Storm Forecast
Valid: Sun 06 Jun 2010 08:00 to Mon 07 Jun 2010 06:00 UTC
Issued: Sun 06 Jun 2010 08:48
Forecaster: SCHLENCZEK
A level 2 was issued for Belgium, Luxembourg, NE France and W Germany mainly for widespread severe wind gusts and large hail and to a lesser extent for tornadoes and excessive rainfall.
A level 1 surrounding the level 2 was issued for most parts of W Germany, France, Benelux and NE Spain mainly for large hail and severe wind gusts.
A level 1 was issued for E Lithuania, Latvia and N Belarus mainly for severe wind gusts.
A level 1 was issued for the Bosporus region and W Turkey mainly for excessive rainfall.
SYNOPSIS
Between an upper trough over the British Isles and a ridge over the western Mediterranean, warm and moist air is advected into France and W Germany by a southwesterly upper flow. The cold front which separates the subtropical airmass from marine polar air is initially located along a line from E England via NW France towards extreme W Spain and Gibraltar. Forced by an approaching shortwave trough, the northern part of this front will shift eastward, crossing central and eastern Germany on Monday morning. At the northern tip of the subtropical airmass, cyclogenesis is forecast with a surface low moving towards the W Baltic Sea. The southern part of this front is influenced by another upper shortwave trough which will cross S Iberia on Sunday afternoon.
Another upper low is centered over the Aegean Sea and will move eastward. Ahead of this low and another strong low pressure system over the Barents Sea, a very hot continental airmass is advected from the Arabic Peninsula towards N Russia. Along this cold front which is located east / northeast of our forecast area, severe thunderstorms should be possible.
South of the aforementioned low pressure system, marginal instability should be present over the S Baltics and parts of Belarus in the vicinity of a westerly 30 m/s jet streak at 300 hPa.
DISCUSSION
...Spain...
Moderate instability should be created ahead of the trough in an environment with 10 - 15 m/s deep layer shear. Most storms should be multicells, capable of producing marginally severe hail and severe wind gusts. After sunset, convective activity will rapidly decrease as most CAPE vanishes.
...E-central France, S Benelux, W / SW Germany...
Ahead of an upper shortwave trough, warm and moist air is advected into parts of east-central France, Benelux and W Germany. CAPE is forecast to be in a range of 1000 - 2000 J/kg in an environment with 10 - 15 m/s deep layer shear, locally up to 20 m/s. In the eastern parts of this discussion part, the airmass is capped and convective initiation is expected to occur in the late afternoon. Most storms over eastern France tend to become multicellular and may merge into a linear MCS. The main threat is expected to be large hail and severe wind gusts. Ahead of this system, some isolated storms may become supercellular, posing a threat of large hail and severe wind gusts. A tornado is not ruled out as LCL heights should be in a range of 800 - 1500m AGL and LLS may be locally enhanced. The large hail / tornado threat should diminish in the late evening hours as most CAPE is surface-based.
...Lithuania, Latvia, N Belarus...
A small region of low-end instability is centered under an upper jet streak, leading to 20 - 25 m/s deep layer shear. Some storms that develop in this environment may produce isolated severe wind gusts. Thunderstorm activity should start in the morning hours and will come to an end in the late evening.
...Aegean Sea, W / SW Turkey, Bosporus region...
Some hundred J/kg CAPE are forecast in this region and the position of the upper low will lead to a training effect especially in W Turkey. Numerous multicells will develop and tend to merge into large mesoscale convective systems. The main threat will be excessive rainfall as the region will be crossed by convective cells for a long time and the upper level wind field is quite weak. Locally, some marginally severe hail and an isolated severe wind gust may occur.
