Storm Forecast
Valid: Thu 17 Apr 2014 06:00 to Fri 18 Apr 2014 06:00 UTC
Issued: Wed 16 Apr 2014 22:20
Forecaster: GATZEN

A level 1 was issued for south-western Turkey mainly for excessive precipitation.

SYNOPSIS

An intense cut-off trough will develop until the forecast period that affects the central and east Mediterranean. Warm air masses will be present to the east and north-east of the trough, whereas cold air currently over central Europe will spread into the central Mediterranean. Warm air and ridging dominates across south-western Europe. A sharp trough will enter the North Sea on Thursday evening.

DISCUSSION

Aegean Sea and surroundings

A southerly flow will affect the Aegean Sea on Thursday, associated with 0-1 km mixing ratios around 8 g/kg just east of an approaching cold front. Ahead of this slow-moving frontal system, the moisture will be advected into western Turkey and Bulgaria. Weak CAPE will develop during the period across the Aegean region and Bulgaria due to rather stable lapse rates over the cool sea surface. This will allow for thunderstorms ahead of the cold front that may become better organized in the afternoon hours due to increasing vertical wind shear in the range of a southerly low-level jet. Linear organized storms are expected across the Aegean and south-western Turkey with a threat of excessive precipitation due to the slow movement of the frontal system that lasts until the morning hours. Due to the weak instability, severe potential is expected to be limited, but a tornado is not ruled out across western Turkey where low-level vertical wind shear may reach 10 m/s in the lowest km.

Additional storms are expected further north over Bulgaria and surroundings during peak heating. Despite limited CAPE, moderate vertical wind shear around 10 m/s in the lowest 3 km may support a few mesocyclones and multicells, capable of producing isolated large hail and strong wind gusts. However, the overall threat seems to be too weak for a level 1. This activity will rapidly decay after sunset.

Iberian Peninsula

A relatively moist low-level air mass becomes unstable due to steep lapse rates and diurnal heating. Large scale support and vertical wind shear remain weak. However, given a deep well-mixed boundary-layer in the noon and afternoon, an isolated dry microburst is not ruled out. Additionally, stronger storms may produce marginally severe hail.