Storm Forecast
Valid: Sat 04 Nov 2006 06:00 to Sun 05 Nov 2006 06:00 UTC
Issued: Fri 03 Nov 2006 23:17
Forecaster: DAHL

SYNOPSIS

Deep and quite intense quasi-stationary upper long-wave trough is extending across eastern Europe and western Russia into the central Mediterranean ... resulting in strong NWLY upper flow with several imbedded short-wave troughs over the North Sea ... S Scandinavia and central Europe. Weak southern upper frontal zone is stretching from the Atlantic eastward across the southern Iberian Peninsula and the NW Maghreb States. At low levels ... extensive high pressure area is sprawling across the central portions of the forecast area ... maintaining strong NWLY SFC flow over central and SE parts of Europe.

DISCUSSION

... Portugal ... SW Spain ...

Weakly unstable and nearly saturated thermodynamic profiles are expected to persist in moist subtropical air mass over the western Iberian Peninsula. Friday's 12Z ascent from Lisboa/Portugal indicated no capping and positive buoyancy close to the ground owing to the saturated boundary layer. This moisture profile should persist as well. Deep shear is progged to decrease somewhat ... remaining marginally supportive of organized convection only over the SW portions of the peninsula where 10 to 15 m/s 500 hPa flow is expected. However ... LLS should be on the order of 10 m/s over much of Iberia ... and coupled with the moist/low-LFC environments this may support a few tornadoes. Highest chance for organized storms ... possibly also containing mesocyclones ... should exist over the SW where DLS will be maximized though a slight tornado threat seems to exist throughout the TSTM area owing to favorable LLS/thermodynamic fields.

... Ionian Sea ... Aegean Sea ...

Strong convective mixing has ensued as the arctic air mass is being advected over the NW Mediterranean Sea. Given SFC dewpoints in the -5 to -10 °C range ... CCL heights are accordingly high. Also ... EL's are expected to remain well below the 500 hPa level. Deepest convection should develop over the Ionian Sea ... and later in the period over the Aegean Sea in association with DCVA-forced ascent. Despite the anticipated shallow nature of the convection ... it has produced considerable amount of lightning over the Mediterranean in similar situations in the past ... which this time is supported by scattered lightning over the N Adriatic Sea on Friday. This convection may be accompanied by strong wind gusts ... which should remain below severe limits though.