Storm Forecast
Valid: Thu 26 Nov 2015 06:00 to Fri 27 Nov 2015 06:00 UTC
Issued: Wed 25 Nov 2015 23:01
Forecaster: GATZEN

A level 1 was issued for south-east Italy, the Ionian Sea region, Greece, the Aegean Sea region, and western Turkey mainly for large hail, excessive rain, tornadoes, and severe wind gusts.

SYNOPSIS

A subtropical high is present unseasonably far north to the west of Iberia, pushing the polar jet stream to Iceland where it turns south, forming a deep trough over Europe. A new vort-max ejects into the central Mediterranean on Thursday morning, feeding the trough center that starts to cut off as the Atlantic high ridges into southern Scandinavia. This enables new cyclogenesis across Italy and backing low-level flow further east. As a consequence, relatively rich moisture will be in place from the Ionian Sea to the Aegean, Black Sea and surroundings, whereas dry air has spread into most of Europe.

DISCUSSION

An intense vort-max travels from Sardinia to the Aegean Sea. Downstream, low-level moist air will be advected into the Ionian Sea and Aegean region. Synoptic-scale lift will lead to increasing lapse rates, and CAPE will develop especially ahead of a cold front that moves across Italy at noon, reaching Greece late in the evening. Thunderstorms are forecast especially along this cold front, but further storms may form downstream due to upslope flow (western Turkey, western Greece). Storms that form are expected to become well-organized given moderate to strong vertical wind shear. Latest GFS indicates about 10 to 15 m/s 0-3 km bulk shear. Multicells and supercells are possible, capable of producing large hail and severe wind gusts. Tornadoes are also possible, as well as excessive rain. Overall threat is expected to be of a high-end level 1.