22-04-2018 00:00 | Estofex | m.b.t. 22-04-2018 t/m 23-04-2018
Storm Forecast
Valid: Sun 22 Apr 2018 06:00 to Mon 23 Apr 2018 06:00 UTC
Issued: Sat 21 Apr 2018 21:32
Forecaster: TUSCHY
Numerous level 1s were issued for isolated large hail and severe wind gusts (Spain/E-Netherlands/N-Germany), isolated large hail (N-France) and heavy rain (Alps).
SYNOPSIS
Progressive sinusoidal ridge/trough pattern affects N-Europe. Zonally oriented high over CNTRL Europe weakens as a whole during the forecast but re-strengthens a bit from Germany to CNTRL-Sweden during the day in the shape of a northward building rige, as a negatively tilted trough over NW-Europe approaches with WAA from the W. A deamplifying lead short wave crosses Benelux/N-Germany during the forecast while moving through that ridge and dissolving during the night.
Omega-like blocking pattern persists over the Mediterranean as an upper low over Sicily will drift leisurely east and as a strong upper vortex SW of Portugal remains in place.
DISCUSSION
... W-/CNTRL-Europe ...
Three foci for CI exist:
a) Leading/dissolving short-wave crosses Benelux/N-Germany during the day. Temporarily cooling mid-levels atop moderate BL moisture (Tds around 10C and recovering 0-1km mixing ratios of 8-9 g/kg) support thinning tongue of somewhat steeper mid-level lapse rates. Forcing emerges from that wave but also from an organizing warm front, which should run from the North Sea to Saxony around noon and moves E/NE thereafter. CAMs agree in active CI especially over NW-Germany as warm sector should stay avoid of thick clouds (despite debris cirrus from overnight convection)- either forced by the wave or the orography towards CNTRL-Germany. 15-20 m/s DLS with rather straight hodographs support splitting and rapidly clustering multicells with large hail and heavy rain - temporal updraft rotation in initially discrete storms is possible. Forecast soundings reveal inverted-V structure in the lower troposphere and hence the risk of conglomerating cold pools with cold pool driven/bowing lines of DMC and a temporal/regional risk of strong to severe wind gusts exists. However, weak low-tropospheric background flow should keep this risk in check. The activity weakens after sunset over NE/E-Germany.
b) Approaching negative tilted trough pushes a cold front S/E over CNTRL-France and W-Germany. Mostly separated CAPE/shear fields limit the risk to isolated large hail during initiation in the French level 1 area. During night, BL cooling/vanishing CAPE assist in elevated/embedded sub-severe thunderstorms wich move into SW/W/CNTRL-Germany.
c) Lowering heights and strong diabatic heating with ongoing unusual warmth result in diurnal driven active mountain convection along the Alps. Slow moving storms pose an heavy rainfall/large amount of small hail risk and a small level 1 was added. Again, activity weakens beyond sunset.
(Alleen de voor NL en direct aangrenzende gebieden relevante tekstdelen zijn overgenomen, klik hier voor de volledige forecast, red.)
Hagel(-schade) | Verwachtingen/waarschuwingen | Wind/storm (-schade)
