CONVECTIVE FORECAST
VALID 06Z THU 16/10 - 06Z FRI 17/10 2003
ISSUED: 15/10 22:23Z
FORECASTER: DAHL

There is a slight risk of severe thunderstorms forecast across the Ionian Sea ... Greece ... and the W Aegean Sea.

General thunderstorms are forecast across Iberia and the southwestern and central Mediterranean Sea.

SYNOPSIS

Block pattern is persisting through the forecast period ... with an extensive quasi-stationary upper high covering NW and central Europe. Closed upper low ATTM approaching Iberia is progged to make little eastward progress and become stationary over the peninsula. Vort max ATTM over the Baltic Sea ... will move southwards at the eastern periphery of the upper ridge and reach the central Balkan Stated towards the end of the FCST period. At the SFC ... dominant feature will be extensive high pressure system extending across major parts of the forecast area. Weak pressure falls are expected beneath/ahead of the Iberian upper low. Focus for convective development will once more be the Mediterranean and the Iberian Peninsula. Weakly unstable airmass currently present over the central Mediterranean and Iberia will spread as far east as into the Aegean Sea on Thursday.

DISCUSSION

...W Mediterranean Sea ... Greece ... Aegean Sea...
Convection should redevelop in response to low-level warm advection and weak DCVA over the Ionian Sea ... the S Balkan and the W Aegean Sea during the day ... and possibly also farther west and northwest along and south of 850 hPa theta-e gradient stretching across the NW Mediterranean.

Deep-layer shear across the Ionian Sea ... the S Balkan and the Aegean Sea will likely be on the order of 40 knots ... and meso ETA as well as GFS suggest SRH at or above 150 J/kg across this region. Though CAPE will likely be rather meager ... a few rotating updrafts capable of producing large hail may be possible. Dewpoint depressions in the boundary layer of only a few Kelvin along with expected low level kinematic setup indicate that supercells have fair chances of becoming tornadic. Activity farther W and NW should pose less of a severe threat given weaker kinematic support.

...Iberia...
Expect scattered TSTMS to develop during the day over the Iberian Peninsula. Setup is quite marginal ... CAPE will likely be very weak and expected large-scale deep-layer shear of about 30 to 40 knots will likely not promote severe evolution. However ... at the periphery of embedded small-scale vort maxima ... deep-layer shear may be somewhat augmented. Also ... the complex terrain over Spain/Portugal will likely promote regions of locally enhanced SRH ... and if a few cells happen to form in such an environment ... a few large-hail events could occur. Also a tornado or two would be possible then. However ... this scenario is quite conditional and the majority of the storms will likely be sub-severe ... and a SLGT is not necessary ATTM.

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