Storm Forecast
Valid: Mon 03 Dec 2018 06:00 to Tue 04 Dec 2018 06:00 UTC
Issued: Mon 03 Dec 2018 02:13
Forecaster: VAN DER VELDE

A level 1 was issued across France, Switzerland and southern Germany for tornadoes and severe wind gusts.

A level 1 was issued across the eastern Mediterranean, southern Turkey and Cyprus mainly for excessive convective rainfall, large hail and tornadoes.

SYNOPSIS

Between a Morocco/Iberia high and northern European low at 500 hPa, a strong westerly flow is present over the central latitudes of Europe, with 40-50 kts at 700 hPa to 80-100 kts at 300 hPa. These conditions overlap with a moderately warm sector over Western Europe with Atlantic dewpoints advected into central France of 11-12 degrees. Enhanced mid-level lapse rates are left over western/central Europe in the wake of frontal systems now passing over the Baltics. A trough at 06Z WSW of Ireland with a clear PV feature moves ESE-ward into France and then sinks toward Italy in the second half of the night. Various models predict development of a few hundred J/kg CAPE over France and surroundings, and the passage of the trough coincides with modest diurnal heating, and deep convection is likely to develop.


DISCUSSION

...France, Switzerland and southern Germany...

A zone of unstable air will become activated by the passage of a trough, with clustered convection occurring in a high wind shear environment. The 0-1 km shear vector values of about 12 m/s supports tornadogenesis, while mescyclones can be sustained by SREH of a marginal 150 m2/s2 and 0-6 km shear of 20 m/s. Mean wind speed in low to mid levels supports gusts of around 25 m/s in convective downdrafts.
As there is no particular linear surface convergence or frontal feature associated with the passage of the trough, a well-organized linear convective system is not likely, save for local bow echo patterns, and the dominant severe weather will be isolated tornadoes and isolated to sccattered severe wind gusts.


...southern Turkey, Cyprus...

A low pressure system centered west of Cyprus is accompanied by moderate instability and convergence zones focused on the Turkey and Cyprus coasts. Excessive rainfall can result, with flash floods. Isolated large hail may occur as SREH reaches favorable values for mesocyclone formation around Cyprus. Waterspout type tornadoes are also likely to occur.