CONVECTIVE FORECAST
VALID 06Z SUN 30/11 - 06Z MON 01/12 2003
ISSUED: 29/11 18:56Z
FORECASTER: DAHL

General thunderstorms are forecast across Greece ... extreme western Turkey and the Aegean Sea.

SYNOPSIS

Broad large-scale upper trough is covering the central north Atlantic and parts of NW Europe. Vort max ATTM at its W periphery will dig southeast ... thereby amplifying the mean trough. Associated extensive DCVA will overspread SW Europe during Sunday ... and cause widespread pressure falls across France and Iberia ... models agree in the formation of rather intense SFC low over W France towards the end of and beyond the FCST period. Trailing cold front is expected reach the western Mediterranean Sea early Monday morning. Vort max ATTM at the periphery of the central Mediterranean upper low will intensify slightly while moving SE ... and cover the Aegean Sea and parts of Greece towards the end of this period.

DISCUSSION

...Greece ... Extreme W Turkey ... Aegean Sea...
Soundings from the W periphery of the Aegean Sea reveal nearly neutral lapse rates ... yielding a few 100 J/kg of weakly capped MLCAPE. Ahead of the Mediterranean vort max ... TSTMS will likely develop over Greece during the day and later on over the Aegean Sea. Weak frontal boundary is apparent ahead of the vort max in the 850 hPa theta-e fields and on SAT imagery which will likely be the focus for TSTM development. Storms are expected to continue through Sunday night especially over the Aegean and the coastal regions of Greece and Turkey. Deep-layer shear is expected to be on the order of 30 knots with quite weak low-level shear. PRIND that most of the storms will be rather short-lived ... however ... the warm sea waters and weak low-level shear will likely promote development of a few waterspouts. Also ... storms over the mountainous terrain of Greece could benefit from local low-level flow modifications which may enhance SRH ... and an isolated mesocyclone with a concomitant threat for large hail and maybe a brief tornado cannot be ruled out. However ... allover severe TSTM threat is too low for a SLGT ATTM.

...Iberian Peninsula...
Strong QG forcing for upward vertical motion will overspread Iberia late on Sunday and Sunday night ... The warm-sector airmass is not sampled by radiosonde data yet ... but climatologically this subtropical/Atlantic airmass uses to be quite stable. However ... small sheets of weak instability may be embedded in the airmass ... and a few lightning strikes could occur.

ATTM it does not look that reasonably deep post-frontal cellular convection will affect Portugal and Spain ... though slight changes of the expected CVA/low level temperature advection distribution upstream of the cold front may alter the depth the this convection ... and an update may be needed tomorrow. Will not outlook GEN THUNDER over Iberia ATTM.

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