these storms that will move eastward quickly and eventually decay offshore. Convective activity will spread into the Balkans during the afternoon and evening. Severe wind gusts and tornadoes are not ruled out with these supercells as well.

Northern Italy and surroundings

In the wake of the Alps, warm and unstable air masses will remain on Thursday. QG forcing is expected at the right entry region of a intense jet streak across Germany. A surface convergence is expected and storms will likely initiate given weak convective inhibition. Storms are forecast to organize in the 20 m/s DLS regime. Multicells and supercells are forecast. Large or very large hail will be the main threat, but a tornado is not ruled out. Storms will decay in the evening hours given decreasing forcing and dry westerly low-level winds.

Eastern Europe

Ahead of the frontal boundary, an unstable air mass with CAPE in the order of 1000 J/kg is forecast. Given weak vertical wind shear, most storms will be unorganized. However, stronger pulse storms may be associated with large hail and excessive precipitation.

Northern Germany and Poland

Near the base of the polar trough, an unstable air mass and strong QG forcing are forecast to support thunderstorms. Isolated large hail is not ruled out with stronger storms.