A Severe Threat 1 has been issued for SE France, N Italy, parts of Switzerland and Austria and for SE Germany, mainly for large hail, excessive precipitation and severe wind gusts

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Model consistency, additional remarks

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A Severe Threat 2 has been issued for parts of Benelux and northwestern Germany mainly for severe to locally significant severe wind gusts, severe convective precipitation, tornadoes and to a lesser degree for large hail

A Severe Threat 2 has been issued for eastern France mainly for severe wind gusts, excessive convective precipitation and large hail

A Severe Threat 1 surrounds the both severe Threat 2 mainly for severe wind gusts, large hail and excessive convective precipitation

The upper pattern across Europe is influenced by a deep ridge aligned from the Mediterranean to Scandinavia which is flanked by two troughs over Russia and the northern Atlantic, respectively.
Enhanced southwesterly flow aloft on the eastern periphery of the latter trough forms the basis for severe thunderstorm activity across central Europe on Thursday.
As a small secondary trough passes northern Spain a baroclinic development is triggered in the lee of the Pyrenees. The arising Saphiro-Keyser-like surface low advances northeastwards with the southwesterly background flow.

…Central Europe…

North to the aforementioned low, strong warm air- and moisture advection favour a north- and northwestward return of an potentially unstable subtropical airmass (which was displaced eastward by a cold front on Wednesday). ML CAPE from 1000-1500 J/kg is forecast to cover most parts of Germany as well as over eastern France with the highest values to the East.

The uncertainties of the overall set-up concern the track of the low as well as the spatio-temporal distribution of the cloud- and precipitation fields. As usual, the latter will have a great impact on the exact amount of CAPE which will be available in the warm section. Especially the cloud coverage along the warm front is simulated quite differently by the models at this time. As a model mean, the low’s core can be anticipated somewhere between Be-Ne-Lux and NW Germany around 15 UTC.

Apart from instability, confidence is high that rather elongated and well curved shear vectors will be found in the vicinity of the surfaces low trace from central and eastern France to the northwestern half of Germany. 0-6 km bulk shear reaches 18-25 m/s in this region but most horizontal vorticity will be confined to the lowest 3 km of the atmosphere.
In general, latest model consensus suggests that instability and shear are best superimposed in a corridor from eastern France diagonal across north-central Germany.
Here most hi-res and convection permitting models predict a well defined convective line with bowing segments, as the low’s cold front rapidly pushes northeast during the afternoon/evening. Such a scenario seems quite plausible as a consequence of the strong 0-3 km shear.
With the linear segments, severe straight line winds caused by convective vertical mixing are likely – even some isolated significant severe events are possible (> 30 m/s).

In case of more discrete updrafts, which are possible at the warm front (NW Germany) or generally in the Severe Threat in western France, there is a chance for the development of supercells capable of producing large hail, severe wind gusts and tornadoes.

Northwest and southeast of the corridor, the probability for a distinct overlap is reduced either due to lower shear (southeast) or a smaller amount of CAPE (northwest). Nevertheless, severe potential is also augmented in these regions. In extreme NW Germany/Netherlands, strong low level shear along with remarkable curved hodographs leads to an enhanced tornado threat, particularly if more discrete cells manage to develop. Contrary, across southern Germany where storm mode is forecast to be less linear, some large hail events are possible with the highest CAPE values. In addition a 10% wind line has also been introduced to account for dry downbursts favoured by the high and well mixed boundary layer, as well es those model solutions that show a more southern track of the convective line.

Besides the cold front convection, some cells may also initiate over eastern Germany. Here, the severe potential is somewhat lower, but Large hail and excessive precipitation are possible as well.

Model consistency, additional remarks

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A Severe Threat 1 has been issued for parts of Be-Ne-Lux and northwestern Germany mainly for severe wind gusts, excessive convective precipitation and to a lesser degree for large hail

A Severe Threat 1 has been issued for most parts of Germany, parts of the Czech Republic, extreme western Poland and parts of Austria and Switzerland for large hail (especially across south eastern Germany), excessive convective precipitation and to a lesser degree for severe wind gusts

A Severe Threat 1 has been issued for parts of France mainly for excessive convective precipitation, large hail and to a lesser degree for severe wind gusts

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Model consistency, additional remarks

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A Severe Threat 2 has been issued for northern France, parts of Be-Ne-Lux and extreme western Germany mainly for severe wind gusts (a few of them could be significant severe), large hail and excessive convective precipitation

A Severe Threat 1 surrounds the Severe Threat 2 mainly for severe wind gusts, excessive convective precipitation and to a lesser degree for large hail

A Severe Threat 1 has been issued for parts of Austria mainly for excessive convective precipitation

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Model consistency, additional remarks

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A Severe Threat 2 has been issued for southwestern Germany and northern Switzerland mainly for (extremely) excessive convective precipitation, large hail and to a lesser degree for severe wind gusts

A Severe Threat 1 surrounds the Severe Threat 1 for the same hazards, but with less probability/severeness

A Severe Threat 1 has been issued for southern Sweden mainly for excessive precipitation, and to a lesser degree for medium size to large hail and severe wind gusts

A Severe Threat 1 has been issued for south-eastern Poland, northern Slovakia, extreme western Ukraine and parts of western Belarus mainly for excessive precipitation, large hail and to a lesser degree for severe wind gusts

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Model consistency, additional remarks

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