Storm Forecast
Valid: Sun 10 Mar 2013 06:00 to Mon 11 Mar 2013 06:00 UTC
Issued: Sun 10 Mar 2013 10:36
Forecaster: VAN DER VELDE
A level 1 was issued for southern Spain mainly for large hail and tornado chance.
A level 1 was issued for NE Algeria/NW Tunesia mainly for large hail.
A level 1 was issued for parts of Sardinia, Corsica and W Italy mainly for large hail..
SYNOPSIS
A sharp division between cold weather in northern Europe and warm, slightly unstable weather in southern Europe today. Temperatures are decreasing on the cold side of the front in the southern UK, Netherlands, Belgium, northern France and northern Germany, while one of the first springtime continental thundery days of the year unfolds over France and Iberian Peninsula (mainly). The Celtic Sea low has an extension toward central Europe, and isolated thunderstorms in a weakly sheared environment may occur across a large region, mainly triggered by higher terrain. Stronger flow and shear occurs from southern Spain to Sardinia, central Italy and the Balkan in combination with some CAPE. A shortwave passes from western Mediterranean into Italy, and another from Atlantic/Portugal to southern Spain onwards into the western Mediterranean, where CAPE develops in the late hours (00-06Z) which may be capped intially.
DISCUSSION
...southern Spain...
More humid unstable air arrives from the Atlantic. A shortwave trough marked sharply by a PV intrusion in GFS is arriving during the afternoon. Some 20 m/s 0-6 km shear or more is predicted to be in place, mostly in straight hodographs, and can favor supercells, while low level shear can reach 7-10 m/s. The LCLs are quite low which enhances chance of tornadoes a bit.
...Sardinia-Italy area...
This area is under 20-30 m/s 0-6 km shear with straight hodographs. The result may be a supercell or two with a large hail chance. At the west coast of Italy, a tornado cannot be ruled out as low level shear increases to over 15 m/s during the evening.
...Tunesia area...
Hodographs are turning nicely clockwise with height in this region, yielding significant storm-relative helicity (250 mē/sē) which in combination with CAPE (not much, but probabbly sufficient) can produce supercell storms with large hail.
