Storm Forecast
Valid: Sun 28 Dec 2008 06:00 to Mon 29 Dec 2008 06:00 UTC
Issued: Sat 27 Dec 2008 23:38
Forecaster: SCHLENCZEK

SYNOPSIS

An Omega-like blocking pattern with a huge upper high over W-central Europe will continue at least throughout the period. Over the northwestern and north-central Atlantic, a large upper trough stretches from the Arctic Sea to SW Iberia. Further south, a 50 m/s jet stream at 300 hPa stretches from the Azores to the Middle East. An upper cut-off low is centered over the Gulf of Genua and will move westward into southern France. Most convection is expected to develop in an environment with weak pressure gradients in the Mediterranean region.

DISCUSSION

...SW Iberia, N Morocco...

In the vicinity of a 40 m/s upper jet streak, relatively warm and moist air is advected into the southwestern part of Iberia. Remnants of the storms from last night may continue throughout the early morning. GFS simulates some hundred J/kg of CAPE there and about 10 - 15 m/s deep layer shear but an upper ridge builds . Expect a few relatively low-topped isolated storms with very sporadic lightning and a negligible threat of severe weather in that region.

...S Tyrrhenian Sea, SE Ionian Sea, SW Turkey...

Small areas with a few hundred J/kg of CAPE are located over the central / eastern Mediterranean and will be the focus for diurnally-driven convection. Although deep layer shear in order of 20 m/s is present, overall threat of severe weather should be rather low as forcing and instability are weak. An isolated large hail / severe gust event is not ruled out but a threat level is not issued. Lightning activity will be rather sporadic.