Storm Forecast
Valid: Sun 31 Jul 2011 06:00 to Mon 01 Aug 2011 06:00 UTC
Issued: Sat 30 Jul 2011 21:08
Forecaster: SCHLENCZEK
A level 1 was issued for E Spain for large hail and severe wind gusts.
A level 1 was issued for the N Adriatic region and N Dinaric Mountains / W Balkans for excessive precipitation and large hail.
A level 1 was issued for parts of Poland, Belarus, W Ukraine and the Baltics for large hail and excessive precipitation.
A level 1 was issued for central / E Ukraine and W Russia for large hail, severe wind gusts and excessive precipitation.
SYNOPSIS
Between a high pressure system over northern Scandinavia and Greenland and another upper high over the Azores and the E Mediterranean, numerous disturbances are found. One small upper low SW of Iberia moves towards Iberia and may lead to severe convection when it reaches Spain on Monday afternoon. Another relatively strong upper low is located near Iceland and affects Ireland and UK. The most important low pressure system associated with severe weather should be the large but rather flat trough over Russia and Ukraine. An airmass with moderate instability overspreads large portions of eastern Europe but there are only a few regions where some 10 - 15 m/s of deep layer shear overlap with regions of 1 - 1.5 kJ/kg MLCAPE. The main threat on Sunday will be marginally severe hail and local flooding / severe wind gusts in a moderate CAPE / low shear environment over E Europe. Low level shear and 0-1 km SRH as well as 0-3 km MLCAPE are very low in entire Europe and therefore tornadoes are unlikely.
DISCUSSION
...S Norway and Sweden...
MLCAPE in order of 500 J/kg is forecast for the southern parts of Scandinavia and thunderstorms are likely to evolve in a weakly sheared environment. Some of them may produce an isolated marginally severe hail event and / or some local flooding due to the low storm motion but a threat level is not warranted.
...Poland and Baltics towards Ukraine and W Russia...
A broad region with locally > 1.5 kJ/kg MLCAPE is found over eastern Europe. Instability should be maximised over NE Poland as well as W Russia and E Ukraine. 0-6 km shear is strongest over Ukraine and regions further east (which are not included in the forecast area) and conditions for severe thunderstorms increase towards the east. A steep vertical gradient of Theta-E increases the chance for severe wind gusts over the eastern parts of the forecast area. Further west, isolated large hail and local flooding should be the primary threat.
...E Spain...
Some few hundred J/kg CAPE should be created by diurnal heating and may lead to some isolated to scattered thunderstorms which develop in an environment with approx. 15 m/s of 0-6 km deep layer shear. Like on Saturday, multicells and isolated supercells should be the dominant convective mode and may pose a risk of marginally severe hail, severe wind gusts and local flooding due to heavy rainfall.
...Italy, Adriatic, W Balkans...
Low to moderate instability will be created during the day over Italy and the regions along the Dinaric Mountains towards W Balkans which will lead to scattered thunderstorms in a weakly sheared environment. Given quite high amounts of effective precipitable water and a continuous westerly flow, heavy rainfall and excessive precipitation may occur over the mountaneous area of Slovenia, Croatia, Bosnia and Serbia as slow moving and / or back building multicells are likely to develop. An isolated large hail event is not ruled out either.
...NW Turkey...
Models show some low-end instability overlapping with 25 - 30 m/s of 0-6 km deep layer shear over NW and N Turkey, but high CIN should preclude convective initiation. Even though GFS does not predict any precipitation for this region, an isolated severe storm with large hail / severe wind gusts cannot be ruled out.
