Storm Forecast
Valid: Sun 26 Jul 2009 06:00 to Mon 27 Jul 2009 06:00 UTC
Issued: Sun 26 Jul 2009 05:30
Forecaster: SCHLENCZEK
A level 1 was issued for eastern parts of Ukraine and SW Russia mainly for severe gusts, large hail and excessive precipitation.
A level 1 was issued for W Russia and E Belarus mainly for excessive precipitation and severe gusts.
SYNOPSIS
An upper trough centered over the Baltic Sea is forecast to shift eastward during the period, affecting W / NW Russia. At its eastern flank, cyclogenesis is expected over E Ukraine in the vicinity of a well-defined frontal boundary. The developing surface low will affect NE Ukraine and SW Russia on Sunday afternoon / evening.
Another upper trough is present over Scotland / N Ireland, leading to a strong southwesterly flow at its southeastern flank. A very hot airmass is advected into parts of Spain and later on also into S France. LL moisture advection will lead to some low-end instability in this strongly capped airmass. 00 UTC Soundings from LXGB and LEMD show a well-defined EML which should also be present over SW France on Monday morning.
DISCUSSION
...NE Spain, S France...
It is questionable whether initiation will occur or not in a hot and strongly capped airmass which is advected northeastward from Morocco / S Spain. GFS does not show any precipitation signals and WRF does the same. Kinematics are quite good for severe thunderstorms, given 20 m/s deep layer shear and 200 - 300 mē/sē SRH3. If an isolated storm develops it will probably become supercellular, capable of producing large hail and damaging gusts. At this moment, confidence is too low that initiation will occur and no general thunderstorm area / threat level is issued. This region has to be monitored for a possible update.
...E Ukraine, SW / W Russia, E Belarus...
A tongue of very warm and moist air ahead of the upper trough is advected into E Ukraine and SW Russia, leading to about 1 kJ/kg MLCAPE which may be locally enhanced. Satellite images show an old MCS over the SW Black Sea which may re-develop in the late morning / early afternoon. As the upper flow is almost parallel to the cold front, a long line of briefly organized multicells and maybe also some supercells is expected to develop which may produce excessive rainfall as main threat. Large hail and severe wind gusts are also possible with the more discrete storms. Later on, storms will also move into the eastern parts of Belarus where GFS predicts convective rainfall in excess of 100mm / 12 h.
...S Finland, Baltic States, E Poland, W Belarus...
In the wake of the trough, diurnal heating will lead to some hundred J/kg of SBCAPE and showers / thunderstorms are forecast in a weakly sheared environment. Those singlecell storms / briefly organized multicells may pose a threat of marginally severe hail and gusty winds.
