Storm Forecast
Valid: Tue 24 Mar 2009 06:00 to Wed 25 Mar 2009 06:00 UTC
Issued: Tue 24 Mar 2009 06:53
Forecaster: VAN DER VELDE
SYNOPSIS
A cold front and a sharp upper trough proceed into the Italy/Adriatic area. In the lee of the Alps surface low pressure intensifies. Marginal instability is present but also strong lifting and shear conditions. Within the cold maritime air mass showers can develop with a chance of isolated thunder, which appears most likely near mountains and where shortwave troughs provide forcing, which is reflected in the thunder areas.
DISCUSSION
...Italy, Adriatic countries...
0-6 km shear is elevated to more than 30 m/s due to the jet stream and backed 10m winds. SREH is predicted between 200-400 mē/sē and 0-1 km shear patterns vary but can reach 15 m/s locally. These conditions combined with some instability and strong lift can yield linear thunderstorms with an occasional brief mesocyclone, which are capable of marginally large hail, strong to severe gusts or a tornado... the latter is not unthinkable for the east side of the Adriatic where SREH is largest (600 mē/sē Croatia 18Z) during the evening and night, near the passing occlusion point/low pressure center. Low LCLs are in support.
...Morocco, SW Iberian Peninsula...
On the east flank of a retrograde low, in a warm sector, deep layer shear is around 20 m/s and enhanced SREH, and rather explosive looking developments in satellite indicate a potential for potent multicell (and perhaps supercell) storms with large hail as main threat, in the afternoon most likely over Morocco and more south/eastward than this morning. Over sea instability appears elevated. DCAPE and boundary-relative shear as well as fast MCS propagation suggest there is some chance of severe gusts.
