Storm Forecast
Valid: Thu 08 Dec 2016 06:00 to Fri 09 Dec 2016 06:00 UTC
Issued: Wed 07 Dec 2016 19:51
Forecaster: GATZEN

SYNOPSIS / DISCUSSION

Large-scale flow over Europe curves around a ridge centred across the south-west of the continent. Embedded in the polar jet, a short-wave trough moves from the British Isles across the North Sea into Germany on Thursday and is expected over the northern Balkans on Friday morning. Downstream, a short-wave trough leaves the forecast area over southern Turkey. Northern Africa is affected by a cut-off low.

Pretty meagre low-level moisture is present over most portions of Europe. Moist maritime air masses spread from the British Isles into southern Scandinavia and later also into northern Germany, Poland, the Baltic States, and Belarus. Rich moisture is also present over the southern and south-western Mediterranean Sea.

Given weak lapse rates over the continent, the southern Mediterranean Sea is the only region with significant CAPE (about 500 J/kg). Weak vertical wind shear and also limited forcing is expected, so unorganized clusters of mostly off-shore storms are forecast. Locally, excessive precipitation is not ruled out over north-eastern Tunisia, given the long fetch of easterly moist flow. However, absence of forcing processes (e.g. frontal convergence) limits this potential, so a level 1 was not issued.

Sicily will likely be affected by heavy precipitation from the east as well. However, latest models indicate weak lapse rates and embedded convection will only slightly increase the threat. Consequently, this is not included in a level 1 as well, although local flooding is well possible, e.g. along the slopes of the Etna volcano.