Storm Forecast
Valid: Fri 09 Oct 2009 06:00 to Sat 10 Oct 2009 06:00 UTC
Issued: Fri 09 Oct 2009 06:53
Forecaster: VAN DER VELDE
A level 1 was issued for Corsica, N Italy and Slovenia mainly for excessive rainfall, hail, and waterspouts.
A level 1 was issued for W Russia, N Belarus mainly for the chance of a tornado.
SYNOPSIS
High pressure is present over Iberian Peninsula and another area over S Scandinavia and north-central Europe. In between, an elongated trough with slightly unstable conditions over France, and a more active shortwave trough moving in on northern Italy. An active depression also enters Russia from the Baltic states and Belarus.
DISCUSSION
...Corsica, N Italy and Slovenia...
As the mid level shortwave trough moves into an airmass containing 1-3 MJ/mē ICAPE and >1000 J/kg MLCAPE, storm activity will likely surge across the Ligurian Sea area, and also along the south side of the Alps and Slovenia. While low level winds do not advect lots of moisture, stagnating flow and very moist/saturated profiles are likely to produce local flash flooding from slowly moving, persistent multicellular storms present in the area. Deep layer shear around 15 m/s could bring along some updraft rotation and with the larger cells large hail is possible. A few waterspouts are likely to occur given strong 0-3 km CAPE values and not too strong flow, although near-surface lapse rates are not predicted to be superadiabatic.
The moderate shear conditions for the Balearic islands also may give rise to rotating updrafts in storms, and large hail.
...W Russia, N Belarus area...
A vigorous low with a bubble of unstable air near the core brings along strong low level shear (12-15 m/s in GFS) and tremendous deep layer shear (40-50 m/s!) caused by a jet streak. The instability occurs just to the north of this. This highly dynamic setup might lead to one or more tornadic low-topped supercells.
