Storm Forecast
Valid: Fri 24 Jul 2009 06:00 to Sat 25 Jul 2009 06:00 UTC
Issued: Thu 23 Jul 2009 18:41
Forecaster: TUSCHY
A level 1 was issued for N-Italy and W-Switzerland mainly for large hail and severe wind gusts.
A level 1 was issued for Belarus, Lithuania, Latvia and Estonia mainly for large hail and severe wind gusts.
SYNOPSIS
A broad upper trough shifts eastwards and affects central Europe during the forecast. Very hot and stable conditions persist over the Mediterranean with warm and unstable conditions over eastern Europe in the WAA regime.
DISCUSSION
... N-Italy, Slovenia ...
A trough passes by north of the Alps and the attendant forcing affects the area during the forecast period. At the same time, a cold front is gradually shifting southwards. Up to 1000 J/kg MLCAPE along the S-Alps are a reasonable scenario with 35m/s DLS, so multicells and supercells are possible with a large to very large hail and severe wind gust threat, the latter one enhanced by roughly 20m/s 0-3km shear. Models still disagree in the final coverage and we stay with a level 1 for now. An update may become necessary tomorrow.
... Switzerland ...
Latest GFS run came in a bit more optimistic with moisture recovery and low-end instability release. Shear at all levels is even stronger than to the east, so even non thundery showers could produce wind gusts, approaching the severe criterion. We went with a level 1 for now but this area needs some monitoring, too.
... UK, Ireland, parts of France, Belgium, the Netherlands, Luxembourg, parts of Germany, Denmark, S-Norway and Sweden and NW-Poland ...
Cold mid-levels atop of seasonable surface moisture creates a broad area with daytime driven thunderstorms. Shear increases to the south but overall, DLS of 10-15 m/s will be strong enough for a few multicells with an isolated large hail risk. LCL is low with some LL CAPE release but overall risk of cold air funnels/tornadoes seems to be too slim for a level 1. However a level1 may be anticipated where strongest instability finally evolves (isolated large hail risk with low WBZ).
... Belarus, Latvia, Lithuania and Estonia...
A cold front continues to move northeastwards during the day with strong shear and up to 1000 J/kg MLCAPE in place. Severe wind gusts, large hail and an isolated tornado are the main hazard.
Further to the southeast, shear decreases with increasing instability build-up, so a large hail risk continues with multicells. The activity decreases during the night hours.
