CONVECTIVE FORECAST
VALID 06Z SAT 28/06 - 06Z SUN 29/06 2003
ISSUED: 27/06 19:46Z
FORECASTER: DAHL

There is a slight risk of severe thunderstorms forecast across the Central Mediterranean Regions.

General thunderstorms are forecast across south and central Europe.

General thunderstorms are forecast across eastern Europe.

SYNOPSIS

Omega-type upper flow present over northern parts of Europe ... with a broad rather weak westerly flow covering the southern parts of Europe. Intense vort max is present over the British Isles ... and is expected to slowly progress northwards during the forecast period. Focus for vigorous convective development will be the central and northern Mediterranean regions where ample moisture/instability will be present.

DISCUSSION

...Central Mediterranean...
Friday's 12 Z soundings across the Mediterranean show a variety of severe-weather profiles ... over the northern portions ... strong elevated mixed layer is present atop quite a moist BL ... yielding MLCAPE's in excess of 2500 J/kg. To the south ... low level moisture has been mixed out ... and very steep lapse rates /about 8 to 9 K/km/ are extending as high as 550 hPa. 0-6 km shear is marginal with about 30 knots ... and is not expected to strengthen on Saturday.

Potential problem tomorrow will be the large cap ... especially over S Italy where CINH's of 400 to 500 J/kg are present.

BOLAM's 850 theta-e forecast suggests various mesoscale baroclinic zones across Italy. Also ... outflow boundaries laid out by Friday night's convection as well as the orography will be foci for convective initiation. Weak DCVA is also progged to be present late in the day, which may aid in weakening the cap and allowing more widespread convective development towards the evening.

Expect rapid development of isolated TSTMS during the afternoon primarily over the northern portions of Italy and maybe over Corsica/Sardinia. Shear profiles will be marginal for supecells ... but given the large CAPE and the strong spatial/temporal variability of the low-level wind field ... a fair chance of supercells exists. Expect the whole facet of severe weather ... very large hail ... damaging wind gusts ... flash flooding and isolated tornadoes ... though low-level thermodynamic profiles should not widely be conductive to vigorous low-level rotation ... low-level kinematic and thermodynamic fields are expected be be modified locally by outflow boundaries and by orography though ... yielding large SRH in the inflow and low LCL heights. This coupled with large CAPE densities in the lowest kilometers suggests that a few tornadoes may occur...

An upgrade to MDT may be needed if TSTM coverage becomes larger than currently anticipated.

Farther S over S Italy and the S Balkan ... low-level airmass should suffer from meager moisture and a nearly unpenetrable cap. However ... models suggest that moist advection will take place over S Italy ... the Adriatic and Greece. Have low confidence that this will be sufficient to create a favorable thermodynamic profile ... rather, it is anticipated that inverted-vee type soundings with very large CIN's will be predominant. Present indications are that an isolated short-lived high-based TSTM or two will form over S Italy. Strong downbursts along with some hail will be possible with these cells.

...Eastern Europe...
Shallow TSTMS are expected to develop with diurnal heating over eastern portions of Europe within mixed polar airmass. Given weak CAPE and weak shear ... severe threat will be minimal with this activity.

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