Storm Forecast
Valid: Thu 10 Oct 2019 06:00 to Fri 11 Oct 2019 06:00 UTC
Issued: Wed 09 Oct 2019 23:20
Forecaster: GATZEN

A level 1 was issued for the Ionian Sea mainly for excessive precipitation and waterspouts.

A level 1 was issued for the south-east Mediterranean mainly for large hail, severe wind gusts, tornadoes, and excessive precipitation.

A level 1 was issued for southern Belgium, Luxembourg, eastern France, southern Germany into western Czechia and Austria mainly for severe wind gusts and tornadoes.

SYNOPSIS

A weak cut-off low slowly migrates east across the south Mediterranean. A high pressure area located across north-western Africa ridges into western Europe. A downstream trough migrates across Central Europe. It is associated with a weakening upper-level front.

Southern Ionian Sea towards southern Greece

An elevated mixed layer is advected towards the Aegean Sea in a broad warm air advection regime ahead of the approaching cut-off trough. Rich low-level moisture is forecast that overlaps with steep lapse rates across most of the warm air advection regime. High CAPE around 2000 J/kg is expected. Large CIN present south of Greece will weaken during the period, and thunderstorms that are initially forecast across the Ionian Sea are expected to spread east.

Storms over the Ionian will form in weak vertical wind shear in moist profiles and with low cloud bases. Clusters of storms will cause excessive precipitation and waterspouts. Farther east, a low-level jet is forecast to develop between the cooler air across the Ionian Sea and the elevated mixed layer to the east. Strong 0-3 km vertical shear of 15 m/s will favor storm organization. Given straight hodographs expected by latest model output, splitting storms and multicells are forecast that can form bowing lines later on. Large hail and severe wind gusts are forecast, and excessive rain is also possible. Weak low-level shear and some CIN limit the potential of tornadoes. However, a brief event is not ruled out.

Southern Belgium, Luxembourg, eastern France, southern Germany into western Czechia and Austria

An upper-level front is located at the flanks of a trough that migrates east on Thursday. Low-level stretching and some diabatic heating are forecast and steep low-level lapse rates are expected in a moist air mass. Some low-based CAPE is forecast and storms will move east in the morning along a surface cold front. In the wake of the cold front, some isolated showers and thunderstorms are expected. With high equilibrium level temperatures around -15 degree Celsius, only intense storms may produce some lightning. However, with strong vertical wind shear and long, curved hodographs, any isolated storms that forms can form a mesocyclone. Additionally, bowing lines of storms can develop along the cold front. Low cloud bases are in place and a few tornadoes are forecast. Tornado potential is forecast to shift east in the afternoon and will weaken in the evening. Furthermore, locally, severe wind gusts are expected, in particular with bowing lines. Excessive precipitation and marginally severe hail is not ruled out. Overall severe risk is of low-end level 1.