Storm Forecast
Valid: Tue 26 Jul 2011 06:00 to Wed 27 Jul 2011 06:00 UTC
Issued: Mon 25 Jul 2011 22:40
Forecaster: KOROSEC

A level 2 was issued for eastern Romania, Moldova, central Ukraine and parts of southern Belarus mainly for large to very large hail, damaging winds and intense rainfall.

A level 1 was issued for surrounding areas of level 2 across the ESE Balkans towards the Baltic States as well as for parts of western Balkan Peninsula mainly for large hail, damaging winds and locally excessive rainfall.

A level 1 was issued for parts of western Russia mainly for large hail and strong winds.

A level 1 was issued for extreme south France and NE Iberia mainly for isolated large hail and strong wind gusts.

SYNOPSIS

A large upper trough/low finally starts to vanish over much of central Europe as mid levels are warming up. Still, several upper level disturbances are embedded around it. Hot and humid subtropical airmass continues to advect across eastern Balkans northwards, making unsettled conditions on Tuesday. At surface, a shalow low moves over eastern Balkans with a focus of convective activity along its front. Another front travels across S France/NE Iberia during the second half of the forecast period.

DISCUSSION

... eastern Romania, Moldova, central Ukraine and parts of southern Belarus ...

Another day of rather robust convective activity is expected across ESE Balkans as BL airmass is strongly unstable with SFC dewpoints around 20s. Pre-frontal SE flow will maintain high LL mixing ratio values during the day while well defined EML overspreads the region. Resulting in high instability, MLCAPE values of around 1500 to more than 2000 J/kg seem reasonable to become available. With strong SFC heating, moderate capping should be eroded by early afternoon and rather widespread storm initiation is expected along the local complex topography as well as along the several old outflow boundaries from the previous night activity. 10-15 m/s of deep layer shear will still be available, mostly well overlaping with instability, so organized severe storms (multicells and supercells) with threat for large to very large hail, strong damaging winds and excessive rainfall seem likely to take place. With very limited LL wind shear, tornadoes are unlikely to form, but cannot be completely ruled out with interacting cells with each other and/or with complex topography, enhancing LL SREH locally. Storms will tend to cluster into one or two MCSes and activity should continue into the early night hours as LLJ from the Black Sea maintains the instability.

Areas surrouding the level 2 should see the convective activity mostly aligned to the daytime hours. Still, 700-1200 J/kg will be locally available over the Balkans and towards the Baltic states as well as at least around 10 m/s shear. Expect some organized storms, but activity will be more isolated over these areas and could as well produce some large hail and strong wind events.

A small level 1 was also placed for parts of western Balkans mostly over Bosnia and W Serbia as ML disturbance crosses the region in the afternoon hours, when some instability will become available at peak heating hours. Decent forcing seem to be enough for storm initiation in mid afternoon where wind profiles will be supportive of a few organized storms, capable of producing some larger hail and strong winds.

... parts of western Russia ...

A threat level 1 was placed over Northern Hills region where moderate instability overlaps with around 15 m/s of deep layer shear and could support organized severe storms if storms manage to fire. A weak disturbance crosses the region in the peak heating hours, where rather hot mid levels should be holding strong cap, but some isolated activity is likely to occur. Some large hail/damaging winds events will be possible.

... NE Iberia into S France ...

Another disturbance/short-wave trough is forecast to cross these areas in the afternoon/evening hours from the NW. Near SFC flow will advect high moisture inland into NE Spain where convergence is clearly evident. With UL support and enough QG forcing, isolated storms should fire in the afternoon hours and continue into the evening/early night hours, spreading into the western Mediterranean sea. With rather limited instability, some uncertainities exist for how intense the storms will be in the afternoon hours. But with moderate 15-20 m/s deep layer shear in place, storms should easily organize and support some large hail and strong winds if enough instability becomes available. Models suggest that a small cluster is possible overnight towards the open seas.

The rest of highlighted area around the Alps, central Italy as well as Scandinavia will mostly face the daytime driven convective activity with only very low wind shear, so organized storms are less likely to occur. Activity will diminish after sunset as instability vanishes.