CONVECTIVE FORECAST
VALID Fri 23 Sep 06:00 - Sat 24 Sep 06:00 2005 (UTC)
ISSUED: 23 Sep 06:01 (UTC)
FORECASTER: DAHL

SYNOPSIS

Rather intense upper frontal zone is extending across the NRN Atlantic across the British Isles and NRN Europe into NW Russia .... with vigorous imbedded trough ATTM just W of the British Isles ... expected to lift NEWD into Scandinavia ... with its SRN portions closing off into a small upper cut-off low over the North Sea early Saturday morning. Farther south ... upper low currently over S Iberia/Morocco is progged to make slow eastward progress ... reaching the SW Mediterranean late in the period. Downstream ... rather extensive but weak upper low persists over the Balkan region ... affecting central and E portions of the Mediterranean. Strong cyclogenesis over the Norwegian Sea is accompanying the Atlantic upper trough ... with the trailing cold front expected to cross the British Isles during the period. Quiescent SFC conditions persisting over central SRN parts of Europe.

DISCUSSION

...central Mediterranean...
TSTMS should continue beneath and S of the central Mediterranean/Balkan upper low throughout the period. CAPEs in the 500 to 1000 J/kg range and rather wak shear in the center of the upper low suggest that organized severe threat is rather low though a few waterspouts may occur given nearly saturated PBLs and little/no capping.

Storms currently failed to develop S of the low's center in DCVA regime ... but expect at least isolated TSTMS to form later today over the Ionian See ... where 15 to 20 m/s deep shear should be realized. These storms may be associated with strong wind gusts and some hail ... maybe achieving severe levels for short periods of time. Thermodynamic fields appear to be too weak for categorical severe ATTM.

...Black-Sea region...
Latest ascents from Samsun (N Turkey) indicate quite moist BL (mean mixing ratio around 14 g/kg) and an EML above it ... yielding afternoon CAPEs in excess of 2000 J/kg. Uncertainty exists on how far NWD and WWD this unstable air mass extends ... but it seems that may have overspread much of the Black Sea and its adjacent coasts. Shear profiles should remain fairly weak ... but the given strong CAPE ... weakly organized multicellular storms with a slight hail/wind threat may form. Uncertainty on coverage and spatial extent of strong thermodynamic fields as well as weak shear preclude a SLGT ATTM.

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