Storm Forecast
Valid: Sat 19 Jun 2010 06:00 to Sun 20 Jun 2010 06:00 UTC
Issued: Sat 19 Jun 2010 04:40
Forecaster: VAN DER VELDE
Levels 1 and 2 were issued for the Balkan primarily for large hail and secondarily for severe convective wind gusts.
A level 1 was issued for W Belarus, Lithuania, W Ukraine mainly for isolated excessive convective rainfall.
SYNOPSIS
A large scale upper low centered over southern Scandinavia covers a large part of Europe. Slight low sea level pressure is found over Scandinavia with an extra center developing south of the Alps. Cool air is transported southward over western Europe in a steady flow between this low and the Atlantic blocking high pressure area. During the afternoon the cold front lies over southern France, Alps, Hungary, eastern Poland and the Baltic states. The most unstable air is present over the western Balkan with MLCAPE over 1000 J/kg. This area also happens to be in moderate deep-layer shear.
DISCUSSION
...western Balkan...
Very weakly capped CAPE is present, as signalled in GFS by small LFC-LCL differences and a deep layer of parcels with CAPE and absent CIN. LCL heights are predicted by GFS at 600-1200 m. While deep-layer shear is not strong, 10-15 m/s 0-6 km, mid-layer shear vectors (1-4 km) are quite enhanced and perpendicular to the NW-SE orientation of low level convergence features, and 0-3 km SREH values reach 100-200 mē/sē, highest along the line N Greece - W Bulgaria - SW Romania, indicating a turning hodograph with potential for strong or rotating updrafts with an elevated chance of widespread large hail. Also isolated severe gusts are possible given the relatively fast calculated storm motion vectors and moderate delta-theta-e values (16K). The 0-1 km shear maximum (10 m/s) over SW Romania could further favor bow echoes in multicell clusters.This clustering is quite likely.
...W Belarus, Lithuania, W Ukraine...
A chance of isolated excessive convective precipitation exists because a plume of CAPE is collocated with its storm-triggering convergence line, with storm motion and shear vectors being along the line. This could lead to prolonged training of cells or anvil precipitation in certain areas with large rain sums as result.
..S Scandinavia...
Under the upper low, weak wind profiles, low-level instability and slow storm motion could enhance chances for spouts.
...Tunisia...
Elevated instability and deep convergence and lifting from shortwave troughs could produce convection embedded in a fast flow (if it survives 30 m/s DLS) with a main threat of creating a dust storm.
