Storm Forecast
Valid: Sun 25 Nov 2007 14:00 to Mon 26 Nov 2007 06:00 UTC
Issued: Sun 25 Nov 2007 13:40
Forecaster: DAHL

SYNOPSIS

Strongly meandering, intense upper westerly flow is present over the north Atlantic and Europe ... with an amplifying long-wave trough over central Europe spreading into the Balkans through the remainder of this period. A quasi-stationary upper low resides over the NW Maghreb States, maintaining also a low-level cyclonic circulation, which acts to advect steep mid-level lapse rates across the central Mediterranean. The central-European upper trough is accompanied by an intense/large surface low pressure system which is covering the North Sea, Scandinavia and NE Europe. While also spreading southeastwards, this feature will undergo slight weakening until early Monday morning.

DISCUSSION

... southwestern and central Mediterranean ...

Focus for potentially severe convection exists over the western and central Mediterranean regions east of the N-African upper low, as well as ahead of the central-European upper trough which should graze the Adriatic Sea late on Sunday. CAPE does not appear to be too impressive, though 00Z soundings as well as numerical guidance suggest that a Saharan EML is being advected atop the central Mediterranean, so that maybe MLCAPEs is excess of 1000 J/kg could occur. Deep shear is expected to remain above 20 m/s, locally/temporarily even as high as 35 m/s. Low-level shear/SRH are simulated to exceed 12 m/s / 400 m2 s-2 over the south-central and southwestern Mediterranean, spreading across the Ionian Sea into Greece during the evening and night.

This suggests that storms will have the potential of becoming supercellular, with a particular threat for tornadoes, along with large hail and strong wind gusts. The most favorable kinematic environment will move northeastwards during the period, but bulk of convective activity is simulated to remain anchored more over the southwestern Mediterranean, and slightly outside the region of best kinematics. However, at least isolated storms will likely amidst this favorable kinematic regime.

... Germany ... Benelux ...

Shallow polar-air convection is ongoing over Benelux and Germany. Low-level shear is rather strong, so that a brief/shallow mesocyclone, maybe producing a brief funnel/tornado cannot be ruled out. However, threat is too low for a categorical risk.