Storm Forecast
Valid: Tue 23 Jun 2009 06:00 to Wed 24 Jun 2009 06:00 UTC
Issued: Tue 23 Jun 2009 06:40
Forecaster: VAN DER VELDE
A level 1 was issued for S Poland, E Czech, Slovakia, N Hungary and NE Austria mainly for excessive precipitation and large hail.
A level 1 was issued for the S Italy region mainly for tornadoes (spouts).
SYNOPSIS
Around a large upper low over southeastern Europe, warm unstable air is advected westward into central Europe. Rather strong pressure gradients are present on the northern flank of the system, with moisture lifting over the Tatra range.
Around the south of the upper low, a shortwave trough affects southern Italy.
DISCUSSION
...S Poland, E Czech, Slovakia, N Hungary and NE Austria...
GFS predicts a stationary convergence zone from S Germany - NE Austria - Slovakia/Hungary, while low level winds continuously transport moisture into the region. MLCAPE can reach over 1000 J/kg flowing SSW-wards along the warm front into a broad occluded Czecho-Slovak region. Westward storm motion will be mostly parallel to the convergence and orographic features (Tatra) which will likely function as trigger. Combined with effective precipitable water of around 30 kg/mē, weak upper level SR-flow, and instability staying around for a large part of the forecast period, it is likely that excessive precipitation will occur and cause problems.
The region also gets more than 10 m/s low-level shear, and moderate (200 mē/sē) SREH and some DLS (10-15 m/s), which will be beneficial for development of intense clustered storms and MCSs in the sunny region which then move westward. Isolated large hail is possible, but a tornado is not ruled out in western parts of the level 1 area where shear is best.
...S Italy region...
Near the southern edge of this region, deep layer shear and forcing are strong, while the rest of the area, close to the core of the upper low, has conditions of superadiabatic low level lapse rates, enhanced 0-3 km CAPE, and slow storm motion: stereotypical conditions for waterspouts (perhaps an isolated landspout).
...Eastern Europe...
Isolated large hail can occur over Ukraine and Belarus, the pattern of instability and forcing is rather complex, but there appears a band of enhanced SREH in the NE Ukraine, SE Belarus region.
