Storm Forecast
Valid: Sat 29 Sep 2018 06:00 to Sun 30 Sep 2018 06:00 UTC
Issued: Fri 28 Sep 2018 22:03
Forecaster: PUCIK

A level 2 has been issued for the southern Ionian Sea, Crete, southern / southeastern Greece and the Aegean Sea mainly for extremely heavy rainfall, tornadoes and severe wind gusts.

***For detailed information on the track and intensity of synoptic-scale wind field of the 2018M02 system, please refer to specialized product (Mesoscale discussion)***

SYNOPSIS

An extensive high pressure system centered over the British Isles dictates the weather pattern over Europe. On its forward flank, northerly flow advects relatively cool and dry airmass over much of Central and Eastern Europe, resulting in conditions too hostile for DMC. Active pattern will continue over Scandinavia where weakly electrified DMC may occur along the Norwegian coastline in the environment of steep mid-tropospheric lapse rates.

Focus of the the DMC activity will be a warm core, slightly asymmetric cyclone that will move from the Ionian Sea, across the S Peloponnese peninsula towards the Aegean Sea and W Turkey, embedded in WSW to SW-ly flow of broader trough covering the area.

Isolated to scattered DMC may also occur over the Pyrenees, on the southern flank of the cut-off low over S France that will slowly shift SW-wards. Later in the night, isolated thunderstorms are forecast to start forming S of the Massif Central.

DISCUSSION

... Ionian Sea, S Greece, Aegean Sea, W Turkey ...

Scattered to widespread DMC is forecast along the track of the cyclone as it moves ENE-ward during the day. Most of the convection will be confined to the eastern and northeastern sector of the low, where upward synoptic-scale motion combines with advection of moister airmass from S. Forecast soundings suggest skinny CAPE profiles with very low LCLs and high RH throughout most of the troposphere. Such profiles, combined with strong, 20+ m/s, lower tropospheric flow impinging on the steep coastlines of Greece and Turkey will create very dangerous conditions regarding extreme rainfall. Effective, warm-rain processes will promote rain intensities of 100 mm/h upward. While NWP differs in the exact location of the highest rainfall sums, it is likely that several locations, especially over SE and E Peloponnese, will see rainfall accumulations of 200 to 300 mm, depending on whether and where rain bands become quasi-stationary, resulting in cell training. The threat of long-lasting rain bands is somewhat mitigated by rather quick movement of the low eastward.

Besides the heavy rainfall risk, tornadoes will be possible in the northeastern sector of the surface low, where strong LLS and curved hodographs suggest that low-level rotation may develop within the stronger cells.

Individual cells and their downdrafts may also locally slightly enhance the severe wind gusts beyond the background synoptic-scale wind field that is discussed in detail in a special product issued for the cyclone. Severe winds solely induced by the synoptic-scale wind field of the low are not considered in this forecast.