06-09-2018 04:43 | Estofex | m.b.t. 06-09-2018 t/m 07-09-2018
Storm Forecast
Valid: Thu 06 Sep 2018 06:00 to Fri 07 Sep 2018 06:00 UTC
Issued: Thu 06 Sep 2018 04:43
Forecaster: GATZEN
A level 1 was issued across southern France, Alps, western Germany mainly for excessive rain.
DISCUSSION
SYNOPSIS
A strong westerly mid-to-upper-level jet is situated across the Mediterranean that forms a weak ridge between troughs west of Iberia and across Turkey. A vort-max embedded in this flow travels from the Iberian Peninsula to Italy on Thursday, affecting the west Mediterranean during the afternoon and evening. Farther north, weak flow dominates Europe except for an intense cut-off low that moves from Scotland to the North Sea. Some enhanced southerly mid-level winds are also expected at the eastern flank of the southeast-European trough. At lower levels, warm and relatively moist air masses are situated over most of Europe. Colder and drier air spreads from the British Isles towards the Bay of Biscay and into the Benelux countries. Relatively cool air is also present across Scandinavia. A zone with rich humidity extends along the frontal boundary from the Bay of Biscay towards the North Sea and farther into the Baltic States.
Eastern France into Alps and western Germany
A warm and moist air mass is present ahead of the frontal zone from southern France towards to western Alps and farther into western Germany. Some warm air advection is expected while diurnal heating will lead to modest CAPE in the order of 1000 J/kg. Current thinking is that storms form along a convergence line and merge to clusters. Given weak vertical wind shear, severe threat is limited, however, excessive rain is forecast given the slow storm motion and rich moisture. Over north-western Germany and surroundings, vertical wind shear increases in the afternoon. Although low-level cold air advection may already cause decaying storms, there is a weak chance of some better organized updrafts, capable of producing large hail and severe wind gusts. Interaction with the sea-breeze convergence close to the North Sea may even support a tornado given 7 m/s 0-1 km vertical wind shear.
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Verwachtingen/waarschuwingen
