Storm Forecast
Valid: Mon 18 Jun 2012 06:00 to Tue 19 Jun 2012 06:00 UTC
Issued: Sun 17 Jun 2012 22:24
Forecaster: SCHLENCZEK
A level 2 was issued for central/ eastern Germany and W Poland mainly for large/ very large hail, severe wind gusts and tornadoes.
A level 1 surrounds the level 2 for large hail, severe wind gusts and tornadoes.
A level 1 was issued for N Italy mainly for large hail and severe wind gusts.
A level 1 was issued for the region of the northern Carpathian Mountains mainly for large hail and severe wind gusts and to a lesser extent for excessive precipitation.
A level 1 was issued for the region of the N Dinaric Mountains mainly for large hail, severe wind gusts and excessive precipitation.
A level 1 was issued for E Ukraine mainly for large hail, excessive precipitation and severe wind gusts.
SYNOPSIS
A westerly jet streak meanders over western and also eastern Europe with two shortwave troughs embedded in this structure. One of them should be located over the British Channel on Monday morning and will move towards the Baltics. Ahead of this trough, hot and unstable air is advected into most parts of central Europe, leading to MLCAPE in order of 1 - 2 kJ/kg.
The second trough is associated with a deepening cyclonic vortex over S Finland and tends to move eastwards. In the late afternoon hours, a new shortwave trough affects the N Maghreb States and S Iberia.
DISCUSSION
...Iberia, France...
Along the cold front of the low pressure complex, strong upper level winds lead to 20 - 25 m/s of 0-6 km bulk shear and some low-end instability. Embedded vorticity maxima may provide enough lift for convective initiation and storms in such an environment may produce isolated large hail and severe wind gusts. An isolated tornado cannot be discounted either. As most of the instability is tied to the boundary layer, thunderstorm activity will gradually decrease after sunset.
...Germany, Czech Rep. and Poland...
Moderate instability will build up ahead of a shortwave trough, starting in the late morning hours over W Benelux and SW Germany. Due to the jet streak near the trough, some 15 - 25 m/s of 0-6 km deep layer shear overlap with instability. The main question is where the chance for initiation of organized multicellular and supercellular convection is most likely. Some 15 - 20 m/s at lower levels may likely support intense downdrafts and 150 - 350 mē/sē SRH3 should favor organized multicellular lines and supercells. Any isolated storm in this environment will pose a risk of large to very large hail, severe wind gusts and also a possible tornado. Excessive convective rainfall may be expected only locally as storms will move quite fast with approx. 20 m/s. Some high resolution models like the 4 km WRF suggest the formation of a squall line over NE Germany which will then move into Poland. In this case, there will be a high probability of severe to very severe wind gusts.
Further upstream and downstream of the LVL2 area, less instability and/ or forcing are expected and therefore a lower probability of severe weather is anticipated.
...N Maghreb States...
Some 500 - 1000 J/kg MLCAPE - locally more - and 20 m/s of deep layer shear will provide favorable conditions for organized multicellular storms and also a few supercells as SRH3 is also enhanced. The main threat should be large hail and severe wind gusts.
...Other LVL1 areas...
A marginal LVL1 was issued also for N Italy, the N Dinaric Mountains, the N Carpathian Mountains and E Ukraine as moderate to high instability should be in place with rather weak shear. A few large hail/ severe wind gust events may occur with the strongest storms. As storms will tend to move slowly, local excessive precipitation cannot be ruled out either.
