Storm Forecast
Valid: Sat 30 Oct 2010 06:00 to Sun 31 Oct 2010 06:00 UTC
Issued: Fri 29 Oct 2010 22:42
Forecaster: VAN DER VELDE

A level 1 was issued for Spain and Portugal for severe convective wind gusts and a chance of tornadoes.

SYNOPSIS / DISCUSSION

In a western flow over the Atlantic a low pressure system arrives between the British Isles and the Iberian Peninsula. On Sunday it proceeds into the western Mediterranean. A mass of unstable air follows behind the cold front, affecting Portugal and Spain during Saturday evening and night. Inland instability is weaker but may be carried far, especially in association with mid level vorticity maxima. The strong wind field at low levels creates a severe gust potential, while low level shear (0-1 km, 0-3 km) reaches values (15-22 m/s) in support of tornadogenesis. 0-3 km SREH ranges between 200 and 400 m²/s² and also deep layer shear is strong with a maximum of 45 m/s. For this reason, tornadoes seem possible, though the situation is limited by marginal CAPE inland and low shear over sea.
The northwestern Mediterranean Sea could see some thunderstorms belonging to an earlier trough from the Atlantic. Deep layer shear, low level shear and CAPE yield a marginal chance for tornadoes for western Sardinia and Corsica around the early evening.