CONVECTIVE FORECAST
VALID 06Z SAT 10/01 - 06Z SUN 11/01 2004
ISSUED: 09/01 18:55Z
FORECASTER: DAHL

General thunderstorms are forecast across south-central Mediterranean Sea ... Greece and W Turkey.

SYNOPSIS

Amplitude of intense upper flow regime is expected to increase during the period ... with the SW European upper ridge FCST to build northwards ahead of the rapidly wesward- moving digging upper trough at the moment S of Greenland. Large SFC low over the N Atlantic will be reinforced as waves develop at the periphery of the upper trough. Fast vort max will be present over the Adriatic Sea at the beginning of the FCST period ... and promote cyclogenesis over the S Adriatic ... resultant SFC low is expected to deepen quickly and to be centered over the E Aegean Sea/SW Turkey by the end of the FCST period.

DISCUSSION

...Mediterranean...
Air mass which will be involved in the warm sector of the developing cyclone ... is currently lying over the west/central Mediterranean Sea ... and radiosonde data suggest that it is fairly stable ... and only slowly moistened by the Mediterranean Sea. GFS assumes the low-level WAA to be sufficient to destabilize the air mass over the S Adriatic ... the Ionian and S Aegean Sea during Friday night and Saturday ... yielding weakly unstable profiles. It appears that Q-vector convergence will be maximized along strengthening warm front stretching across N Greece and the Aegean Sea into SW Turkey N of the low center ... and elevated TSTMS may develop along and N of the warm front ... especially late in the day/evening. Further convective development is expected along the cold front ... this activity will likely benefit from quite strong shear ... with 60+ knots mid-level jet overspreading the region late in the day/evening. Isallobaric flow along with low-level WAA ahead of the front ... and increasing low-level flow (40+ knots at 850 hPa per MM5 12Z solution) will likely promote favorable kinematic environment for a few rotating updrafts. GME's solution hints at some uncertainty regarding this scenario as substantially weaker cyclogenesis/low-level wind fields are offered by the 12Z solution. Nonetheless ... slight threat for short-line segmts/bow echoes and for a few supercells exists ... capable of producing severe straight-line winds ... marginally severe hail and maybe even a brief tornado or two.

Uncertainty with this scenario ... and generally marginal thermodynamic setup precludes categorical risk at the moment ... but an upgrade to SLGT may be necessary if thermodynamic fields improve more than currently expected.

...NW British Isles...
Cold front associated with strong Atlantic low will cross the British Isles late Saturday night with cellular convection likely being present in its wake. However ... it appears that lack of DCVA in the wake of the front and strong low-level CAA will limit convective threat.

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