Storm Forecast
Valid: Mon 24 May 2010 06:00 to Tue 25 May 2010 06:00 UTC
Issued: Sun 23 May 2010 22:58
Forecaster: GROENEMEIJER

A level 2 was issued for eastern parts of Germany, northern Czech Republic, SW Poland mainly for severe wind gusts.

A level 1 was issued surrounding the level 2 area for parts of Germany, the Czech Republic, Slovakia, weastern and southern Poland, and northern parts of Austria and Hungary, mainly for severe wind gusts.

SYNOPSIS

On the wouthwestern flank of a large cyclone over Scandinavia, a mid- and upper-level jet moves from the North Sea into central parts of Europe where it induces frontogenesis. Cyclogenesis is expected over southern Sweden.

DISCUSSION

Level 1 and 2 areas...

At the beginning of the period, partly convective rainfall is expected across northern Germany. Ahead of the cloudiness, plenty of sunshine is expected. Temperatures rising to around 20 C in combination with 13-16 C dew points and cooling mid-levels should render the atmosphere quite unstable with CAPE values around 1000 J/kg. Convective activity within and ahead of the frontal clouds will increase early in the afternoon across Germany. With 15-20 m/s 0-3 km shear, well-organized storms are expected. The mode of organiozation will likely be linear.

As winds at 700 hPa are expected to exceed 25 m/s, severe winds gusts are probable, and most so in the region that sees best overlap of instability, shear and forcing: the level 2 area. Although helicity is rather low, it is rare for such a large overlap of low-level shear and instability in the presence of storms to go by without a single tornado. Thus, one or two tornadoes could certainly occur. Hail threat should be rather limited, but a couple of marginally severe hail events (2-3 cm) could occur, most likely in combination with relatively isolated cells during the afternoon and early evening.

After sunset, the instability is expected to diminish gradually. However, continuing forcing will probably sustain a linear convective system moving eastward across southern Poland that could continue to produce a few isolated severe gusts.