Storm Forecast
Valid: Wed 10 Jul 2024 06:00 to Thu 11 Jul 2024 06:00 UTC
Issued: Tue 09 Jul 2024 22:08
Forecaster: PUCIK/ENGERT
A level 2 was issued across SE Germany, N/NW Austria, Czechia, extreme E Germany and W Poland mainly for very heavy rainfall, large hail and severe wind gusts.
A level 1 surrounds the level 2 for the same hazards.
A level 1 was issued for E France, Switzerland, NW Italy mainly for large hail and severe wind gusts.
A level 1 was issued across S Sweden mainly for heavy rainfall and to the lesser extent for marginally large hail, severe gusts or tornadoes.
A level 1 was issued for Turkey for large hail and severe wind gusts.
A level 1 was issued across NE Ukraine and extreme W Russia mainly for heavy rainfall and large hail.
DISCUSSION
... SE Germany, NW Austria, Czechia, extreme E Germany, W Poland ...
High MLCAPE values ranging from 2 to 3 kJ/kg are forecast in a combination of mixing ratios exceeding 14 g/kg and 6.5 to 7 K/km lapse rates. Fat CAPE profiles are obvious from the forecast Skew-Ts with LCLs from 1 to 1.5 km. Scattered to widespread storms will form along the convergence zone and nearby the local orography in the afternoon hours. Storms will predominantly organize into multicell clusters given 0-3/0-6 km bulk shear around 10 m/s. Transient supercells will be possible if storms trigger over boundaries and/or near the local orography, where the shear can be enhanced. This pertains especially the N Alpine forelands.
Heavy rainfall will be the primary risk. Extreme rainfall intensities are forecast given high CAPE, high moisture content and also locally deep warm cloud depth. It's likely that 1h rainfall accumulations reach 50 - 100 mm in the most affected locations. Large hail is likely as well given the fat CAPE profiles and abundant CAPE above -10 deg C isotherm. The threat of very large hail (> 5 cm) is conditional upon the supercell occurrence. Given prolific precipitation loading of updrafts, wet downbursts are likely as well. A level 2 seems well warranted for the area. A level 1 directly surrounds the level 2 for the same hazards, but lesser areal coverage.
... E France to N Italy and Switzerland ...
A mix of multicells and supercells is possible in the 0-6 km bulk shear ranging from 15 to 25 m/s. The coverage of storms will be less than further E and with lesser CAPE, resulting in less overall heavy rainfall threat. Severe wind gusts and large hail will still be possible. Very large hail threat will be limited in supercells by a combination of skinnier CAPE profiles and dry/stable layer beginning at 500 hPa.
... Sweden ...
A fast moving cold front will initiate widespread convective storms. Ahead of the front, southerly 15 - 20 m/s flow at 850 hPa is forecast. With a mixing ratio of 10-12 g/kg, CAPE values of 500-1000 J/kg are forecast. Given widespread initiation and 0-3 km bulk shear of around 15 m/s, the environment will support linear segments along the front. The type of predominant severe weather threat depends on whether convection will be elevated or surface-based. Most models suggest elevated storms, while ICON-EU shows abundant SBCAPE. With elevated storms, the main hazard will be heavy rainfall or marginally large hail. Surface based storms will have higher chance of severe wind gusts. The threat of tornadoes is suggested by the ICON-EU model simulating surface-based storms (the main source of uncertainty in this forecast) in low LCLs and lovely curved hodographs showing helicity of up to 200 m2/s2 in 0-1 km depth. Ahead of the cold front, in the warm air sector, isolated thunderstorms may develop mainly in Blekinge and Kalmar County leading possibly to large amounts of precipitation.
... Turkey to Caucasus ...
High-based storms are forecast to form with inverted-V profiles and much of CAPE being above -10 deg C isotherm. Expect large hail and severe wind gusts with stronger storms. Over Caucasus, there will also be threat of heavy rainfall.
... NE Ukraine to extreme E Russia ...
Slow moving storms with threat of heavy rainfall are forecast. The stronger storms will be capable of large hail given fat CAPE profiles.
