CONVECTIVE FORECAST
VALID Mon 21 Nov 06:00 - Tue 22 Nov 06:00 2005 (UTC)
ISSUED: 20 Nov 16:38 (UTC)
FORECASTER: GROENEMEIJER

SYNOPSIS

Monday at 06 UTC... the 500 hPa flow across Europe is very much blocked with a cut-off low centered over the Balkans and a large high-pressure system over the British Isles. An inverted trough initially extending northward from the Balkan low centre over the eastern Europe and the Baltic States, swings rapidly westward and then southward, and is expected over the Alps around 00Z. A low pressure area to the west of the Iberian Peninsula initially moves a little eastward.

DISCUSSION

...southern and southeastern Spain, western and southern Portugal...
On the southeastern flank of the aformentioned low pressure area... unstable air flows towards the Iberian Peninsula. Scattered storms within this air-mass should generally be non-severe, although some isolated stronger multicellular storms should be possible. Isolated large hail may occur. Given the expected large low-level buoyancies across (the seas adjacent to) southern Portugal and Spain, it is not ruled out that an isolated waterspout or weak tornado forms.

...Italy, Tyrrhenean, Adriatic and Ionean Seas...
A diffuse baroclinic zone across the area separates cold air over the Balkans and central Europe and warmer air over the western Mediterranean Sea. As large-scale rising motions and low-level convergence affects the area... the baroclinic zone is expected to intensify during the second half of the period... and a frontal zone should form stretching from the northern Tyrrheanean to the southern Adriatic. About 20 m/s of 0-6 km shear is generally present in the area. The rising motions go hand in hand with destabilisation, that will likely result in the formation of low amounts of poorly-capped CAPE over the indicated maritime areas. Scattered thunderstorms are expected to form there. As instability will likely remain (very) weak, the threat of severe weather should be low.

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