Storm Forecast
Valid: Sat 02 Jun 2007 06:00 to Sun 03 Jun 2007 06:00 UTC
Issued: Sat 02 Jun 2007 09:22
Forecaster: VAN DER VELDE

SYNOPSIS

An mid/upper cut-off low dwells slowly southward with its center just west of Italy. The associated surface pressure field weakens during the period. High pressure dominates northern Europe. Between these systems, the flow has generally an eastern and northern component and contains some waves. At 15Z, a mostly stationary satellite mid level low affect southeastern Poland, northern Romania, Slovakia and Hungary, and a a mid level shortwave trough will be situated over western Germany and Benelux and move slowly westward.
Modest instability is forecast to develop diurnally in a large area over Europe as indicated. Deep layer shear around the Italian low is mostly not co-located with instability. In the western Ukraine area there will be moderate deep layer shear in place with stronger instability.

DISCUSSION

...W Ukraine, N Moldova, S Belarus, SE Poland, E Slovakia....

In this area north of the satellite low organized QG lifting should be present, while moderate deep layer shear is indicated, from >10 m/s over 0-6 km in southern Poland, to over 15 m/s in the western Ukraine/Belarus (into Moldova and northern Romania), where 0-3 km SREH is progged to reach values up to 350 m2/s2 at 18Z. Good low-level convergence should be present in this place, and a deep layer of parcels providing MLCAPE of a few hundred J/kg, also indicated by 00Z soundings.
Expect storms to develop rotating updrafts through the level 2 area (i.e. supercells) and organized multicells as the main mode over the level 1 area. Both may produce large hail, chances (and probably size) larger towards the east where most SREH and convergence is situated. Enhanced delta-theta-e and maximum downdraft buoyancy (>15K both) suggest a significant risk of severe gusts. LCL heights are under 1000 m more westward and during early evening also collocated with >10 m/s 0-1 km shear. This suggests an isolated tornado should belong to the possibilities as well especially in northern parts of the level 2 area. An MCS may turn out to be the main mode into the evening and reach into southeastern Poland and yield some severe gusts.

...Italy area...

Have indicated a level 1 for the area where potential is thought to exist most for waterspouts. Fairly weak flow and locally enhanced low-level CAPE and low LFC heights such as the Milano 00Z sounding may spin up spouts especially at wind shift lines. The northern Adriatic looks most favourable but cannot exclude them elsewhere as well. Storms may cluster mostly over northern Italy towards the evening, when the jet somewhat overlaps instability. Large amounts of small to marginally large hail may fall locally.