Storm Forecast
Valid: Fri 15 Dec 2023 06:00 to Sat 16 Dec 2023 06:00 UTC
Issued: Thu 14 Dec 2023 23:41
Forecaster: KUZMENKO/PUCIK

A level 1 was issued over Greece and NW Turkey mainly for large to very large hail, heavy rainfall and to a lesser degree for tornadoes

DISCUSSION

... Greece and NW Turkey ...

At 300 hPa, a jet stream with wind speed of up to 50 m/s is simulated at the forward flank of a deep trough and will overspread the area during the forecast period. The trough is forecast to slowly approach the area during the day. Closer to the surface, a surface low will reside over the Agean Sea during the forecast period, with strong convergence zones along its warm and cold fronts. The warm front is forecast to stagnate across N Greece/NW Turkey, resulting in multiple rounds of storms and an enhanced possibility of significant rainfall amounts and flash flooding.

All models seem to be in an agreement that the formation of storms in the area can be expected already in the morning hours close to the frontal boundaries. Within the warm sector, the convective initiation might be limited by a layer of drier air around 700 hPa. As the synoptic-scale lift overspread the area, the storms will spread S and E during the day.

Given strong vertical wind shear with 0-6 km shear values being over 20 m/s, well-organised storms, including supercells are forecast. With CAPE values reaching 1000 J/kg and strongest buoyancy located in the cold part of the cloud, multiple storms will be capable of large hail. Very large hail may occur as well in supercells, even though the chances are lowered to some degree by modest MLCAPE values.

North of the warm front, where the thermodynamic profiles are moister and the CAPE profiles are skinnier, effective heavy rainfall processes can also be expected. Here, the threat of large hail will be lower.

Some of the coastline areas of Turkey and Greece show rather curved hodographs with SRH values in the lowest 500 m above 100 m2/s2, suggesting a threat of tornadoes. However, the extent of the overlap of enhanced SRH and SBCAPE is rather limited and differs among the models. Thus, this threat is more questionable. Very strong low-level shear is simulated to the N of the warm front. However, the storms will be elevated here, effectively reducing the tornado chances to 0.