Storm Forecast
Valid: Tue 15 Sep 2026 06:00 to Wed 16 Sep 2026 06:00 UTC
Issued: Mon 14 Sep 2026 12:29
Forecaster: TUSCHY
A level 1 was issued across parts of Belgium/the Netherlands and NW Germany mainly for isolated large hail, gusts and heavy rain.
A level 1 was issued for parts of the S-CNTRL Mediterranean mainly for heavy rain and an isolated tornado.
SYNOPSIS and DISCUSSION
A pronounced wave train affects Europe with a progressive upper trough over NW Europe and a stalling one atop the Ionian Sea. In-between, ridging persists.
ICON EPS/IFS-ENS both show a clustered member cloud of lowered MSLP W/SW of Crete, where 1-3 K positive SST anomalies persist. Limited cooling above keeps diabatic heating in check, so no substantial spin-up of this vortex is forcast. Still, a compact vortex is forecast f.ex. by ICON and healthy rainfall amounts are expected (mostly offshore with 100-200 mm/24h). UK10 has stronger QPF signals over W Crete and if we get the convection more E, some flash flooding is possible. In addition, strong LL shear next to the vortex points to an isolated tornado risk.
Over E Benelux/NW Germany, a classic prefrontal setup evolves, as better BL moisture overlaps with neutral/moist adiabatic mid-level lapse rates. Resulting MUCAPE in the 800-1500 J/kg range overlaps with very favorable kinematics (directional/speed shear), so expect a few initiating supercells especially in the western part of the level 1. Large hail and a few severe gusts are possible. CI over NE Belgium/E Neterlands is still uncertain with not much support by the upper levels (no real IPV signal and only gradually improving upper divergence). Enough signals in latest EPS data for spotty CI during the evening exist for expanding the level 1 that far W however.
Betimes, more CI is forecast deeper into NW/N Germany during the night with improved upper divergence and enough elevated CAPE is present for a few longer-lived mesocyclones shifting E. Despite weak surface gust imprints in NWP data, past events showed that strong dynamic pressure perturbations can support near surface based convection despite some NWP BL stabilization during the evening. Hence despite still isolated large hail and heavy rain, a few strong gusts are forecast. Relaxed 0-1km SRH and rather high LCLs preclude a tornado risk for now.
Despite rather tight clustering of the frontal position in IFS-ENS data, any further de-acceleration could lead to a lowered severe risk with some non-severe nocturnal activity.
