Storm Forecast
Valid: Sat 14 Apr 2012 06:00 to Sun 15 Apr 2012 06:00 UTC
Issued: Sat 14 Apr 2012 07:00
Forecaster: VAN DER VELDE

A level 2 was issued for western Turkey mainly for severe convective wind gusts, tornadoes and large hail.
A level 1 was issued for the eastern and to a lesser extent the southern Balkan mainly for a chance of tornadoes and strong/severe convective wind gusts.
A level 1 was issued for southern Spain mainly for large hail.

SYNOPSIS

A very broad low pressure system and upper trough are in place over Europe. It can be divided into several smaller low pressure systems: one over Scandinavia, one over the Iberian Peninsula and southern Mediterranean, and a large one over Italy and Balkan. Cold air flows southward over western half of Europe, while warm air advects northward on the east side of the low into the Balkan and Turkey. Dynamically, the Iberian/Balearic/Algerian system and the eastern Balkan/Turkey cold front have very well defined high potential vorticity intrusions causing strong upward motion and focus for organized convective development. Over a large area, 250-800 J/kg, locally perhaps 1000 J/kg MLCAPE should be available.

DISCUSSION

...southeastern Europe...

A level 1 marks the zone on the warm side of the cold front where low-level winds blow from southerly directions, sometimes southeast, overlaid by a southwesterly jet which crosses the cold front. This setup creates favorable wind profiles with mostly speed increase and some veering with altitude, good for 25-35 m/s 0-6 km bulk shear vector magnitude, 200 m2/s2 0-3 km storm-relative helicity (SREH) and in the lowest kilometer, due to strong winds and friction, 12-15 m/s shear vectors. The cold front likely triggers a linear convective system for which wind gusts of 25 m/s or more are the primary threat, but embedded or preceding isolated supercells can produce locally tornadoes and large hail. Note that models indicate even higher SREH values to the east over Turkey, but no instability seems to be present there. The level 2 area sees the most optimal timing with regard to heating and mesoscale lifting is maximized to the south as the PV/dynamic tropopause maps show a negative tilting of the trough over time over Turkey.

...southern Spain...

Slight CAPE is collocated with decreasing but still 15-20 m/s 0-6 km shear ahead of a potential vorticity lobe sinking into the region towards Algeria. Together with the low freezing level it is likely that some storm updrafts could organize, perhaps develop rotation and drop 2-3 cm large hail.