Am Donnerstag steht am Nachmittag und Abend eine "High shear - low cape" Gewitterlage an, die aufgrund der Dynamik Potenzial für Sturmböen/schwere Sturmböen und Tornados bietet.
Alles anzeigenSpätestens mit Kaltfrontpassage und vor allem postfrontal nehmen sie aber Schauerform an und mit Advektion zunehmend höhenkalter Luftmassen (im Trogbereich -26°C in 500 hPa bei etwa +2°C in 850 hPa) steigt dann auch die Wahrscheinlichkeit für einzelne Gewitter an.
ICON-D2 simuliert bis etwa 200 J/kg ML-Cape vor allem in den mittleren Landesteilen und aufgrund des scharfen Bodentroges steht neben markanter hochreichender Scherung (20 bis 30 m/s in 0 bis 6 km Höhe) auch einiges an bodennaher (Richtungs-)scherung zur Verfügung (um 15, teilweise bis 20 m/s in den unteren 1 bis 2 km).
Dadurch kann im Vorfeld eventueller Schauer- und Gewitterstaffeln einiges an sturmrelativer Helizität zur Verfügung stehen (lokal bis 400 m²/s², dazu teils recht scharf gekurvte Hodografen in den Prognosetemps), so dass durchaus auch rotierende Aufwinde möglich sind.
Entsprechend können neben schweren Sturmböen im Rahmen eventueller kleinräumiger
Bow-Echos auch kurzlebige Tornados nicht ausgeschlossen werden.
Diese Darstellung heißt „Hodograph” und zeigt den Windscherungsvektor über alle Höhen. Die Krümmung im untersten Kilometer (rot) weist auf mögliches Superzellenpotential (Gewitter mit rotierendem Aufwind) hin. Dieses ist morgen erhöht. /V
Alles anzeigenStorm Forecast
Valid: Thu 04 Apr 2024 06:00 to Fri 05 Apr 2024 06:00 UTC
Issued: Wed 03 Apr 2024 22:05
Forecaster: PUCIK/KUZMENKO
A level 2 was issued across E Belgium, Luxembourg and central Germany mainly for tornadoes, severe wind gusts and to the lesser degree for large hail.
A level 1 was issued in a belt from France to Czechia mainly for tornadoes, severe wind gusts and to the lesser degree for marginally large hail.
DISCUSSION
... France to Czechia ...
A fast-moving, low-amplitude short-wave trough will move across the area, propelled by a 50+ m/s jet at 300 hPa. Combined forcing of the trough and an exit region of the jet will yield a large stratiform rain shield. The rain shield will be followed by scattered convection developing within a plume of steeper mid-tropospheric lapse rates, resulting in several hundred J/kg of MLCAPE.
As mentioned in the extended outlook, strong deep-layer shear (> 20 m/s in the 0-3 and 0-6 km layer) will allow for well-organised storms, including supercells and bow-echoes. A favorable kinematic environment will exist for tornadoes with 0-1 km bulk shear between 10 and 15 m/s and 0-500 m SRH locally exceeding 150 m2/s2. Such an environment will be present across a large area. Besides tornadoes, severe wind gusts will also likely occur, especially within the linear segments of upscale growing storms. The intensity of wind gusts will be limited to some degree by a rather modest flow around 1 km. Marginally large hail may occur with supercells.
The convective mode will likely determine the dominant severe weather hazard. All high-resolution models simulate (widely) scattered isolated (super)cells. Only two models simulated an upscale growth into squall lines or bow echoes. Such development is possible either over southern Germany/southwestern Czechia tied to the main rain shield and the strongest forcing. Another eventuality is later on over central-east Germany, which can be boosted by cell interaction.
Compared to the extended outlook, the Lvl 1 area has been expanded to the southwest and the east. A lvl 2 has been introduced to highlight the corridor with the highest expected coverage of severe weather. This corridor was drawn using high-resolution models and their ensembles and the fields such as simulated reflectivity and low-level vorticity.