Storm Forecast
Valid: Thu 19 Sep 2013 06:00 to Fri 20 Sep 2013 06:00 UTC
Issued: Wed 18 Sep 2013 22:26
Forecaster: GATZEN

SYNOPSIS

A large trough extends from west of Scandinavia into central and eastern Europe. A strong mid-level jet stream is present from the British Isles to the Alps and further to the Black Sea. Several short-wave troughs travel eastward into south-east Europe during the forecast period. Convective activity is limited by the weak low-level moisture across most of Europe. Steeper lapse rates can be found below the cold mid-level trough centers. Over northern Africa, another short-wave trough moves eastward across Tunisia.

DISCUSSION

Denmark and surroundings

A few waterspouts may form in the morning hours near the center of them mid-level trough. Lapse rates will be steep due to cold air and the rather warm sea surface, while the vertical wind shear is expected to be weak initially. Later in the period, chances of waterspouts decrease as vertical wind shear will increase from the west.

Northern Balkans to Black Sea

At the base of the European trough, a strong vort-max will move eastward on Thursday. It will provide strong QG forcing. At the surface, a tongue of moist air will spread east ahead of a cold front. Although moisture and lapse rates are rather weak, an overlap with weak CAPE is expected ahead of the cold front. Thunderstorms are forecast to spread east during the day. These storms may be rather intense given the strong vertical wind shear in excess of 15 m/s in the lowest 3 km. However, severe potential is limited due to the weak CAPE. A few severe wind reports may occur. Near the Black Sea, storm coverage will likely increase as low-level moisture will be higher there. Across the Black Sea, storms will likely go on through-out the night.

Tunisia

Thunderstorms are expected to affect northern Tunisia on Thursday. Ahead of the approaching short-wave trough, a surface low will slowly move east across northern central Tunisia. With easterly surface winds, a moist maritime air mass will spread into the area. Over northern Tunisia, lapse rates will be rather poor, and CAPE will be weak, bit embedded thunderstorms are expected due to the strong forcing. While the area of strong vertical wind shear will be located to the south of the forecast domain, a threat level is not issued. However, a few hail events are not ruled out. Additionally, excessive precipitation is possible.