Storm Forecast
Valid: Thu 27 Jun 2013 06:00 to Fri 28 Jun 2013 06:00 UTC
Issued: Thu 27 Jun 2013 08:37
Forecaster: PUCIK
A level 2 was issued for NE Romania, Moldovia and South - Central Ukraine mainly for large hail, severe wind gusts, excessive precipitation and tornadoes.
A level 1 was issued for a belt from NW Greece towards N Ukraine mainly for large hail, severe wind gusts and excessive precipitation.
A level 1 was issued for NW Russia and Finland mainly for large hail, excesssive precipitation and severe wind gusts.
A level 1 was issued for NW Italy mainly for large hail and excessive precipitation.
SYNOPSIS
A large cyclonic vortex at mid to upper troposphere centered over N Germany / Denmark is expected to remain quasi stationary during the forecast period with the most active areas regarding DMC activity expected on the southern and especially eastern flank of the low. Subtle short-wave troughs are expected to rotate around the vortex, one crossing Italy and other one streaming from Romania towards Ukraine. Closer to the surface, center of the low will shift towards the Northern Sea, while a wavy frontal system will run from E Romania towards Ukraine, Belarus and then curve towards Scandinavia.
DISCUSSION
... W Greece, Bulgaria, E Romania, Moldova, Central Ukraine ...
Ahead of the wavy frontal boundary, surface observations show moist low-levels with dewpoints mostly in the upper teens. Moderately steep mid-level lapse rates have been sampled by 00 UTC Odessa sounding and in such setup, moderate CAPE values between 500 and 1500 J/kg seem plausible, increasing towards the north. Rather low LFC levels, along with surface convergence with ensuing sea breeze and passage of the short-wave trough aloft should provide plenty of opportunities for convective initiation. 15 to 20 m/s of DLS thanks to the presence of enhanced mid level flow aloft and locally over 200 m2/s2 of SREH 0-3km over NE Romania and Central Ukraine thanks to the backing low level flow point towards the possibility of well organised convection, including supercells. Primary threats should be large hail and severe wind gusts, especially in case of supercells. Towards the evening, clustering into one or two MCS might also promote excessive rainfall threat in case that parallel stratiform form evolves or severe wind gusts in case that forward propagating linear system ensues. Moreover, strengthening of LLS towards the evening over N Romania and Central Ukraine, in conjunction with the reduction of LCL heights might actually favour one or two tornadoes especially in case that convection stays in isolated form. In the region where all of these severe threats will be possible, a Level 2 is introduced.
... NW Russia, Finland ...
A very war and humid airmass has advected over the region as evidenced by morning observations with dewpoints exceeding 20°C at many places. Despite rather weak vertical wind shear, moderate to high CAPE values along with steep mid-level lapse rates - this evidenced by Petrozavodsk 00 UTC sounding with more than 2500 J/kg of MLCAPE. In such conditions, stronger multicells might be capable of large hail and severe wind gusts with an isolated excessive precipitation event possible given weak storm motion and possible clustering into large multicells or ill-organised MCS.
... NW Italy ...
Moderate degree of latent instability is forecast by both ECMWF and GFS over the region with 10 to 15 m/s of DLS available, possibly locally slightly enhanced by the topographic influence of the Alpine range. Widespread storms are forecast to form thanks to the approaching short-wave trough with stronger multicells capable of large hail and excessive precipitation.
