Skywarn Austria Forum

HansSchild hat geschrieben: Aber vielleicht gibt noch der ein oder andere Profi seine Meinung ab ;-

Mesoscale Discussion
Valid: Tue 01 Aug 2017 15:00 to Tue 01 Aug 2017 18:00 UTC
Issued: Tue 01 Aug 2017 15:01
Forecaster: PISTOTNIK

... Switzerland, SW Germany ...

Latest surface observations indicate two boundaries with converging winds which will likely become a focus of convective initiation in the next few hours:

(1) A pronounced dryline has formed along the northern Alpine rim, which separates very moist NE-erly upvalley flow in the forelands from hot and dry S-erly Foehn winds in the Alpine valleys. Latest 14z observations show temperature and dewpoint values of e.g. 28/22°C in Ricken versus 34/10°C in Glarus (E Switzerland), 31/21°C in Feldkirch versus 36/8°C in Bludenz (W Austria), or 29/20°C in Kaufbeuren versus 33/7°C in Reutte (bordering area between Germany and Austria). So far the upvalley flow has been dominant and has "piled" plenty of low-level moisture against the Alps especially in Switzerland, where stations even at an altitude of 800-1000 meters are recording dewpoints around 20°C. This deep moisture likely supports CAPE on the order of 2000 to 3000 J/kg on the moist side of the dryline.
(2) The second boundary is formed by cooler NW-erly outflow winds, which are spreading southward in the wake of an area of clouds, rain and elevated thunderstorms that has moved from E France into W Germany. At 14 UTC, this boundary ran roughly parallel to the dryline and was located about 300 kilometers north of it.

The southern and northern rim of the highlighted area on the map correspond to the 14 UTC positions of the dryline and the outflow boundary, respectively. First storms have recently initiated along both boundaries and are quickly organizing in this environment of high CAPE and ~20 m/s deep-layer shear.
It appears likely that the further increasing mid-level winds will start pushing the dryline northward, while the outflow boundary is proceeding southward, so they may eventually merge and lay out an axis of converging winds and maximized moisture which favourably aligns with the expected storm tracks from SW to NE. It is not ruled out that a large, long-lived storm system with a high-end risk of severe to extreme hail and wind events may materialize and affect N Switzerland and SW Germany in the next few hours.

chris-wels hat geschrieben:Td Salzburg 19°C. ordentlich dampf dahinter. nur wolkenlos, der Deckel ist wie erwartet zu stark. System im Westen ist gewaltig. Solch Dinger sind so ziemlich fies und bringen bei der Schichtung (hohe lapse rate! Scherung!) massive Probleme. Im Unterschied zum 23.7.2009 gabs bei uns in der Höhe auch massive Windgeschwindigkeiten, abseits von Bayern Richtung OÖ ists heute aber ruhiger da ovben. Dennoch nicht zu verachten, der Rest passt sehr gut!Vorläufig bleibt das In der Nacht in BAY draussen, München ist aber höchst gefährdet! und wer weiss...vielleicht setzt eine Zelle den Blinker ud staubt noch OÖ ab. chance dafür gering, aber da. Scherung 0-6km sollte auch zunehmen im NW. na da samma gspannt. Davor heissts nochmal schwitzen und Biergartn aufsuchen.
lg chris

Mesoscale Discussion
Valid: Tue 01 Aug 2017 17:00 to Tue 01 Aug 2017 20:00 UTC
Issued: Tue 01 Aug 2017 17:09
Forecaster: PISTOTNIK/GATZEN

A long wind shift line, interpretable either as a cold front or an outflow boundary, stretches from Lake Constance into SW Poland roughly along the NW-ern border of the highlighted area. Low-level cold air advection, cloudiness and a lack of diurnal heating have strongly reduced the thunderstorm risk anywhere northwest of this line.
Along the boundary, plentiful low-level moisture (2m dewpoints mostly between 16 and 20°C) and steep lapse rates aloft provide CAPE between 1000 and 2000 J/kg, confirmed by 12 UTC soundings. However, there is also a fairly strong cap in place. Best chances for convective initiation in the next few hours exist along the Ore mountains along the German/Czech border, where upslope flow from both sides helps to weaken the cap, and near the German/Polish border, where satellite imagery indicates (struggling) towering cumulus clouds.
If storms form, vertical wind shear is easily strong enough to support supercells with a risk of large hail and severe downbursts. The option of upscale growth into an MCS with a risk of more widespread severe wind gusts is limited by the strength of the cap, and it decreases hour by hour as convective initiation continues to fail.

The severe weather risk is immediately highest in S Germany, where a bowing line with embedded supercells from Switzerland is approaching. This storm system has already produced wind gusts up to 35 m/s and at least golfball-sized hail. It appears likely that it will survive into the Munich area, where 2m dewpoints are still between 17 and 20°C. There is an ongoing risk of severe to extreme wind gusts with the passage of this line, as well as large hail in case of an embedded supercell (especially at its southern end).
Storms will likely weaken after 20 UTC, when they encounter somewhat drier air further east (dewpoints 14-18°C) and nocturnal cooling of the boundary layer sets in.

Bürgler87 hat geschrieben:Druckwelle schiebt jetzt an und formiert eine Squall.
Könnte doch noch spannend werden für OÖ.