Storm Forecast
Valid: Wed 17 Jun 2009 06:00 to Thu 18 Jun 2009 06:00 UTC
Issued: Tue 16 Jun 2009 16:47
Forecaster: TUSCHY

A level 1 was issued for Albania, Macedonia and SW-Bulgaria mainly for large hail.

SYNOPSIS

Hot/stable conditions sprawl over the Mediterranean with strong WAA still present over far E-Europe ahead of the persistent NE-Europe trough. A cold front crosses UK/Scotland and Ireland from the west heralding cool/wet atmospheric conditions.

DISCUSSION

... Albania, Macedonia, SW/W-Bulgaria and the E-Adriatic coast...

A southward oozing boundary provokes scattered thunderstorms. The environment is characterized by a moist, prefrontal boundary layer beneath steep lapse rates and therefore abundant MLCAPE release. 15-20m/s DLS and enhanced directional shear next to the front itself cause hail to be the main hazard and even very large hail is possible, mainly over Albania, Macedonia and W-Bulgaria. Current thinking is that discrete supercells are possible, as prefrontal airmass is well capped and frontal forcing remains on the weaker side, but higher thunderstorm coverage is questionable, so a level-2 is not yet anticipated.

The same for parts of Italy although overall lift/forcing will be weaker. Isolated storms are forecast with marginal hail/strong wind gust the main risk.

...The Pyrenees ...

Geopotential heights increase with warm atmosphere/weak lapse rates present, so any convective activity will be bound to the orography or maximized surface moisture advection over extreme SW-France. We're still sceptical about the coverage of storms, but latest surface dewpoint analysis already had readings in the mid tens with 12Z soundings showing a passable depth of that moist layer. We stick with WRF for now, which breaks out convection along the orography and S-France. Slow storm motion could cause extensive rain amounts next to isolated large hail and strong wind gusts.

Thunderstorms over NE Poland, Lithuania, Belarus and W-Ukraine will be mainly marginal hail producers, as WBZ stays low, but no severe risk is expected.