CONVECTIVE FORECAST - UPDATE
VALID 13Z SUN 27/06 - 06Z MON 28/06 2004
ISSUED: 27/06 13:18Z
FORECASTER: DAHL

There is a slight risk of severe thunderstorms forecast across central France ... N Italy ... Switzerland ... S Germany ... Austria.

General thunderstorms are forecast across the British Islea ... SW and S.central Europe ... E Europe ... Scandinavia.

SYNOPSIS

Refer to the convective outlook from Friday June 27th 13:51Z.

DISCUSSION

...S England...
IR satellite loops as well as model guidance indicate increasingly deep convective mixing in the postfrontal environment over the British Isles ahead of vigorous vort max. This will be aided by solar heating as the convection overspreads the British Isles. Indications are that short convective lines and possibly a few shallow mesocyclones will form given 20 m/s 0-6 km shear in the NRN SEE TEXT area ... increasing to 25+ m/s over S England. Expect a few marginally severe wind/hail events ... but majority of the storms should be non-severe. GFS hints at the possibility of an isolated tornado or two over SE England towards the evening by indicating 0-1 km shear in excess of 10 m/s. Allover severe threat is considered too low for a SLGT ATTM. Activity should weaken late in the night and may spread across the North Sea ... and may graze extreme NW Germany and NW Holland.

...central France ... Switzerland ... S Germany ... Austria ... N Italy...
TSTMS should continue to develop along mesoscale convergence lines apparent on SAT imagery and along orographic features over France ... Switzerland and S Germany ... and later today possibly over N Italy. Degree of CAPE is somewhat uncertain ATTM ... but 500 to 1000 J/kg should be common ... locally maybe somewhat higher ... especially over central France where highest SFC dewpoints are present. Kinematic profiles are favorable for severe evolution with 20 to 25 m/s 0-6 km shear and 100 to 150 m2/s2 0-3 km SRH. Over S Germany and the Alpine regions ... 0-1 km shear is progged reach 10 m/s later today. Any storm in this environment will pose the threat for large hail ... damaging winds ... and especially late this evening over the Alpine regions ... for a few tornadoes.

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