Storm Forecast
Valid: Tue 22 Aug 2006 06:00 to Wed 23 Aug 2006 06:00 UTC
Issued: Tue 22 Aug 2006 09:21
Forecaster: VAN DER VELDE

SYNOPSIS

A longwave upper trough is situated over central Europe, with its center over southern Scandinavia. A cold front at the nose of the upper trough over southern Ukraine with warm, moist airmass ahead of it under the jetstream is generating strong thunderstorms.

DISCUSSION

...southeastern Ukraine...

With moderate instability, and strong shear conditions near the jet (15-20 m/s DLS, 7-12 m/s LLS), the shortwave upper trough digging trhough the area creating strong lift, severe thunderstorms (squall line, supercells) will affect the region with a chance of organized severe gusts (20 m/s winds will be present at 700 hPa), large hail, and possibly also a few tornadoes (LCL heights forecast by GFS <1000m)

...Slovenia area...

Strong deep layer shear (>20 m/s) is present under the jet stream in an area forecast to have marginal instability and some precip signals are present in the GFS model. Isolated storms may develop and become supercells, with a chance of mainly large hail and severe gusts. Low-level shear will likely remain insufficient for tornadogenesis.

...northern Germany, southern Scandinavia, ...

Organized convection in the morning associated with a small trough affects the northwestern Germany area. 00Z soundings show very moist airmass with good low-level buoyancy and weak surface level winds, normally good for waterspouts, and GFS model indicates some enhanced low/deep-level shear over land, keeping tornado chances up. The rest of Scandinavia (and maybe Poland) may see isolated spout activity, mainly with linear convection over the warm Baltic Sea, where steep near-surface virtual temperature lapse rates will be in place in a calm wind environment.