Storm Forecast
Valid: Mon 26 Nov 2018 09:00 to Tue 27 Nov 2018 06:00 UTC
Issued: Mon 26 Nov 2018 08:43
Forecaster: PISTOTNIK

Level 1 areas are issued for S- to W-facing coasts of S Italy, Albania, W Greece and Turkey mainly for flash floods and a lesser degree for tornadoes and severe convective wind gusts.

A level 1 is issued for a sea area S of Sardegna mainly for severe convective wind gusts.

SYNOPSIS

The blocking high over the north Atlantic has weakened considerably, but remains in place. Arctic air gathers beneath an amplifying mid-level trough in northeastern Europe.
The main jet stream is displaced far south and runs across Iberia, the Mediterranean Sea and Turkey, superimposed by numerous short-wave troughs. Near the surface, an elongated low-pressure system has formed along the frontal zone between continental cold air to the north and maritime warm air to the south between Romania and southern France.

DISCUSSION

... Mediterranean region ...

Convective activity will mainly be tied to two features:
(1) A mid-level short-wave trough and an attendant cold front that work their way eastward across The Aegean Sea, Turkey, and the east Mediterranean Sea; and
(2) A particularly strong vorticity maximum that moves from Catalonia (Mon 06 UTC) to the Ionian Sea (Tue 06 UTC) and stimuates the deepening of a new frontal wave along the trailing cold front.
The environment is mainly characterized by a few hundred J/Kg of CAPE, low cloud bases and strong westerly flow (20-25 m/s at 850 hPa), but weaker shear than on on Sunday due to advection of cooler air and widespread previous convective overturning. The main risk with scattered, partly embedded thunderstorms is heavy rain along west-facing coasts, namely Calabria, Albania, W Greece and W Turkey, as well as Sardegna as the new cyclone approaches. The same applies to southern Turkey, where the weaker onshore and upslope winds are offset by more CAPE (up to 700 J/kg). If frictional convergence near the coasts enhances low-level shear, isolated tornadoes or severe wind gusts are not ruled out, though storm organization is not too likely.

Severe wind gusts will become widespread under tightening pressure gradients at the rear (southwest) flank of the second cyclone over the west Mediterranean Sea as the day proceeds, but most of the CAPE will be consumed by then and deep convection should not be involved anymore. However, the strengthening wind field is predicted to overlap with CAPE by some hundred kilometers in a region south of Sardegna around evening, and a level 1 is issued for a risk of severe wind gusts with a convective component.