CONVECTIVE FORECAST
VALID 06Z SUN 19/12 - 06Z MON 20/12 2004
ISSUED: 18/12 19:10Z
FORECASTER: DAHL

General thunderstorms are forecast across the Ionian and Aegean Sea ... as well as over the eastern Mediterranean Sea.

SYNOPSIS

Broad and rather strong upper westerly flow is present over western ... central and southern Europe ... with several vort maxima imbedded. Large-scale ridge is covering parts of E Europe and W Russia. Main features this period will be upper low expected over Greece by the beginning of the period ... which is progged to weaken and accelerate east ... and fast upstream vort max which should cross France and reach the central Mediterranean towards Monday morning. Seasonably strong SFC low is accompanying this feature... and should reach N Italy towards Sunday afternoon.

DISCUSSION

...Ionian and Aegean Sea...
Weak CAPE should persist beneath and ahead of Aegean upper low ... with quite weak lapse rates but relatively moist boundary layers ... supporting low LCL heights. At the periphery of the low-level cyclone ... up to 25 m/s wind speeds are simulated at 850 hPa across the Ionian Sea into E Turkey. 500 hPa flow should be on the order of 15 to 20 m/s ... but it looks that most favorable shear profiles will remain outside convectively mixed region. Nonetheless ... a few severe wind gusts and a tornado or two should be possible ... especially over extreme W Turkey and S of the Ionian Sea where wind field are expected to be strongest.

...NW Mediterranean...
Convective scenario associated with vigorous upstream system is rather uncertain ... GFS12Z and NMM00Z both produce weak CAPE in the warm-sector air mass of the low shifting into the N Mediterranean during the day. This could be a result of overdone model moisture flux from the sea into the boundary layer ... but it could also be realistic ... as the increase of CAPE seems to coincide with increasing UVVs/upper-level cooling late in the day over the central and N Mediterranean ahead of vort max. If storms do form ... a few severe wind gusts as well as a tornado or two could occur given the strong wind fields ... but uncertainty concerning the evolution of CAPE precludes categorical risk ATTM.

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