CONVECTIVE FORECAST
VALID 06Z WED 20/10 - 06Z THU 21/10 2004
ISSUED: 19/10 23:46Z
FORECASTER: GROENEMEIJER

General thunderstorms are forecast across southern Ireland, much of England, the Low Countries, northwestern and western Germany, France and much of the Iberian peninsula and the western Alps.

SYNOPSIS

Wednesday at 06Z... a north-south oriented ridge is located from Scandinavia to Italy. Downstream of the ridge, a low pressure system is located over northwestern Russia and moving southward. The main area of interest this period is western Europe, where a southwesterly mid and upper-level flow is located. The jet corresponds with a broad baroclinic zone in the lower troposphere.

DISCUSSION

...Spain, France, England, Benelux, western Germany ...
Within the baroclinic zone, two cold fronts are forecast. One is stretching from southeastern England to western Spain Wednesday at 06Z. The second front is located over the eastern Atlantic. A warm front over northern France is expected to move northward. The air-mass that is advected northward over France is expected to be neutral to slightly latently unstable. A few convective storms are expected within the warm sector as well as near the various frontal systems. Strong low-level helicity is expected near the warm front and in the warm sector that moves northward during the morning and afternoon over northern France, the Benelux countries and western Germany. Helicity will also be high across southern England near the associated occlusion. A few storms may develop mesocyclones and produce strong to severe gusts and tornadoes. This may also occur over western and central parts of France and much of Spain and Portugal, where low-level shear is forecast to be high as well and scattered convective storms are forecast. The second front will pose a similar threat as it passes southern England and western France during the evening and the Low Countries after midnight. It is hard to indicate which areas will have a higher threat of seeing severe weather than others. Have chosen to include most of the aformentioned areas in the slight risk at this time.

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