Storm Forecast
Valid: Fri 28 Jul 2023 06:00 to Sat 29 Jul 2023 06:00 UTC
Issued: Thu 27 Jul 2023 20:49
Forecaster: PUCIK
A level 2 was issued across S Russia mainly for large to very large hail and heavy rainfall.
A level 2 was issued across S and SE Ukraine mainly for very heavy rainfall and to the lesser degree for large hail.
A level 2 was issued across N Russia mainly for tornadoes, severe wind gusts and to the lesser degree for large hail.
A level 1 was issued across SE France for large hail.
A level 1 was issued across Poland for marginally severe wind gusts.
SYNOPSIS
A complex synoptic-scale pattern is forecast across Europe with rather low-amplitude flow across much of Europe with the exception of the E part. At mid to upper troposphere, a large cyclone will reside over Scandinavia. One of its short-waves will cross Poland during the day, another one will eject from Belarus to NE across Russia. A cut-off low will develop over S Russia, its trough rotating from the Black Sea towards Caucasus. A pronounced frontal boundary will run from Caucasus towards S Russia and further N with two separate low pressure centers near the surface. Severe storms will be concentrated especially along this front.
DISCUSSION
... S Russia ...
Widespread storms are expected to form in the afternoon hours as the short-wave trough moves over the region and storms initiate rapidly on the mountains, spreading NE-wards. Forecast profiles show substantial CAPE below -10 deg C and 15 - 20 m/s of 0-6 km bulk shear, allowing at least for transient supercells with large to even very large hail. As the storm coverage increases and shear decreases towards the evening, heavy rainfall will occur as well.
... S/SE Ukraine ...
Strong isentropic lift is forecast on the warm wave of the boundary north of the deepening surface low. As the easterly flow increases to N of the low, widespread storms will form along the front with threat of very heavy rainfall and perhaps large hail on the eastern flank of the Lvl 2 where higher CAPE is forecast.
... N Russia ...
A pronounced warm front will lift across the area. Along and slightly N of it, all models agree on a belt of strongly curved hodographs with 10 - 15 m/s of 0-1 km bulk shear and over 100 m2/s2 of SRH in the 0-500 m layer combined with low LCLs and potential for surface-based storms. This would imply risk of even strong tornadoes. ECMWF is most aggresive with storms along the warm front, while ICON keeps storms more confined to the cold front or to the N/NW of the boundary, where they would be elevated. Nevertheless, Lvl 2 seems to be warranted and the situation needs to be closely monitored. Besides tornadoes, damaging wind gusts may become an issue if storms move towards warm sector with higher LCLs and 0-3 km bulk shear of around 20 m/s. Large hail can be expected along the cold front with more linear hodographs in case that supercells form. However, it should be lesser threat compared to tornadoes or wind gusts.
... SE France ...
A marginal and questionable Lvl 1 is issued for a chance of large hail if some sustained updrafts develop in the environment of 15 - 20 m/s.
... Poland ...
A marginal lvl 1 issued for marginally severe wind gusts in the environment of skinny CAPE and straight hodographs with up to 15 m/s of 0-3 km shear and mean flow between 15 and 20 m/s. In some models, the CAPE may be too marginal to sustain enough latent heat release to support development of more substantial linear segments. Nevertheless, a low probability of this threat exists.
