Storm Forecast
Valid: Sat 10 Nov 2007 10:00 to Sun 11 Nov 2007 06:00 UTC
Issued: Sat 10 Nov 2007 10:42
Forecaster: DAHL

SYNOPSIS

Deep and intense upper long-wave trough, exhibiting several vort maxima at its western and southern periphery, is present over central portions of Europe. The southern vort max is supporting strong cyclogenesis over the Aegean region which will spread northeastwards across the Black Sea into the southern Ukraine until Sunday early morning. The perturbations at the W periphery of the large-scale trough will induce more or less well-defined wave cyclones affecting a region including the northern North Sea, the British Isles, France, Benelux, and W Germany. At this time, it does not appear that these features will be accompanied by appreciable deep convective activity.

DISCUSSION

... Aegean region ... south-central Mediterranean ...

Convection is increasing over the N Aegean along the cold front of an intensifying SFC low. The 00Z ascents from the Aegean region don't look particularly exciting, but GFS suggests that increasingly steep mid-level lapse rates are being advected into the region from the central Balkans, which should increase the instability in the Aegean pre-frontal air mass.

Although CAPE should remain somewhat marginal -- despite the improving lapse rates -- increasing large- and mesoscale upward vertical motion as well as increasing shear should maintain some threat for severe storms. It seems that highest probabilities will exist between early afternoon and late evening, whereafter more stable/dry air will be advected into the pre-frontal region over Turkey.

Given strong low-level and deep-layer shear, supercells, capable of large hail, severe wind gusts, as well as tornadoes, are anticipated. Frictionally-enhanced SRH over extreme west Turkey and over the isles will place these locations in the area most favorable for tornadoes.

... Baltic Sea ... N Poland ...

Sporadic lightning could accompany comparatively shallow convection beneath an upper-cold pool over the Baltic Sea ... but lightning frequency should be too insignificant to warrant a thunderstorm outlook.

... Adriatic Sea ...

Quite a deep dry-adiabatically mixed boundary layer has developed over the northern Adriatic Sea, drawing attention to a potential waterspout threat. However, it seems that the air will remain too dry to support significant moist convection. Moisture advection that is expected to occur late Saturday night will increase the chance for isolated lightning over the E Adriatic Sea, but the low-level lapse rates should have decreades by then, so that the allover waterspout threat should be limited today/tonight.