ESTOFEX Storm Forecast for Tuesday and Wednesday
Valid: Tue 11 Jun 2019 06:00 to Wed 12 Jun 2019 06:00 UTC
Issued: Mon 10 Jun 2019 20:47
A level 2 was issued for parts of Germany, Poland and the Czech Republic for large hail, severe wind gusts, excessive precipitation and tornadoes.
A level 1 surrounds the level-2 area and it was issued for the same countries mainly for large hail and severe wind gusts.
A level 1 was issued for E Denmark and S Sweden for excessive precipitation.
A level 1 was issued for N Italy, S Austria and Slovenia for large hail, severe wind gusts and excessive precipitation.
A level 1 was issued for parts of Latvia and Lithuania, mainly for large hail and severe wind gusts.
A level 1 was issued for W Balkans mainly for large hail.
A level 1 was issued for Turkey for large hail, severe wind gusts and excessive precipitation.
The positively-tilted trough in W Europe and the amplifying ridge in eastern Europe create a very favourable environment for deep moist convection in Central Europe.
The south-southwesterly flow in mid-levels increases the deep layer shear over warm and moist air masses. At the surface, a low-pressure system over Germany creates strong low/mid-level helicity providing rotation to any storm that will form inside the level-2 areas.
Over E Europe several PVA can be found in the latest model outputs, providing lift to unstable air masses in addition to strong diurnal heating.
Even though storm activity is forecast to be widespread, only locally the storms may become severe, due to the absence of strong DLS / CAPE overlap.
Germany, Poland and Czech Republic
A strong convergence zone is forecast in this part of Europe, where all thermodynamic parameters are conducive for the development of severe thunderstorms.
MLCAPE is forecast to exceed locally 2500 J/kg, overlapping with 15-20 m/s DLS and 10-15 m/s 0-3km bulk shear.
The first storms should form just after 12z in Germany and the Czech Republic and they will be able to become quickly supercells, taking advantage of the 200-300 m2/s2 SREH0-3km on the periphery of the low-level cyclone.
Large to very large hail is expected, as well as severe wind gusts, especially near the borders of Germany and Poland given the high delta-theta-e values. In the southern parts of level-2 and level-1 areas, the low-level directional shear and the low LCLs may help some updrafts to develop tornadoes.
E Denmark and S Sweden
The southern flow brings some very unstable air masses over southern Scandinavia, but they will be strongly capped. A short-wave impulse crossing the area in the afternoon does not seem to able to trigger convection.
A level-1 was issued for excessive precipitation events in the early morning and late afternoon/night of Tuesday 11/06 mostly from elevated storms coming from the south.
N Italy, S Austria and Slovenia
Strongly sheared unstable air masses are also found in N Italy and Slovenia, where models show the development of more than 2000 J/kg MLCAPE in the afternoon of Tuesday 11/06.
Strong DLS and 0-3km bulk shear show the potential of supercell formation and the main threat will be large hail and severe convective wind gusts, especially in the Po valley.
Latvia and Lithuania
Another convergence zone is forecast over this area where cold air masses meet the warm and moist plume from C Europe. GFS forecasts more than 2500 J/kg MLCAPE with an overlap of 10-15 m/s of directional DLS.
Storms that will form inside this environment will become severe and they are expected to travel long distances, with some of them becoming supercells. Large hail and severe wind gusts are the main threats.
Turkey and the Balkans
Mostly diurnally driven thunderstorms, under the influence of upper PVA maxima may become locally severe in the afternoon of Tuesday 11/06. DLS will remain below 15 m/s and mostly close to 10 m/s, so storms will mostly be isolated.
The main threat in both Balkans and Turkey is large hail, as high CAPE is concentrated in the mid-levels with dry slots below 5 km AGL indicating also the potential of severe wind gusts at the surface.
These type of events is why I think that for safety it is very important to have a Windy Alert Notification automatically sent whenever a CAP Alert is issued for that location (per my suggestion here: https://community.windy.com/topic/8268/windy-alert-notification-for-cap-alerts-weather-warnings)
Violent and extreme weather events are becoming more common and for the average person, who may not be monitoring the weather closely, these events can arrive suddenly and unexpectedly causing risks to lives and property.