Analyse
A level 2 was issued in a belt from SE Austria through NE Croatia, E Slovenia and SW Hungary into Serbia mainly for large to very large hail and damaging wind gusts.
A level 1 surrounds the Level 2 for the same hazards but with lesser coverage.
A level 1 was issued from N Romania into Ukraine mainly for large hail and severe wind gusts.
A level 1 was issued across S Norway, S Sweden and from NE Germany to W Poland mainly for tornadoes.
A level 1 was issued across Iberia mainly for heavy rainfall and to the lesser degree for large hail and severe wind gusts.
A level 2 was issued across Algeria mainly for large to very large hail and damaging wind gusts.
A level 1 was issued for parts of Turkey and Caucasus region mainly for heavy rainfall and to the lesser degree for large hail.
DISCUSSION
... NE Italy, S Austria and SW Hungary through Slovenia and Croatia into N Serbia and W Romania ...
A cold front has stalled across the Alps, while to the east cold air wraps around the Alps, creating climatologically notorious situation for severe weather to the southeast of the Alpine range. Along and south/soutwest of the front, specific humidity of around 10 g/kg will overlap with mid-tropospheric lapse rates reaching up to 7.5 K/km, resulting in MLCAPE values between 800 and 1500 J/kg in a belt from NE Italy to Serbia and Romania. Storms will be initiated on the local orography, especially on the southeastern Alps, but also along the cold front itself. The activity will spread southeast and south throughout the day. Isolated cells are forecast at first with some potential for upscale growth in the late afternoon hours perhaps as storms spread towards Serbia and Romania.
Very strongly sheared environment is forecast with 25 to 35 m/s of 0-6 km bulk shear and around 15 m/s of 0-3 km shear. Low-level shear is forecast to be rather weak. Straight to anticyclonically curved hodographs are simulated. Storm splits are expected, but right-movers will be more favoured also thanks to their movement allowing to stay south of the front. Given supercellular convective mode and high LCLs, large to very large hail is expected. Hail sizes greatly exceeding 5 cm will be by rather skinny CAPE profiles above -10 deg C isotherm. Steep low-level lapse rates will favour damaging wind gusts as well and this threat may be greatly increased if an upscale growth into a bow echo can happen. As of writing the forecast, the greatest confidence from the high-resolution models is on the several supercells passing especially in the border region of Slovenia and Hungary and Croatia and Hungary.
High uncertainty exists over W Slovenia and NE Italy, where high-res models are suggesting no convective initiation. However, the profiles don't look too bad over the mountains with no CIN and a moist layer above the LFC. An isolated initiation is thus not ruled out, as suggested by lower resolution models. Given substantial CAPE and shear, large to very large hail and severe wind gusts can be expected with any sustained storms.
... N Romania to Ukraine ...
A rather uncertain forecast concerning the storm intensity over this region. While it is clear that the advancing cold front will be responsible for initiation of scattered storms with some upscale growth into small linear segments possible, there is a large difference in thermodynamic profiles between the models. ICON-EU simulates modest CAPE profiles, but with no significant stable layers, unlike the ECMWF which simulates subsidence between 500 and 600 hPa. Thus, it is possible that storms will remain rather low-topped and will not use moderate to strong deep-layer shear, reaching 15 to 25 m/s in the 0-6 km layer. Despite the uncertainty, Level 1 still seems warranted for isolated large hail and severe wind gusts.
... NE Germany to W Poland and S Norway/S Sweden ...
Slightly enhanced threat of tornadoes will exist over the region with storms developing in low CAPE environment with steep low level lapse rates. While the deep-layer shear will remain mostly below 15 m/s, locally enhanced 0-1 km bulk shear is simulated with values between 10 and 15 m/s in the afternoon hours. Locally, curved hodographs are also simulated with 0-500 m SRH exceeding 100 m2/s2. Should a stronger storm deviate to the right of the mean wind, enough streamwise vorticity may be present in the inflow to support a tornado development.
... Iberia ...
Scattered to widespread storms are expected in weak shear and weak mean wind, resulting in local heavy rainfall threat. Large hail and isolated downbursts may also occur given MLCAPE values > 1000 J/kg and locally high LCLs.
... Morocco to Algeria ...
A short-wave trough is forecast to move across the region throughout the day. Forecast profiles reveal high LCLs, steep low to mid-tropospheric lapse rates, substantial CAPE in the hail growth layer and strong vertical wind shear with hodographs favouring right-moving supercells. Storms will be initiated by orographic lift and will spread eastward with threats of large to very large hail and damaging wind gusts.
... Turkey to Caucasus ...
Within a pool of low geopotential heights, moist profiles with weak mean profiles will result in heavy rainfall threat especially in the areas with complex topography. Towards southeast of the highlighted area, vertical wind shear will be stronger with an attendant increase in the risk of large hail.
Pucik / ESTOFEX
