Storm Forecast
Valid: Wed 14 Nov 2007 06:00 to Thu 15 Nov 2007 06:00 UTC
Issued: Tue 13 Nov 2007 18:47
Forecaster: GATZEN

SYNOPSIS

Intense long-wave trough situated over Central Europe. It is filled with cold polar air mass that is also present over northern Europe. A strong jet streak is located at the western flank of this trough from north-eastern Atlantic to western France, and south-west Mediterranean that will spread into southern Adriatic and Balkans during the period. Strong QG forcing is expected at the cyclonic flank of the jet streak, and a surface low is forecast to deepen over central Adriatic. Another strong jet streak and associated intense surface low will affect northwestern Scandinavia at the end of the period.

DISCUSSION

South Mediterranean Sea

Latest soundings indicate that cold low-level air mass has flooded most of the Mediterranean. This air mass is characterized by quite steep low-level lapse rates and some shallow instability underneath a strong inversion at the 850/800 hPa level. At least over east Mediterranean, colder mid-tropospheric air mass leads to deeper instability.

During the period, another strong jet streak will enter the Mediterranean at the flank of amplifying European trough. Strong QG forcing is likely and latest models suggest that the inversion will become weaker over most places, especially over the central, and southern Adriatic. However, the development of CAPE will be limited to a few 100s J/kg given poor boundary-layer moisture. During the period, shallow convective activity is likely over the warm sea. It is expected that thunderstorms will be most likely underneath the cyclonic exit of the jet streak, spreading eastward during the period. Especially south of the low pressure center, strong vertical wind shear is forecast. While veering is not very favorable for mesocyclones, multicells seem to be the main convective mode. Severe wind gusts may occur with strong convective cells, as well as isolated hail, reaching severe limits. Furthermore, an isolated tornado is not ruled out near the cost, where low-level wind shear is forecast to be strongest. Additional thunderstorms are likely further south-east over the Aegean, where QF and low-level forcing will be significantly weaker. Although vertical wind shear will be rather strong near the coasts, is seems that only weak convection will develop ATTM.