Valid: Thu 02 Oct 2014 06:00 to Fri 03 Oct 2014 06:00 UTC
Issued: Wed 01 Oct 2014 22:02
A level 1 was issued for the south-west Medirterranean mainly for excessive precipitation,
large hail, and to a lower extend tornadoes.
A level 1 was issued for central and southern Italy mainly for excessive precipitation.
Weak mid-level flow affects Europe on Thursday. A remaining of the south-west European trough over the Iberian Peninsula looses its connection to the northern short-wave trough that travels into Italy and the Balkans. Ridges build over France and Germany to Scandinavia as well as from the Aegean to Black Sea region. At lower levels, rather moist air is present over western and central Europe as well as across the Balkans, whereas dry air is affecting most of Scandinavia and eastern Europe. Rich moisture is located over the west Mediterranean. This is also the only region where steep lapse rates overlap with high moisture.
Near the base of the Iberian trough, lapse rates are quite steep as indicated by latest soundings. Additionally, profiles are moist with 0-1 km mixing ratios around 14 g/kg, yielding CAPE in the order of 2000 J/kg. Given north-easterly surface winds and a south-westerly flow above 850 hPa, strong vertical wind shear is expected over the south-western Mediterranean Sea.
Initiation is most likely near the base of the trough, where low-level convergence and weak capping is forecast. These slow-moving storms may produce excessive precipitation and locally large hail. Storms over Spain are expected to spread into the Mediterranean during the night as the trough moves eastward. Given strong vertical wind shear and high CAPE, an MCS is forecast. High precipitation is likely, together with locally large hail. Additionally, tornadoes are not excluded. Flooding will be the main threat along the north Algerian coasts and nearby mountains until the end of the forecast period.
The trough axis of a short-wave trough moves east and crosses Italy on Thursday. Overnights thunderstorms across the Tyrrhenian Sea are forecast to spread onshore across Italy and also over Sardinia and Corsica. Weak lapse rates and vertical wind shear are present, so that well-organized storms are not expected. However, slow storm movement and moist air will allow for excessive precipitation with a threat of local flooding. Storms are forecast to spread south-east during the night hours and may affect the Ionian Sea late in the period.