Storm Forecast
Valid: Tue 03 Oct 2023 06:00 to Wed 04 Oct 2023 06:00 UTC
Issued: Mon 02 Oct 2023 22:24
Forecaster: PUCIK/KUZMENKO
A level 2 was issued across NE Germany and W Poland mainly for severe wind gusts and to the lesser degree for tornadoes.
A level 1 was issued across Germany, W Czechia and W Poland mainly for severe wind gusts and to the lesser degree for tornadoes.
A level 1 was issued across E France and SW Switzerland mainly for large hail.
A level 1 was issued across the E Black Sea mainly for heavy rainfall.
A level 1 was issued across SE Turkey, NE Syria, N Iraq, Armenia, Azerbaijan mainly for severe wind gusts, heavy rainfall and to the lesser degree for large hail.
DISCUSSION
... Germany, W Czechia, W Poland ...
At mid to upper troposphere, a sharp short-wave trough is forecast to cross the area in the wake of a surface cold front. Q-vector convergence forecast shows an area of synoptic-scale ascent at the mid-troposphere over the descent in the lower troposphere owing to the already ongoing cold air advection behind the front. Despite that, models show the development of broken band of storms in the belt of enhanced low-level moisture. CAPE profiles will be rather skinny and storms low-topped with EL mostly below or around 6 km. Forecast hodographs show strong unidirectional shear and strong mean flow in the bottom 1 - 3 km. 0-1 km bulk shear will locally exceed 15 m/s as the 850 hPa flow approaches 25 m/s. A mix of fast-moving linear segments and supercells is forecast. Combination of strong low-level shear and well-mixed boundary layer ahead of the storms will result in severe wind gusts being the primary threat. Tornadoes may occur with supercells, but the risk will be reduced by relatively high LCLs and a lack of streamwise vorticity in the inflow to the storms.
A level 2 is issued for the corridor with the highest probability of the severe wind gusts and high vorticity in the storms according to the high resolution, convection allowing models.
... E France, SW Switzerland ...
A marginal Lvl 1 is issued for an isolated large hail given higher CAPE values compared to the areas further N. 0-6 km bulk shear will be strong enough to sustain well-organised multicells and at least transient supercells. The coverage of storms will quickly decrease towards SW.
... S Sweden, S Finland, Estonia, W and N Latvia ...
A warm front is forecast to lift across the area. Strong warm air advection regime will result in a large shield of stratiform rainfall with embedded convection. The convection will be only weakly electrified, if at all, given skinny CAPE profiles and rather low ELs. Strongly curved hodographs are forecast N of the warm front with substantial values of SRH. That said, storms will most likely remain elevated due to the stable boundary layer, reducing the risk of tornadoes and/or severe wind gusts by significant margin. Both threats will be possible in case that surface-based storm manages to develop along or S of the warm front. This eventuality needs to be monitored throughout the day.
... E Black Sea ...
A trough is forecast to cross the area, providing the synoptic-scale lift. Ongoing moist onshore flow will result in numerous rounds of storms and subsequent threat of high rainfall accumulations, especially in the areas with orography.
... SE Turkey, N Syria, Armenia, Azerbaijan ...
Isolated to scattered storms are forecast throughout the day. In the morning, lower LCLs are forecast with higher RH throughout the troposphere and relatively weak mean flow, yielding some flash flood risk. In the second part of the day, 0-6 km bulk shear is forecast to increase, locally reaching or exceeding 15 m/s. Combined with relatively high LCLs and CAPE confined especially to the cold part of the cloud, large hail may occur with transient supercells. Near the southern edge of the Lvl 1, Inverted-V profiles are simulated, suggesting a threat of downbursts.
