Storm Forecast
Valid: Tue 01 Jun 2010 06:00 to Wed 02 Jun 2010 06:00 UTC
Issued: Mon 31 May 2010 23:46
Forecaster: KOROSEC

A level 1 was issued for E Bulgaria, E Romania, Moldova and most of Ukraine into southern Belarus mainly for large hail, strong winds and tornadoes.

A level 1 was issued for northern Turkey mainly for very large hail and strong winds.

SYNOPSIS

An upper low, centered over northern Serbia in the morning hours, makes only slow progress northwards and reaches eastern Hungary by Wednesday morning. Ahead of this low, strong mid-level jet is placed over the eastern Balkans states. At surface, frontal system with strong cold/warm fronts serves as a focus for deep convection today. On the eastern flank of the building upper ridge over western Europe, a weak short-wave trough/disturbance crosses France in the afternoon hours. Slightly unstable airmass could result into some shallow electrified convection towards the evening hours.

DISCUSSION

.. E Bulgaria across E Romania towards Moldova ...

Rapid destabilization is expected to takes place ahead/along the well-defined cold frontal boundary, starting in the late morning hours. Backing LL flow with healthy boundary layer moisture ahead of the front will provide sufficient moisture and around 700-1000 J/kg of MLCAPE will release. Placed beneath the strong mid-level jet, moderate to strong deep-layer shear becomes favorable for organized severe storms. Given the more unidirectional wind profilers, linear mode convection/systems with bowing segments are likely. With SREH3 between 200 and 400 m^2/s^2, tornadic supercells can be possible as well, but mostly a well organized multicells and supercells with marginally large hail and damaging winds seem to be the primary threat.

... Ukraine and southern Belarus ...

Behind the surface warm front, a very rich boundary layer moisture advection takes place from the Black Sea region northwards across Ukraine into southern Belarus. Mixing ratios near 12-13 g/kg should easily result in strong instability, MLCAPE mostly around 1500-2000 J/kg or even higher values (mostly over south-central Ukraine) are quite likely. Only weakly capped warm sector doesn't seem to be holding convection for too long, so widespread initiation is expected towards the midday hours. Moderate shear which is holding closer to the upper low centre, is only partly overlaping with strong instability over Ukraine. But DLS of 15-20m/s and around 10m/s of 0-1km shear will still be in place. Additionally, with backing ESE-erly LL flow along the warm front, enhanced SREH above 300 m^2/s^2 and rather low LCL heights seem favorable for organized supercells. Threat for large large hail, strong winds and a few tornadoes will be possible. A high-end level 1 threat has been placed for these areas.

However, the central Ukraine will be closely monitored for a possible upgrade into level 2 if higher shear will be present to support more widespread and robust severe storms in the afternoon hours. Especially along and south of the northwards pushing warm front.

... Northern Turkey ...

Ahead of the weak surface low over SE Balkans, a level 1 was placed over the northern Turkey and southern Black Sea coastal areas where moderate instability releases with strong diurnal heating beneath the very steep mid-level lapse rates. With quite high LCL and instability overlaping with 15-20m/s of DLS, organized storms with very large hail/damaging winds threat will be possible.