Storm Forecast
Valid: Wed 25 Jul 2012 06:00 to Thu 26 Jul 2012 06:00 UTC
Issued: Tue 24 Jul 2012 21:01
Forecaster: SCHLENCZEK
A level 2 was issued for the E Alpine region mainly for excessive convective precipitation, large hail and severe wind gusts.
A level 1 was issued for parts of central and SE Europe mainly for excessive convective precipitation, isolated large hail and severe wind gusts.
A level 1 was issued for N Morocco and Algeria for isolated large hail and severe wind gusts.
SYNOPSIS
A low pressure system resides over the N Adriatic. Ahead of this low, a hot and unstable airmass is advected into most parts of central and SE Europe. As the background flow is rather weak, storm motion is relatively slow.
Another low pressure system is present over the Arctic Ocean and affects Scandinavia, Finland and NW Russia. Some isolated thunder is possible in an environment with moderate 0-3 km shear and low-end instability.
DISCUSSION
...E Austria, Hungary, S Czech / SW Slovak Rep., SW Romania, N Serbia...
Hot and moist air is advected into the region of interest by a low pressure system centered over the N Adriatic. Instability will increase during the day and MLCAPEs in order of 1 kJ/kg and more should become available in most parts of SE Europe, combined with some 10 - 15 m/s of 0-6 km bulk shear in the eastern part of the LVL2 area. Strong LL moisture advection leads to high values of effective PWAT (locally 30 - 50 mm) in an environment with weak winds at the lower levels. It is likely that most of the multicell storms in this area will move very slowly or tend to propagate upstream, which increases the chance of excessive precipitation and flash floods. Apart from the heavy rainfall risk, some storms may produce large hail and severe wind gusts as well. As the LL flow is very weak in most places and the cloud base is only a few hundred meters AGL, an isolated tornado cannot be ruled out either.
In the western parts of the LVL2 area, the excessive precipitation threat is pronounced whereas large hail and severe wind gusts will likely dominate in the eastern parts of the LVL2 area. It is uncertain whether the clusters / MCSs will continue through the night hours or tend to decay in the evening hours.
...SE Germany, Czech and Slovak Rep., Austria, N Italy, W Romania and Balkans...
The region which surrounds the LVL2 will also get favorable conditions for multicellular storms which may produce large hail and severe wind gusts. Due to less LL moisture advection, the chance for excessive precipitation in that region is lower than in the LVL2 area.
...N Maghreb States...
Some hundred J/kg MLCAPE are forecast over NE Morocco / NW Algeria and the SW Mediterranean in a strongly sheared environment with 15 - 25 m/s of 0-6 km bulk shear. Although strong capping is predicted by the models, a few isolated storms may develop and supportive shear / SRH allow the development of multicells and a few supercells which will pose a threat of marginally severe hail and isolated severe wind gusts. This risk is covered with a LVL1.
