Storm Forecast
Valid: Mon 08 Oct 2007 06:00 to Tue 09 Oct 2007 06:00 UTC
Issued: Mon 08 Oct 2007 06:28
Forecaster: DAHL

SYNOPSIS

Rather intense upper trough located over Scandinavia at the beginning of the period will merge with a downstream upper low centered over E Belarus/N Ukraine. Another, small but vigorous upper cut-off cyclone is simulated to eject from a large-scale Atlantic upper low, and to reach the northern British Isles late in the period.
Over the Mediterranean/S Europe ... two weak upper troughs/lows are remaining in place, both of them making only slow eastward progress. One of these features will slowly drop southward from northern Spain/NW Mediterranean Sea, while the other one will linger over the Ionian Sea region. At low levels ... strong/large low-pressure complexes are present over the N Atlantic as well as over NE Europe, while rather quiescent conditions prevail elsewhere.

DISCUSSION

... Ionian Sea region ...

Based on the latest rawinsonde data, it appears that CAPE has largely waned in the plume of warm/moist air accompanying the E periphery of the upper trough over the Ionian Sea. However, GFS still simulates quite ample CAPE, and it is well possible that this is realized in a narrow, unsampled region.
It seems that a mid-level wind band of 15 to 20 m/s will develop S and E of this upper low ... weakening late in the evening.
It is anticipated that storm organization will increase during the day, with upscale growth into one or more MCSs being possible. Primary mode should be well-organized multicells as well as isolated mesocyclones, with a threat for severe wind gusts, large hail, and maybe also a few isolated/brief tornadoes, though low-level shear looks to remain quite weak. By the time LLS does increase per GFS, the deep shear should have weakened already, to that allover degree of storm organization should be limited. Still, an isolated tornado cannot be discouted.

... western Mediterranean region ...

Weak CAPE is likely to persist ahead of the upper trough that moves across the northwestern Mediterranean regions today. It seems that 20 m/s DLS will develop over the extreme SW portions of the Mediterranean, but storm coverage is simulated to be rather low there. Still, a few cells could develop and produce marginally severe wind/hail. Since GFS shows no QPF signals over the favorably sheared regions, will not introduce a categorical risk at this time.

... northern Baltic Sea ... Baltic States ...

Comparatively shallow convection will likely develop underneath the NE European upper low. Though shear will be moderately strong, shallow nature of convection and limited low-level mesoscale forcing for ascent beneath the core of he upper low should limit severe threat. Storms may even fail to be significantly electrified, so will not issue a thunderstorm area for this area.