... Austria, extreme E Germany, the Czech Republic, parts of Slovakia and Poland ...
A leisurely eastward moving cold front serves as focus for scattered to widespread convective initiation (CI). Differences in the eastward progression are still present in model fields, but prefrontal air mass qualitiy is more or less the same: good BL moisture beneath marginal mid-level lapse rates result in mainly 500 J/kg MLCAPE north/northeast of the Alps with higher values over Austria and Poland ( where locally better BL moisture exists). Regarding the wind field, a 15-20 m/s 500 hPa jet streak moves from E-Germany into NW Poland, where DLS therefore acquires values supportive for a few better organized multicells. Weaker shear (below 15 m/s 0-6 km shear) is forecast towards Austria and SE Poland, but better CAPE may offset weaker shear.
Main uncertainty will be the placement and strength of a convective cluster over SE Germany/N-Austria and the Czech Republic, ongoing from the overnight hours. Southbound moving outflow boundary may seriously impact the forecast over NE/E-Austria, as cold front (modulated by that outflow) may be displaced already further to the south than models currently forecast.
Otherwise, with no real mid-level disturbance forecast (despite weak signals in PVU fields), ongoing diffluent streamline pattern and weak to zero CIN along/ahead of the cold front, early and scattered to widespread CI is expected. During the early (more discrete) stage, a few large hail and strong wind gust events are possible. However, rapid clustering is expected with a trend more to a heavy rainfall risk. A heavy rain level 1 situation is expected with slow moving storms over E/NE Austria, the Czech Republic, W-Slovakia and SW Poland and the hail and heavy rain risk further to the N/NE.
We excluded SE-Germany, N-Austria and SW-Czech Republic from the level 1 due to the aforementioned uncertainties. If no overnight cluster occurs those areas may see a transient level 1 risk (however no update will be issued for that). The lightning areas remain more aggressive to include the worst-case scenario (no overnight cluster).
Österreich befindet sich in einer südwestlichen Höhenströmung mit dieser sehr feuchtlabile Warmluft herangeführt wird. Eingelagert in der Südwestströmung liegt eine Luftmassengrenze über dem Alpenraum, wo sich ausgehend dieser Grenze bis zum frühen Nachmittag erneut eine Feuchtekonvergenz formieren wird, diese in weiterer Folge nach Südosten voranschreitet & einige teils heftige Gewitter mit sich bringt. Nach Abzug der Konvergenz lässt die Unwettergefahr rasch nach, wobei einzelne Gewitter auch bis in die Nacht hinein fast überall möglich sind.
& vergessts Estofex heute wieder mal Leute
Mit besten & lieben Grüßen Obmann Hans-Jürgen Pross
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