Storm Forecast
Valid: Fri 29 May 2009 06:00 to Sat 30 May 2009 06:00 UTC
Issued: Thu 28 May 2009 15:35
Forecaster: TUSCHY

A level 1 was issued for Sicily, extreme S-Italy and Greece mainly for large hail.


SYNOPSIS

Strong cut-off over east-central Europe remains stationary. Numerous disturbances around its periphery bring unsettled conditions for most parts of central Europe. High pressure dominates the rest of Europe with a low-end shower/thunderstorm risk over parts of Spain and NW-Algeria.

DISCUSSION

... Sicily and Greece ...

A strengthening trough enters the highlighted area from the NW during the morning hours and continues eastwards. Surface dewpoints in the mid tens and a cool mid-troposphere result in modest instability release with roughly 1000 J/kg MLCAPE. 0-6km bulk shear of 10-20m/s is enough for a few organized storms with an isolated large hail and strong wind gust threat. Over Sicily thunderstorms decrease after sunset but they continue to develop over Greece until 06Z.

... Extreme SE-Germany , parts of the Czech Republic and Austria ...

Forecast is not straightforward and still contains some uncertainties. Pretty dry air entered N/NE-Germany yesterday and kept going to the south/southeast. Surface dewpoints were in the lower single digits and there is no doubt that this quite hostile boundary layer environment affects the highlighted area during the forecast. Some recovery is possible during the day due to weak moisture advection from the north and some evapotranspiration and that's already enough for some low-end instability release, given very cold mid-levels. Strong forcing crosses the area from the NE and ought to support isolated to scattered thunderstorms. EL fields show a slight chance for deep convection in 20-25m/s DLS. Given low WBZ, strong shear and steep lapse rates, the main hazard will be hail, probably below severe criterion. Strong wind gusts are possible, too. Thunderstorm chances decrease rapidly during the evening hours, as well mixed boundary layer becomes more stable.

... N-Italy ...

Better moisture along the coastal areas of the NW Adriatic Sea and incoming trough from the north could still spark an isolated thunderstorm mainly over N-central Italy. If storms grow deep into the troposphere they could take profit of 30-40m/s DLS, producing isolate large hail and strong wind gusts, but overall risk and coverage remains too low for a level area.