Storm Forecast
Valid: Thu 04 Sep 2014 06:00 to Fri 05 Sep 2014 06:00 UTC
Issued: Wed 03 Sep 2014 22:07
Forecaster: GATZEN

A level 1 was issued for the Aegean region, Italy, and the Balkans mainly for waterspouts and excessive rain.

A level 1 was issued for north-eastern Spain mainly for severe wind gusts and large hail.

SYNOPSIS

A broad high is centred across the Baltic States, and rather dry air advects from Russia south-east into the northern Black Sea as well as in the North Sea region. At its southern flank, a cut-off low affects the Balkans and north Mediterranean. A plume of warm and moist air spreads westward at the northern flank of this trough into the Alpine region. Warm air is also present over Iberia and Turkey. The best low-level moisture is located over the western and eastern portions of the Mediterranean as well as over the southern Black Sea.

DISCUSSION

Balkans, Adriatic Sea, and Italy

The cut-off low will stay over the Aegean area on Thursday. Rich low-level moisture is present over the Sea, overlapping with steep lapse rates due to rather cool mid-level air masses. Storms are forecast especially in the night and morning hours along the land-sea-breeze convergence. During the daytime, moisture and convergence will move onshore, where storms are forecast especially in the afternoon and evening.

Weak vertical wind shear is forecast, and storm organization will be weak. Main threat will be waterspouts and excessive rain.

Northern Spain

Rich moisture across the Mediterranean continues to advect onshore below an elevated mixed layer over Iberia. On Thursday, the strong capping inversion is expected to erode due to an approaching short-wave trough and strong diurnal heating. Over the mountains, thunderstorms are quite likely in the afternoon. These may become quite well-organized as vertical wind shear near the base of the short-wave trough is expected to increase to 15 m/s, and multi- or even supercells may be capable of producing large hail. The main threat will be dry downbursts given inverted-v profiles over Iberia.

Turkey

Mid-level warm air advection sets in as the Mediterranean trough slightly turns westward. This mid-level warming will limit the potential of storms on Thursday. Nevertheless, rich moisture over the southern Black Sea region may lead to some onshore storms during the day, capable of producing local flash floods.