Valid: Mon 30 Mar 2015 06:00 to Tue 31 Mar 2015 06:00 UTC
Issued: Mon 30 Mar 2015 03:48
Forecaster: VAN DER VELDE
A level 1 was issued for parts of central Europe mainly for isolated tornadoes, large hail and severe wind gusts.
At 12Z lows are present over the Baltic Sea, Italy, west of Scotland and southeast of Iceland. Cold unstable airmass has invaded northern central Europe behind the cold front of the Baltic low which stretches from the Alps to Ukraine and Lithuania. A northwesterly jet branch blows over Scotland to northern Italy, rounding the unstable airmass. Strong low level flow across central Europe enhances low-level wind shear. The strongest lift should occur over the southern half of the cold front, where CAPE however is smallest. Most CAPE is associated with the trough over northern Germany and Poland.
The Scottish low will affect the British Isles with non-convective 25-30 m/s wind gusts during evening and night.
0-1 km shear of 10 m/s or greater is present over a large area and can help isolated tornadoes to form from the better organized storms. But the deeper shear to increase chances of tornadogenesis further is only present along the fringes of the unstable airmass, across central Germany, Austria, northeastern Italy and along the cold front. Hail is likely and may reach marginal 2 cm in a few locations if the storm profits from shear. Wind gusts are probably not severe in most locations as 1-3 km mean winds stay mostly below 20 m/s. GFS model suggests strong lapse rates and slight CAPE development southeast of the Alps in the warm airmass under incredible shear conditions (60 m/s 0-6 km vector). With moisture barely reaching 6 g/kg it is unlikely that any storms manage to form and stay alive. If so it could produce large hail.
Note the supercell composite parameter signals resulting from strong SREH and minimal CAPE over UK and southern Germany. These can be effectively ignored as they occur under stable mid level lapse rates.