CONVECTIVE FORECAST
VALID 06Z SAT 20/09 - 06Z SUN 21/09 2003
ISSUED: 19/09 18:19Z
FORECASTER: DAHL

General thunderstorms are forecast across NE Europe and NW Russia.

General thunderstorms are forecast across W Iberia and the Biscay.

General thunderstorms are forecast across the south-central Mediterranean.

SYNOPSIS

Strong zonal upper frontal zone is extending from the North Atlantic across north Scandinavia into NW Russia. Vigorous embedded vort max will cross the Baltic States and NW Russia on Saturday. Vort max ATTM W of the british Isles ... will make little ESEWD progress per GFS/GME 12Z and meso ETA 00Z runs. Upper low ATTM off the Iberian W coast ... is expected to make slow northeastward progress but to remain off-shore during the period. Synoptically quiescent conditions prevailing over SRN and central parts of Europe beneath large/weak upper ridge.

DISCUSSION

...NE Europe ... NW Russia...
Ahead of vigorous vort max over NW Russia ... a few rather shallow TSTMS may develop during the day. CAPE is expected to be very meager ... but shear will likely be around 70+ knots in the lowest 6 km ... and short line segments ... briefly capable of producing strong/severe wind gusts may occur. However ... poor thermodynamic support is limiting organized severe thunderstorm threat ATTM.

...Iberia ... Biscay...
A few TSTMS have formed over the E Atlantic off the Iberian coast ... apparently along cold frontal boundary associated with the upper low. Thermodynamic properties of the involved subtropic/Atlantic airmass are not sampled by radiosonde network ... but presence of TSTMS shows that at least minimal CAPE is present. This activity may affect W Iberia on Saturday ... though model guidance suggests that maximum QG forcing for UVM will remain over the Ocean. Also ... BL airmass over S Iberia is expected to become increasinly capped as EML from the Atlas advects north during the day.

...Mediterranean...
Ill defined vort maxima are evident on WV imagery over the Mediterranean ... which will likely support a few small cumulonimbi in weakly stable/weakly capped airmass again. Severe threat is negligible with this activity.

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