Storm Forecast
Valid: Tue 16 Jun 2009 06:00 to Wed 17 Jun 2009 06:00 UTC
Issued: Tue 16 Jun 2009 05:55
Forecaster: VAN DER VELDE
A level 1 was issued for N Italy, Slovenia, S Hungary, NW Balkan mainly for large hail and severe wind gusts.
A level 1 was issued for Spain mainly for large hail.
A level 1 was issued for N Romania, SW Ukraine, N Moldova mainly for large hail.
A level 1 was issued for W Russia mainly for tornado and gust threat.
SYNOPSIS
A cold front moves farther into Europe with a prefrontal band of slightly unstable airmass from N Italy into Romania, northward to W Russia. A low pressure area and active occlusion is forecast to track over Belarus north along the frontal zone. On the cool side of the front over Germany, instability and convective cloud depth are predicted to be sufficient for some thunder, and an isolated funnel or landspout is possible.
More serious convective weather should occur mainly over Italy and NW Balkan, where strong deep layer shear is caused by the presence of the jetstream.
DISCUSSION
...W Russia...
The 400 mē/sē 0-3 km SREH combined with some signs of instability along the occlusion, low LCL and strong LLS can be sufficient for a tornado threat, if instability indeed realizes. The low is vigorous, with a strong PV band into its rear. The level 1 corresponds with the area where GFS 18Z places marginal but uncapped instability.
...N Romania, SW Ukraine...
A marginal level 1, given rather low instability, but decent DLS of 15 m/s, LLS greater than 8 m/s over a large area, which could support large hail from a possible supercell. SREH is highest in the early afternoon with values of 100-250 mē/sē.
...N Italy, NW Balkan...
Under DLS conditions of 20-25 m/s, CAPE possibly reaching 1000 J/kg (usually GFS underestimates this in the lee of the Alps) supercells should be possible, in particular near southern Hungary where the SREH is predicted to be over 200 mē/sē. Large hail is then a logical result, while also severe gusts are likely with DCAPE and delta-theta-e being elevated. An MCS may grow out of initial storms. However, the airmass south of the frontal zone appears rather capped from the surface. The storms in the level 1 will likely move along the front in support of isolated local flash flooding, but LCL heights and effective PW are not very favourable.
...Spain...
At least 10-20 m/s of DLS is forecast for the NE half of Spain, with a SREH maximum in the center of more than 300 mē/sē in several GFS runs. The shear is at least sufficient for multicell clusters, and may include supercells where SREH is encountered. Large hail is the primary threat. Bunkers storm motion results in small speed of supercells, which may then cause local flash flooding.
