Storm Forecast
Valid: Wed 19 Aug 2009 06:00 to Thu 20 Aug 2009 06:00 UTC
Issued: Wed 19 Aug 2009 01:04
Forecaster: PUCIK

A level 1 was issued for Northern Algeria mainly for large hail and severe wind gusts.

SYNOPSIS

At midlevels, an amplifying ridge will build up from the Central Mediterranean into Scandinavia, bringing stable weather conditions across most of Central Europe. From the west a trough with slow eastward motion will affect the region of Eastern Atlantic and British Isles. A strong, south-southwesterly mid level flow will establish between these two features. At the rear flank of the ridge a plume of High Theta-E airmass will be advected over France and BENELUX, spreading northwards. To the east, an almost stationary trough over Eastern Europe will slowly turn into a cut-off low. At the surface, a large high will have settled over Central Europe by Wednesday morning, without any significant movement during the forecast period. To the east, a surface low will slowly fill while a deep low over Eastern Atlantic with center over Iceland will start influencing the weather conditions over Western and Northwestern Europe.

DISCUSSION

...Northern Algeria...

A belt of strong mid-level flow will be present over the moderately unstable airmass, with MLCAPEs over 1000 J/kg and DLS up to 20 m/s. Slightly veered flow will also lead to enhanced SREH values, especially around the coastal areas, Conditions will be quite favorable for well organised convection, including supercells. Storm coverage is questionable, however, as no obvious synoptic scale forcing should be in place. Current thinking is that isolated storms might form, especially over the mountainous areas. Thanks to the moderate shear and moderate instability being released in the updrafts, a large hail is possible with the stronger storms. Very dry tropospheric profiles are also suggestive of strong cold pools and a downburst can not be ruled out.


....Northern Italy...

Diurnally driven thunderstorms are expected over this region, forming in moderate MLCAPE values, locally over 1000 J/kg. In a weak wind shear regime, they should stay poorly organised, mostly in the form of multicell clusters. Marginally severe hail or wind gusts can not be completely ruled out with the stronger storms, despite the fact that the Level 1 is not warranted at the moment.