Storm Forecast
Valid: Sun 04 Dec 2016 06:00 to Mon 05 Dec 2016 06:00 UTC
Issued: Sat 03 Dec 2016 22:51
Forecaster: KAHRAMAN

A level 1 was issued for the region around Starit of Gibraltar mainly for excessive precipitation, and chance of a tornado.

SYNOPSIS AND DISCUSSION

A ridge and weak mid-tropospheric flow remains over much of Europe. An intensifying high pressure covers a large area extending from British Isles to Turkey, separating relatively active weather systems in the N NE and S SW. The Norwegian Sea, Strait of Gibraltar with SW Iberian Peninsula, N Morocco and Alboran Sea, and parts of the Mediterranean are the regions where latent instabliity exists.

The cut-off low around Strait of Gibraltar is expected to weaken during the forecast period. MLCAPE will still be as high as 800-1000 J/kg offshore S Portugal in the morning hours, and extend over SW Iberian Peninsula with diurnal heating. Deep layer shear is less than 10 m/s in this part, increasing southwards due to the jet aloft, which also weakens until night. Little CIN, low level convergence and upper level divergence ensure initiation in this area. High PWs locally exceeding 30 mm, and slow storm motion vectors indicate an excessive precipitation risk. An isolated tornadic supercell is not ruled out around the Strait of Gibraltar/Alboran Sea, due to locally enhanced deep layer and low level shear.

Low to moderate instability, and weak kinematics exist over C and E Mediterranean Sea, where unorganized storms are forecast. Some large hail is possible around Ionian Sea, but no threat level is issued due to low confidence regarding the energy in the hail-growth zone. With easterly moisture advection, W parts will also have weak CAPE further in the night, resulting in pulse storms.

A deepening cyclone over Nordic countries will follow the previous low over E Europe, moving warmer air mass eastwards, while bringing Arctic air towards Norwegian Sea behind its cold front. A few hundred J/kg MLCAPE is forecast here during nighttime, with EL temperatures reaching -20 C. Storm organization should be rather limited.