CONVECTIVE FORECAST
VALID 06Z SUN 21/03 - 06Z MON 22/03 2004
ISSUED: 20/03 23:37Z
FORECASTER: DAHL

General thunderstorms are forecast across S Spain.

General thunderstorms are forecast across the British Isles ... N Spain ... W France ... NW BeNeLux.

SYNOPSIS

Amplifying upper pattern present over Europe ... intense digging upper trough is expected to reach W continental Europe by Sunday 06Z ... and to cover all of central Europe towards the end of the FCST period. Main low-level frontal zone ahead of the trough will move SEWD ... and stretch from S Spain across the N Balkan into N Russia by Monday 06Z. SFC low centered over the Skagerrak/Kattegat region on Sunday 06Z ... will move NEWD into the Baltic States during the period.

DISCUSSION

...S Spain...
Very weak lapse rates prevailing across wide regions of S and central Europe E/SE of the main frontal boundary ... however ... GFS simulates weak CAPE over S Spain late in the afternoon. BOLAM also suggests increasing 850 hPa theta-e over S Spain in this time frame. This looks to be associated with an EML advected off the Atlas mountains ... and GFS' CAPE fields appear to be rather realistic. Problematic may be substantial capping beneath the EML ... and rather bad timing of the cold front/DCVA-regime which will affect S Spain late in the night. Nonetheless ... An isolated high-based TSTM or two could form late in the afternoon over S Spain promoted by the orography and/or theta-e advection associated with the EML. Late in the night ... additional TSTMS may develop along the cold front. Shear and CAPE will likely be quite weak ... and organized severe TSTM threat looks to be quite low.

...British Isles ... North Sea ... north-central Europe ... Biscay...
Cellular convection will be present in the deep polar air which is spreading across W and central Europe. Convection should be enhanced ahead of vort max which crosses the Biscay during the day ... and may affect N Spain and W France late in the day. Rather strong shear will likely promote gusty winds with this activity ... but severe threat appears to be rather low.

Daytime heating will likely promote widespread convection over the British Isles and somewhat more shallow convection over west-central Europe ... which may occasionally produce a few lightning strikes. Thermal-trough axis will move across the British Isles into the North Sea ... and bulk activity could be confined to the British Isles and the North Sea.

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