Storm Forecast
Valid: Tue 07 Mar 2017 06:00 to Wed 08 Mar 2017 06:00 UTC
Issued: Mon 06 Mar 2017 23:33
Forecaster: DAFIS

A level 2 was issued for SE Greece and SW Turkey mainly for excessive precipitation, large amounts of small hail, severe wind gusts and tornadoes.

A level 1 was issued for S Italy, Albania, Greece and Turkey mainly for excessive precipitation and severe wind gusts.

SYNOPSIS

A large mid/upper-air trough extends from NE Atlantic all the way down to central Mediterranean basin, and an embedded short-wave trough over NW Italy is progressively moving SE, over the Mediterranean Sea, where we expect to separate from the mean flow and become a large cold pool. This cold bubble will be the steering mechanism of a low level cyclonic vortex, currently located in N Italy. This cyclone (National Observatory of Greece named it "Galateia") is expected to deepen the following hours and high resolution NWP models based on ECMWF, forecast a center of 993 hPa on Tuesday.

As far as the rest of the european domain is concerned, A rsidge is forming in the western parts and another short-wave troufg travels north from central Europe, towards Poland and Belarus, providing some lift, resulting in some pulsating storms.


DISCUSSION

.... S Italy, Albania Greece, Turkey ....

Ongoing DMC activity over Italy will continue to produce clusters of storms further south untill the early morning hours of Tuesday. Locally severe wind gusts are expected in S Italy.

As the short-wave trough approaches from the north and the cyclone deepens further while moving over the Mediterranean Sea, a dry intrusion is expected to attain a S-to-N axis towards Greece between 18z and 00z. This intrusion is characterized by a strong vorticity lobe and providing the presence of moist-unstable air masses below, instability can be enhanced in an extent that NWP models cannot currently forecast accurately. Current thinking based on GFS is that if LL convergence lines exist in S Greece in the afternoon hours, a line of multicells can form entering the Aegean Sea during the night. High values of DLS overlap with some hundreds of MLCAPE (20 m/s and up to 800 J/kg respectively). These storms are not expected to attain large amounts of helicity, before reaching the level 2 area on the map, so the main threat is only excessive precipitation, locally large amounts of small hail and some severe wind gusts (in the level 1 area). ECWF shows a more conservative scenario, without CI over this area (around Attica).

Later during the night, as this convergence zone is moving east, SE Aegean Sea seems to have better mixing ratio values to increase the effective PW up to 20-25 mm. Even though DLS is only locally exceeding 10-15 m/s, 0-3km directional shear overlaps with 1300 J/kg MLCAPE according to latest GFS output. Multicells or a supercell can form during the early morning hours of Wednesday, increasing the threat of any kind, including tornadoes. The coasts of Turkey will have the greatest threat of excessive precipitation as the plume of moist air masses will probably lock to the steep orography and could induce flash floods.