Storm Forecast
Valid: Wed 22 Nov 2023 06:00 to Thu 23 Nov 2023 06:00 UTC
Issued: Tue 21 Nov 2023 23:36
Forecaster: PUCIK/KUZMENKO

A level 1 was issued across N Algeria and NW Tunisia mainly for heavy rainfall.

A level 1 was issued across S and SE Italy mainly for heavy rainfall and to a lesser extent for tornadoes and marginally large hail.

A level 1 was issued across the extreme S Croatia, W Montenegro, W Albania and W Greece mainly for heavy rainfall.

A level 1 was issued across W Turkey mainly for heavy rainfall and to a lesser degree for tornadoes and marginally large hail.

DISCUSSION

Main focus of thunderstorm activity will be associated with a highly amplified trough stretching from NE Europe towards N Africa. The base of the trough is forecast to detach from the rest as a ridge builds across central Europe. By Thursday morning, the base of the trough will exist as a separate low over northen Africa with easterly component of the flow across the Mediterranean.

Several regions may experience at least isolated severe weather. The first region will be the coastline of Algeria and NW Tunisia, where models simulate numerous waves of showers and thunderstorms throughout the entire forecast period. Forecast profiles reveal low LCLs and majority of CAPE in the warm part of the cloud, suggestive of efficient heavy rainfall processes.

Across Italy, the main period of severe weather activity will begin in the evening hours. It will be connected to the development of the surface low south of Sicily and the establishment of the easterly low-level flow. Heavy rainfall will be the primary threat. Tornadoes will be possible too, especially over Sicily. Their risk will depend also on the degree of cyclogenesis that can be at least partially driven by convection and the subsequent strengthening of low-level flow and low-level shear. For example, ECMWF simulates deeper low and stronger low-level shear over Sicily than ICON-EU with 850 hPa wind reaching up to 20 m/s. Marginally large hail may occur as well with stronger storms with modest CAPE values in the cold part of the cloud.

Across the E coastline of the Adriatic and the Ionian Sea, the highest threat is forecast especially at the beginning of the forecast period as the storms continue their activity from the Tuesday night. Expect heavy rainfall as the primary threat with moist profiles.

Heavy rainfall will also be the primary threat over W Turkey with forecast profiles showing low LCLs and skinny CAPE. Marginally large hail may occur as well, but will be limited by unfavorable CAPE profiles. Tornado risk will be slightly elevated across NW Turkey, where the models simulate curved hodographs with 0-1 km bulk shear over 10 m/s and low LCLs.