Storm Forecast
Valid: Wed 11 May 2016 06:00 to Thu 12 May 2016 06:00 UTC
Issued: Tue 10 May 2016 22:03
Forecaster: PUCIK

A level 1 was issued for E France mainly for marginally large hail and excessive precipitation.

A level 1 was issued for parts of central Italy and of the Adriatics coastline mainly for marginally large hail.

A level 1 was issued for NE Poland, S Lithuania, W Belarus and W Ukraine mainly for marginally large hail and to the lesser extent for severe wind gusts.

SYNOPSIS

Quite complex situation is observed over Europe which will leave a large portion of the continent with decent chances for at least isolated electrified DMC. The first main feature is a large cyclonic vortex centered currently near western Iberia. Its eastern flank will rapidly amplify eastwards in conjunction with the passage of a sharp short-wave trough ejecting from the base of the vortex in strong southwesterly flow. Large precipitation shield will form in the left exit region of jet-streak near western Alps and on the cool side of the wavy frontal boundary developing over France. Second feature will be a pool of low geopotentials stretching from Scandinavia through Poland, Slovakia and Ukraine towards the Black Sea with separate low centers over Finland / northwestern Russia, eastern Slovakia and the Black Sea.

Thunderstorms will be associated especially with the aforementioned lows at mid to upper troposphere, filled with cool airmass and thus resulting in steeper lapse rates.

DISCUSSION

... E France ...

North of the wavy frontal boundary and a slightly deepening surface low, dewpoints between 12 to 15 deg C are observed currently. Models simulate build up of latent instability with MLCAPE values on the order of hundreds J/kg, perhaps locally close to 1000 J/kg, also depending on the amount of heating during the day. Abundant cloudiness and morning precipitation may become a negative factor in this scenario. Scattered to widespread initiation is expected in uncapped environment, especially along the convergence zone of the wavy boundary. DLS values will be marginal for organised convection, increasing towards south and towards the evening hours. Still, 10 to 15 m/s of DLS may yield a few better organised multicells. These may be capable of marginally large hail and/or excessive precipitation.


... Central Italy to the Adriatics coastline ...

Storm formation in this region will be associated with the passage of a short-wave and the approach of left exit region of the jet-streak. Models do not show significant instability with MLCAPE on the order of hundreds J/kg, likely due to rather cool sea and dewpoints only between 12 - 16 deg C over the region. Still, as jet-streak approaches, an overlap of strong DLS and a the latent instability will exist, with some potential for supercells and subsequently, large hail. Severe wind gusts are not completely ruled out either.

... NE Poland through S Lithuania, W Belarus and W Ukraine ...

Isolated to scattered convection will initiate over the area under the DLS below 10 m/s. Thus, we expect disorganised pulse storms, in the form of single cells or short-lived multicell clusters. Nevertheless, thanks to the cool mid-troposphere, stronger cells may produce marginally large hail. If strong heating creates high T-Td depressions near the surface, local downbursts may occur as well.