Storm Forecast
Valid: Thu 15 Oct 2015 06:00 to Fri 16 Oct 2015 06:00 UTC
Issued: Wed 14 Oct 2015 23:39
Forecaster: GATZEN

A level 2 was issued for southern Italy and the southern Adriatic mainly for excessive precipitation and to a lesser extend large or very large hail, severe wind gusts, and tornadoes.

A level 1 was issued for the central Adriatic mainly for excessive precipitation.

A level 1 was issued for north-east Tunisia mainly for large or very large hail.

SYNOPSIS

High-over-low blocking continues across Europe. On Thursday, the centre of the quasi-stationary cut-off moves from France to northern Italy. A strong jet streak curves around the periphery of this trough. Embedded in this jet, a vort-max travels across Italy to the Balkans on Thursday morning. At lower levels, cold air spreads into the west Mediterranean behind a cold front that moves into southern Italy and the southern Adriatic Sea during the period. Ahead of this cold front, a very moist air mass overlaps with an elevated mixed layer, resulting in high CAPE.

DISCUSSION

Southern Italy to southern Adriatic region

Parallel stratiform MCSs are forecast along the cold front on Thursday morning given the strong flow parallel to the frontal boundary and continuing training storms. Main threat will be excessive precipitation that spreads eastward with the mid-level trough axis in the noon hours. The flow turns southward quickly after the passage of the trough axis as a new vort-max approaches further west. At low levels, the frontal boundary becomes quasi-stationary. Although the flow becomes weaker and low-level moisture decreases, upslope flow will support a continuing risk of severe flash floods across the southern Adriatic region until and beyond the forecast period.

Additionally, strong deep layer bulk shear exceeding 20 m/s is forecast by latest models, and supercells are forecast especially in the southern portions of the cold front. Large or very large hail is forecast especially over southern Italy. Severe wind gusts and tornadoes are not ruled out, although low-level vertical wind shear is limited.