CONVECTIVE FORECAST
VALID Fri 30 Dec 06:00 - Sat 31 Dec 06:00 2005 (UTC)
ISSUED: 29 Dec 16:37 (UTC)
FORECASTER: TUSCHY

There is a slight risk of severe thunderstorms forecast across western Turkey

Thunderstorms are forecast across Ireland and parts of Great Britain

Thunderstorms are forecast across Adriatic Sea

SYNOPSIS

Long wave trough, which was placed over central Europe and which was filled with a very cold airmass, seems to get splitted by another strong low pressure area, situated south of Iceland.... The result will be 2 cold core centers // the first one over Norway, moving northward....the second one over Austria and reaching SE-ward, sliding eastward slowly //, which will affect the northern and southern parts of Europe...The other system, S of Iceland, will bring unsettled conditions for Ireland and United Kingdom...Most parts of the Mediterranean and NE Europe will see stable conditions under strong ridging.

DISCUSSION

...western Turkey...
Well developed upper-level trough, filled with very cold mid-/upper-level airmass, will move eastward during the next 24 hours...Downstream LL depression, which developed yesterday over southern Italy, will race northward pretty fast...Models agree in broad area with low pressure over Greece and western Turkey... Departing LL depression will help a cold front to move eastward over Greece during the morning hours, then slowing down significantly east of Greece due to near parallel alignment in respect to the background flow... The risk area will also see enhanced UL divergence values ( LE region of impressive subtropical jet ( 150kt + in H2 ), coming out of cntrl Africa and right entrance region of a departing polar jet, downstream of the UL trough )....Current thinking is that TSTMS will ongoing over Greece, moving eastward along the cold front... This system will also be the focus for continuing new storm development.... Up to 200 J/kg SBCAPE possible in the risk area .... Main threat will be severe wind gust reports ( due to strong H85 wind in excess of 20m/s and steep LL lape rates )...don't want to exclude one or two tornado reports along the coastal areas, because of enhanced LL shear ( up to 12m/s ).

...Ireland and parts of Great Britain...
Main focus for isolated TSTM development will be ESE-ward racing cold front... Prefrontal warm front sector will be characterized by a pretty warm and humid airmass... Current thinking is, that the warm front sector will be well capped ( strong WAA in the mid-leves and pretty poor chances for some insolation due to a thick cloud shield ), so only expect an isolated elevated TSTM along the cold front with a severe wind gust threat ( impressive mid-/ and LL jet present ).
Next focus for isolated TSTMs will be a short wave, reaching Ireland during the night hours.... Strong LL shear and steep lapse rates will be conducive for a few severe wind gust reports but GFS brought the strongest winds in H85 southward with each run, so there will be some uncertainness, how widespread severe wind gusts can develop over Ireland ATM.

Cold front will also reach the coastal areas of northern Portugal, Spain and France... Limited instability present, so only expect isolated to scattered TSTM development ( mainly over N-Spain/Portugal)...Again, main threat will be a few severe wind gust reports.

...Adriatic Sea ...
Very cold H5 air (-35°C ) will cross the northern and central Adriatic Sea...SST will be in the range of about 15°C and this will be enough for some instability release (GFS up to 300 J/kg SBCAPE )... Conditions look favorable for a few waterspout reports along the coastal areas.

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