Storm Forecast
Valid: Sat 15 May 2021 06:00 to Sun 16 May 2021 06:00 UTC
Issued: Fri 14 May 2021 21:59
Forecaster: PUCIK
A level 2 was issued across Russia mainly for large to very large hail, damaging wind gusts and to the lesser extent for tornadoes.
A level 1 was issued across western Russia, Belarus, Latvia, Estonia and southern Finland mainly for excessive rainfall.
A level 1 was issued across northern Germany mainly for excessive rainfall.
A level 1 was issued across western Greece / Albania mainly for excesssive rainfall and to the lesser degree for severe wind gusts and tornadoes.
SYNOPSIS
At mid to upper troposphere, strong zonal flow is forecast in between of high geopotentials over the southwestern Mediterranean and a low over the British Isles. Towards the east, situation becomes more complicated with a number of separate short-wave troughs embedded in a large pool of low geopotentials that separates a ridge over northern Scandinavia from a ridge over the Middle East and Caucasus. A sharp short-wave is forecast to cross the Ionian Sea during the forecast period and move over the Aegean Sea into northwestern Turkey. Towards the north, a short-wave will cross northern Germany and another one will cross southern Scandinavia, both moving northwards. The fourth short-wave will translate from eastern Ukraine into Russia.
Closer to the surface, a pronounced frontal boundary is simulated over Russia with majority of Europe remaining under cool and rather moist airmass. Combination of modest moisture and lapse rates around 6.5 K/km will allow for widespread marginal CAPE across Europe and half of the continent may see isolated to scattered convective storms. More widespread storms are forecast over the eastern Ionian Sea, over northern Germany and over Russia.
DISCUSSION
... Russia ...
Synoptic-scale lift is forecast to overspread the warm sector in the early afternoon hours. Warm sector will involve mixing ratios above 10 g/kg and lapse rates in between of 6.5 and 7 K/km. The strongest lift and highest coverage is forecast over the northwestern part of the Level 2, while storms may exist in more isolated mode near the southern edge of the highlighted area, where higher CIN values are anticipated. In general, environment will be characterised by moderate to high MLCAPE values between 1 and 2.5 kJ/kg and 0-6 km bulk shear ranging from 15 to 25 m/s, suggesting moderate to high potential for severe and well-organised convection given the successfull initiation.
Storms will initiate along and ahead of the advancing cold front, which does not show significant convergence along it. This may preclude rapid storm clustering in the early stages of initiation. Initiating storms will eventually form a mixed mode of isolated supercells and QLCS with perhaps one or more bow-echoes (given 0-3 km bulk shear exceeding 15 m/s). Straight and long hodographs will favor large to very large hail and damaging wind gusts over tornadoes. Tornadoes will be most likely in the evening hours near the northern edge of the Level 2 as the low level shear ramps up. Storm will spread towards northeast during the forecast period and will likely persist well into the overnight hours.
... Western Russia into Estonia ...
Slowly moving thunderstorms capable of localized heavy rainfall events are forecast over this area given the mean wind below 5 m/s, low LCLs and high RH throughout the whole troposphere.
... Northern Germany ...
Similarly to the Level 1 area to the east, moist profiles with low LCLs are forecast over this domain, promoting high precipitation efficiency. Scattered to widespread initiation is likely in the afternoon hours and storms will spread from south to north in the mean wind of around 10 m/s. Moderate degree of mean wind may limit the heavy rainfall threat to some degree, but the overall risk seems still high enough to warrant a low-end Lvl 1.
... Western Greece, Albania ...
Widespread storms are forecast ahead of the sharp short-wave trough that will cross the area in the morning hours. Over the northern part of the Lvl 1, excessive rain will be primary risk with moist profiles and slow storm motion. Towards the south, 0-3 km bulk shear will rapidly increasing, reaching over 20 m/s over southern Greece. Here, storms will pose risk of severe wind gusts and despite relatively straight hodographs, a tornado can not be ruled out either.
