Storm Forecast
Valid: Wed 12 Jun 2013 06:00 to Thu 13 Jun 2013 06:00 UTC
Issued: Tue 11 Jun 2013 23:11
Forecaster: PUCIK

A level 1 was issued for a belt spanning from Greece towards Romania mainly for excessive precipitation and to the lesser degree for large hail.

A level 1 was issued for Turkey mainly for large hail.

SYNOPSIS

Over eastern part of Europe, a large trough is beggining to fill, slowly moving eastwards and is expected to start a cut-off process with center remaining over Northern Turkey. A ridge is expected to amplify from Iberia towards Central Europe during the day, with strong mid to upper tropospheric jet observed on its northwestern flank as the trough from Atlantic begins approaching Western Europe. Closer to the surface, a deep low pressure system is forecast to affect British Isles, while a diffuse frontal boundary is forecast to persist over Eastern Europe.

Thunderstorm activity will be dominant again especially over southeastern part of the continent with moist low levels (e.g. Eastern Romania / Bulgaria with dewpoint observations over 16°C) and rather cold temperatures aloft. Nevertheless, weakening trough will likely limit potential for strong deep layer wind shear, so no significant threat of (extremely) severe convection is forecast for this day.

DISCUSSION

... Greece, Bulgaria, Romania, Moldova to Ukraine ...

With very moist easterly to northeasterly flow at low-levels and only weak mid to upper tropospheric flow, we expect slowly moving thunderstorms with rather low LCLs, easily anchoring their re-development on the local convergence zones or to the topographic features. Thanks to the high effective PW values and also high relative humidity in the significant portion of troposphere - especially in the areas which already experienced convective activity before, an excessive precipitation threat will likely be elevated. The highest threat should be confined to the areas with rich terrain. As we move towards Ukraine, CAPE values should increase with steeper mid-level lapse rates and also vertical wind shear should be a bit more pronounced. Here, large hail threat will be higher than for the rest of the area. With some discrepancies between the NWP output regarding the exact thunderstorm and highest threat location, we go with a rather broad Lvl 1 for this setup.

... Turkey ...

Not much vertical wind shear is forecast as the trough decays, but still, especially southern extents of the Lvl 1 might see DLS values exceeding 15 m/s. Combining this with the rather cold temperatures at mid-troposphere and quite steep lapse rates in the hail growth layer, we would not rule out a well organised multicell capable of large hail in this region as the moist low level flow from the Black / Aegean Sea contributes to moderate latent instability.