Storm Forecast
Valid: Tue 02 Aug 2011 06:00 to Wed 03 Aug 2011 06:00 UTC
Issued: Mon 01 Aug 2011 17:40
Forecaster: KOROSEC

A level 2 was issued for extreme NE Spain and south-central France mainly for large (a significant event possible), isolated tornadoes, severe winds and excessive convective rainfall.

A level 1 was issued for the rest of France and NE Spain mainly for isolated large hail, intense rain and strong wind gusts.

A level 1 was issued for the eastern Marocco, Algeria into SW Mediterranean mainly for large hail and severe wind gusts.

SYNOPSIS

An omega block pattern establishing across south-central Europe. A dacaying trough/low affecting SE Balkans while a potent upper trough moves across the Bay of Biscay and affects eastern Iberia and France. A surface low moves across France on Tuesday, becoming a focus for active convective day.

The rest of Europe remains under high pressure area centered over Scandinavia. Beneath it, a warm/moist airmass will be locally moderately/strongly unstable but in only weakly sheared environment. Only daytime driven convective storms are expected which could produce an isolated funnel or marginal hail and wind event, but not reaching severe criteria.

DISCUSSION

... France into NE Iberia ...

A potent short-wave trough will be moving from N Iberia across the Bay of Biscay towards UK, pushing an EML into France. A developing SFC low in SW France will favour moisture return into S-CNTRL France which results in moderately instability during the peak heating hours, approx. 1000-1500 J/kg of MLCAPE seem reasonable to become available. With 25 m/s mid-level jet around the base of the trough, around 20 m/s of deep layer shear will become available, overlaping well with the instability. Despite rather strong capping, storms are expected to initiate in the mid afternoon hours and organize into multicells and supercells. Severe wind gust and large to very large hail will be the primary threat. Probabilities for a tornado or two are higher towards the evening when SREH improves across S France. Storms could cluster into a larger system across the central France in the evening hours, trailing NEwards and diminish overnight when instability vanishes.

The surrounding areas under the level 1 could expect more isolated activity with large hail and severe winds within the strongest cells.

... eastern Marocco, Algeria into SW Mediterranean ...

Isolated storms are expected to take place close to the local topography convergence zones in N Africa and shift NEwards towards the evening hours. With rather strong instability and shear in place, severe storms with large hail and damaging winds threat will be possible. If storms cluster into a large system, they will spread/maintain into the SW Meditteranean where models simulate still strong instability.