CONVECTIVE FORECAST
VALID 06Z SUN 06/06 - 06Z MON 07/06 2004
ISSUED: 05/06 18:05Z
FORECASTER: DAHL

General thunderstorms are forecast across the S UK.

General thunderstorms are forecast across the Iberian Peninsula.

General thunderstorms are forecast across much of E and SE Europe ... and over the central Mediterranean regions.

SYNOPSIS

Band of relatively strong WSWLY upper flow will stretch from the central Atlantic across the N UK and S Scandinavia into NW Russia early Sunday morning. Vort max rounding weakening SE European upper low ... is expected to cross Italy and the Adriatic Sea during the period. Weak ... slowly eastward moving upper trough will affect the W Iberian Peninsula. Main low-level frontal zone is aligned parallel to the upper WSW'lies ... along this boundary ... strong cyclone will persist over and north of N Scandinavia. Plume of high theta-e's is wrapping around weak low-level cyclonic circulation over SE Europe ... mainly affecting Turkey ... the Black Sea and parts of Greece.

DISCUSSION

...Wales ... SW England...
Lowest levels of Brest (N France) and Camborne (S UK) ascents from Saturday 12Z appear to represent the low-level thermodynamic environment that may be present over the S UK on Sunday fairly well ... with low-level dewpoints on the order of 15°C ... and SFC Temps in the low 20s. Assuming slight decrease of 700 hPa temps in the vicinity of approaching upper trough ... minimal CAPE will likely form over the S UK during the day. However ... about 2 K 700 hPa temperature drop predicted by the models ... will likely not be sufficient to uncap the boundary layer. GFS once more offers a very optimistic low-level moisture field ... with SFC dewpoints close to 20°C ... which will likely not be realized. Indications are that an isolated TSTM or two may form towards the afternoon ... primarily over the Cambrian Mountains in Wales and over SW England. Deep-layer shear is progged to be on the order of 15 m/s over Wales ... rapidly decreasing towards the S ... and a few strong wind gusts accompanid by small hail may occur. Low-level flow perturbations over the hilly terrain may promote brief updraft rotation ... posing threat of marginally severe hail. However ... allover severe threat looks to be rather meager given weak thermodynamic fields.

...Italy ... Greece ... Turkey...
TSTMS will likely form ahead of Mediterranean vort max at the W periphery of the SE European upper low. Saturday's soundings show weakly unstable/weakly capped profiles over most of Italy. Given DCVA-related upward vertical motion overspreading Italy during the day and deep-layer shear increasing to 15 to 20 m/s ... a few strong wind gusts and some hail ... both isolated approaching severe levels ... may occur. Though large-scale SRH will not be too impressive ... orographically generated veering profiles may be present locally ... and an isolated rotating updraft or two may occur ... enhancing chances of a few large-hail events.

Downstream over Greece and Turkey ... a few TSTMS will likely form with diurnal heating in weakly capped and weakly unstable environment. Given inverted-V type profiles across much of Turkey ... and deep shear in excess of 20 m/s ... a few marginally severe wind gusts may occur.

...Iberia...
Isolated TSTMS shout initiate towards the afternoon over Spain ... with TSTM coverage possibly being higher than on the previous days given increasing large-scale forcing for upward motion. Expect a few/brief marginally severe straight-line wind events given dry environment/high LCLs ... but coverage of severe TSTM events will likely be rather low.

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