Storm Forecast
Valid: Sun 28 Oct 2012 06:00 to Mon 29 Oct 2012 06:00 UTC
Issued: Sun 28 Oct 2012 05:23
Forecaster: VAN DER VELDE
A level 1 was issued for southern Italy and southern Balkan for large hail, severe wind gusts, isolated excessive precipitation, and tornado chance.
A level 1 was issued for the area east of Tunesia mainly for large hail.
A level 1 was issued for the Mediterranean region around Corsica, as well as the NW Adriatic coast region mainly for tornadoes.
SYNOPSIS
An intense Genua low has installed itself. Strong pressure gradients create very windy conditions over a large area, with local orographic wind maxima. Very steep lapse rates and buoyancy predicted near the core of the low around Corsica could combine with vorticity and produce waterspouts by vorticity spin-up mechanisms. With slighter CAPE but more helicity (300 mē/sē), the occlusion over NE Italy might also have some tornadic potential.
The cold front drags mainly over the southern Balkan with persistent storms around Albania with chances of excessive precipitation. Low-level wind shear is larger than 10 m/s in a vast area, enhancing tornado chances, while mesocyclones can easily be supported by long clockwise turning hodographs predicted by GFS. Fast storm motion can easily produce severe gusts, particularly when helped by downdraft buoyancy, which is largest near the CAPE maximum west of Greece.
The limiting factor, however, are indications of capping as seen in the model LFC-LCL difference. These are near zero in the Adriatic, but higher to the south. The airmass is also not overly moist, less than yesterday, which limits precipitation threats. LCL height for example is in the 1000-1500m range. Further east across the Balkan CAPE is shown by models. Again this seems capped for boundary-layer based parcels, and most likely is just elevated, which means that it hardly can profit from the high shear environment there.
The southern Mediterranean east of Tunesia can see a couple of storms or perhaps a linear system along the cold front. GFS produces very high SREH values there which support supercells, but the maximum threat region may well lie beyond the map.
