Storm Forecast
Valid: Mon 08 Aug 2016 06:00 to Tue 09 Aug 2016 06:00 UTC
Issued: Mon 08 Aug 2016 03:11
Forecaster: VAN DER VELDE
A level 2 was issued for NW Russia mainly for severe convective wind gusts, tornadoes and large hail.
A level 2 was issued for E Ukraine and W Russia mainly for large hail.
A level 1 was issued for S Balkan mainly for excessive convective precipitation and large hail.
A level 1 was issued for N/W Poland mainly for isolated tornado and severe convective wind gust chances.
SYNOPSIS
The European synoptic situation is characterized by a large low centered near Norway with sharp pressure gradients, the Azores High extension over southwestern Europe, the old Italian low now destabilizing the southern Balkan, and a vigorous low over northwestern Russia. The latter features a well-defined cold front and occlusion front wrapped around, with unstable airmass in the warm sector combined with stroong low-level shear. The Norwegian low pushes two cold fronts into western/central Europe. The first cold front with slightly unstable air (200-500 J/kg MLCAPE) between E France and N Poland lacks dynamic lifting. Some WRF models hardly predict precipitation on it. The second cold front follows a few hundred km behind, but will be associated only with a shallow convective line at best., with poor mid level lapse rates.
DISCUSSION
...NW Russia...
The main focus is the fast cold front near the center of the low where 1000-2000 J/kg MLCAPE is removed. Shear vectors cross under a steep angle with the front, supporting solid multicell systems with organized severe wind gust threat, including bow echoes with support from 10-15 m/s 0-1 km shear, which also favors tornadogenesis in the more isolated or embedded supercells. Large hail is also likely. Further west, along the occlusion more stationary storms can produce intense/excessive convective rainfall. Activity will start early in the day.
...E Ukraine/W Russia...
As a mid level trough moves into this region and at low levels a wave in the front develops, convective initiation is likely and under the influence of 15 m/s deep layer shear, 1000 J/kg MLCAPE and 2000 m cloud bases, multicell and supercell storms can develop large hail and severe wind gusts.
...Albania, Macedonia, Greece region...
Weak storm motion but persistent lifting and weak capping should stimulate excessive precipitation sums. To the south and east over Greece and NW Turkey, a mid/upper level wind maximum creates large wind shear across the N Aegean area, and NW Turkey (300 mē/sē SREH and 1000 J/kg MLCAPE in GFS) but initiation will be difficult due to a cap. However in the fringes of the good shear zone near Bulgaria capping will be weak, cloud bases higher and formation of supercells producing large hail may be possible.
...Poland...
Overlap of the weak CAPE zone with 15 m/s 0-6 km shear could allow more dynamical cells which with a slighly enhanced 0-1 km shear (8 m/s) might allow a tornado event. But some models hardly produce any convective signals along the cold front so the confidence for storms is not large.
