CONVECTIVE FORECAST
VALID Thu 17 Nov 06:00 - Fri 18 Nov 06:00 2005 (UTC)
ISSUED: 16 Nov 23:47 (UTC)
FORECASTER: DAHL

There is a moderate risk of severe thunderstorms forecast across the Aegean Sea and W Turkey.

There is a slight risk of severe thunderstorms forecast across the Aegean region surrounding the MDT.

SYNOPSIS

Deep ... stationary synoptic-scale trough is located over NRN and central Europe ... exhibiting several vort maxima at its periphery. Upper cut-off low over the SW Mediterranean as of Wednesday evening is expected to phase with one such vort max and accelerate eastward across the Ionian and Aegean Seas into the eastern Mediterranean. This feature should be focus for organized severe storms on Thursday. At the SFC ... most of Europe is covered by one large low-pressure complex stretching from the S-central Mediterranean up to NW Russia ... promoting SWD advection of deep maritime polar air into central and SRN portions of Europe. This low-pressure system will be modified by regions of weak cyclogenesis over the Gulf of Genoa in the lee of the Alps ... over the Aegean region ahead of the vort max described above ... and over E Europe along main LL baroclinic zone ahead of vort max at the E periphery of the mean trough.

DISCUSSION

...central Mediterranean ... Ionian Sea ... Aegean region...
Plume of unstable boundary-layer air mass ... topped by steep lapse rates associated with an EML from the N Sahara ... combined with mean BL mixing ratios of about 12 g/kg have boosted MLCAPE to 1800 J/kg over the central Mediterranean on Wednesday afternoon (ref. Brindisi 12Z ascent). Though current ... extensive convective activity may be detrimental to early recovery of the air mass ... confidence is reasonably high that MLCAPEs in excess of 1500 J/kg will be available over the Aegean Sea and W Turkey also on Thursday.

Shear profiles should remain conductive to severe evolution with 20+ m/s SWLY 500 hPa flow and about 15 m/s SLY 850 hPa flow. Winds in the BL may additionally back with falling pressures over the Aegean during the afternoon hours. Shear may also be enhanced on the mesoscale near fast vort max crossing the region during the day ... and by topographic features.

Current thinking is that current activity will gradually weaken as it moves inland during Wednesday night ... and that those TSTMS over the SW Mediterranean on Wednesday evening /tied to eastward accelerating upper low/ will undergo substantial strengthening upon interception of moderately unstable air mass over the Ionian/Aegean region late in the day.

Expect upscale evolution into one or more MCS's with imbedded supercells ... posing entire facet of severe convective threats ... including large hail ... damaging winds and possibly a couple of tornadoes.

Activity farther west will likely be less organized given weaker thermodynamic and kinematic fields ... though 500 - 1000 J/kg MLCAPE may be in place as well ... and small hail ... strong wind gusts and possibly a few water spout or two may well occur.

...central Europe...
In the polar air mass over central Europe ... numerous rain/snow/graupel showers will likely occur ... which may account for an isolated CG or two. Thinking is that CG's may be slightly more frequent than on Wednesday ... but still too isolated to warrant a TSTM outlook.

#