CONVECTIVE FORECAST
VALID 06Z SAT 28/08 - 06Z SUN 29/08 2004
ISSUED: 27/08 21:11Z
FORECASTER: DAHL

There is a slight risk of severe thunderstorms forecast across W Turkey ... W Black Sea ... E Romanina ... Moldavia ... central Ukraine.

General thunderstorms are forecast across E Spain ... SE and E Europe ... central Scandinavia.

SYNOPSIS

Intense upper low analyzed over the N North Sea on Friday evening ... is progged to lift NEWD across Scandinavia during the FCST period ... with upstream trough digging SE ... approaching the N British Isles late in the period ... altogether resulting in a broad long-wave trough at midlevels by Sunday 06Z ... covering N and parts of central Europe. Upper low over the S Balkans is expected to move east ... covering the Black Sea by Sunday morning. At low levels ... wavy frontal boundary is expected to stall over central Europe ... stretching from central France into NE Europe. Plume of moist/unstable air will likely persist ahead of the SE European upper low.

DISCUSSION

...W Turkey ... W Black Sea ... E Romanina ... Moldavia ... central Ukraine...
TSTMS should (re-)develop early in the day at the E periphery of the Balkan upper low ahead of small embedded vor max. Friday's soundings from this air mass reveal MLCAPEs ranging from 800 to 1100 J/kg. Expect these values to prevail on Saturday as well ... probably with some variation in low-level moisture profiles/LCL heights.

Best shear profiles are advertised to exist over N Turkey ... the E Black Sea ... SE Romania and the S-central Ukraine ... with deep shear in the 15 to 20 m/s range ... decreasing during the day. 0-3 SRH of 150+ J/kg will likely be present over SE Romania and the S-central Ukraine ... associated with WAA as high theta-e's wrap around the low center.

TSTMS may tend to be slightly elevated in WAA regime ... but enough SFC-based CAPE is expected to be in place for convection to root down into the boundary layer.

Expect a few rotating updrafts with a threat for large hail and damaging winds ... and possibly a tornado or two especially over SE Romania and the S-central Ukraine where low-level shear should be best. Severe TSTM threat should decrease farther N with weakening shear profiles.

...Scandinavia...
Scattered ... shallow showers and probably isolated TSTMS should form ahead of and underneath lifting trough over Scandinavia ... about 15 m/s deep-layer shear will be in place per GFS 12Z ... but shallow nature of the TSTMS as well as minimal CAPE should limit severe threat. Will place a TSTM area near the thermal-trough axis where convection should be deepest.

...E Spain ...
A few high-based TSTMS may form over E Spain late in the afternoon in weakly unstable environment. Dry/deep CBL should favor strong outflow winds ... which may briefly approach severe levels. Anticipated isolated nature of the storms and allover marginal setup preclude categorical risk ATTM.

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