Forecast Update
Valid: Wed 21 Oct 2009 12:00 to Thu 22 Oct 2009 06:00 UTC
Issued: Wed 21 Oct 2009 12:07
Forecaster: PUCIK

A level 1 was issued for Portugal and Spain mainly for severe wind gusts and tornadoes.

A level 2 was issued for Southern France mainly for excessive precipitation.

A level 1 was issued for Northwestern Italy mainly for excessive precipitation and to the lesser extent for tornadoes.

A level 1 was issued for Western Italy and Corsica mainly for tornadoes and to the lesser extent for severe wind gusts.


SYNOPSIS

Refer to the convective outlook.

DISCUSSION

... Portugal, Spain...

Level 1 is enlarged and shifted over much of the Iberian penninsula. Models now point to the scenario of a marginal instability belt ahead of the rapidly moving cold front and very strong environmental wind shear, with values over 15 m/s in 0-1 km. Strong synoptic-scale forcing will support generation of a strongly forced convective line with threat of severe wind gusts, as windspeeds at 850 hPa level will reach more than 25 m/s. At the same time, SREH values over 400 J/kg, low LCLs and very high LLS point to the risk of tornadoes, in case that embedded circulations develop within the line.

... Southern France...

Level 2 is issued for the area, where several models produce very high precipitation amounts, possibly locally exceeding 100 mm/24 hours. Persistent convergence of the unstable airmass and strong low level flow pointing into this region support the regeneration of the thunderstorms and " cell training pattern" is quite possible. Therefore, marginal Level 2 is introduced for this region.


...Corsica...

Corsica was included in the Level 1 due to the threat of tornadoes with strong low level shear forecat by models ( over 10 m/s), low LCLs and enhanced SREH values. Marginally severe wind gusts might occur with rapidly moving thunderstorms as well.