Storm Forecast
Valid: Wed 04 Mar 2009 06:00 to Thu 05 Mar 2009 06:00 UTC
Issued: Tue 03 Mar 2009 21:23
Forecaster: GROENEMEIJER

SYNOPSIS

Wednesday at 0600 UTC... a longwave trough is located over western Europe. A sharp embedded shortqave trough stretches from the western Mediterranean across NW Algeria into eastern Morocco. As a strong 80-90 m/s north-northwesterly jet across the eastern North Atlantic propagates southward, the longwave deepens and the embedded shortwave moves east-northeastward as a rather intense feature with a strong 40-50 m/s mid-level-jet ahead of it until 00-03 UTC. At the same time cyclogenesis occurs over the Tyrrhenean Sea.

DISCUSSION

Sicily, south Italy, parts of the Balkan west coast...

The 12 UTC GFS as well as a majority of the WRF runs available, simulate significant amounts of convective precipitation to occur along a cold front passing Sicily and southern Italy in the 18-00 UTC time frame. About 300 m2/s2 of storm-relative helicity is also predicted ahead of the front, so that rotating updraughts are possible. Considering low-level wind shear will be well in excess of 10 m/s, some threat of tornadoes will be present. A few marginal large hail events appear possible as well. Limiting factor will be the overall instability which will probably not exceed a few 100s of J/kg, and the likelihood of linear convection. These keep me from upgrading to level 2 for Sicily and extreme south Italy at the moment in a situation that appears to have good forcing and wind shear. The Balkan coast will probably not be affected by storms until after 0000 UTC.