CONVECTIVE FORECAST
VALID 06Z SUN 05/09 - 06Z MON 06/09 2004
ISSUED: 04/09 18:55Z
FORECASTER: DAHL

There is a slight risk of severe thunderstorms forecast across Spain and the SW Mediterranean Sea.

General thunderstorms are forecast across SW Europe ... SE Europe ... and the central Mediterranean Regions.

SYNOPSIS

Omega-type upper flow pattern is expected on Sunday ... with an upper high over central Europe ... an upper low anchored over the Iberian W coast ... and a broad/weak quasi-stationary upper trough covering E Europe and the central Mediterranean regions. Intense Atlantic zonal upper frontal zone is FCST to spread eastwards across NRN portions of Europe. At the SFC ... majority of Europe is affected by extensive SFC high pressure area ... with weak SFC lows persisting over Iberia and the SE Mediterranean regions respectively.

DISCUSSION

...Spain...
Strong thermodynamic profiles should persist over E Spain and the SW Mediterranean Sea. MESO ETA as well as GFS 12Z hint at development of a severe MCS late Saturday night which would affect convective environment on Sunday ... mainly by providing outflow boundaries and impeding insolation. However ... indications are that 1500+ J/kg MLCAPE should be common late in the afternoon.

Like on Saturday ... lack of strong large-scale upward motion and the presence of a strong cap may again prove obstructive to convective development. GFS and GME advertise patches of weak DCVA overspreading the region during the day ... but confidence that widespread TSTMS initiate remains somewhat limited ATTM.

If convection develops ... deep-layer shear of about 20 m/s should support supercellular storms ... capable of producing large hail and damaging wind gusts. Low-level shear is progged to weaken during the day with 0-1 km shear below 10 m/s and 0-1 km SRH on the order of 50 m2/s2 during the early afternoon and evening hours.

Though CAPE should decrease towards NW Spain ... kinematic environment should still be supportive to severe TSTMS with large hail and damagning winds being the main threats.

...S France...
BOLAM indicates strong 850 hPa theta-e advection over S France towards the afternoon and during the evening/night ... which may promote a few TSTMS. Though shear is expected to be quite weak ... a few wind/hail events approaching severe levels may occur late in the afternoon given anticpiated strong thermodynamic fields.

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