Storm Forecast
Valid: Thu 29 Dec 2011 06:00 to Fri 30 Dec 2011 06:00 UTC
Issued: Thu 29 Dec 2011 05:24
Forecaster: GATZEN

A level 1 was issued for western and central Germany mainly for tornadoes.

SYNOPSIS

A trough expands into central Europe and merges with low geopotential over the central Mediterranean. In the wake of the trough, a broad ridge moves into western Europe. This will be associated with a strong mid-level jet streak/short-wave trough affecting the North Sea and Germany with lift.

DISCUSSION

North Sea, Germany, Benelux

Strong synoptic forcing is expected in the evening and night hours at the cyclonically sheared flank of the approaching jet streak. Lapse rates will steepen, while a tongue of low-level moisture is forecast to spread from the southern British Isles to Benelux and northern Germany. Especially over the North Sea region, warm sea surface temperatures will likely create some CAPE sufficient for thunderstorms. However, the strong lift may also allow for thunderstorms over central Germany during the night hours. The storms will likely be surface-based given the moist low-level air mass. Current thinking is that a line echo wave pattern can develop that will reach south-eastern Germany at the end of the forecast period.

Strong vertical wind shear especially at low levels is expected. 0-1km vertical wind shear will be around 15 m/s. This will likely result in a threat of isolated severe wind gusts as well as tornadoes.

Central Mediterranean

Broad low geopotential will allow for thunderstorms over the warm sea suface. Weak vertical wind shear is present and the potential of storm organization is limited. A few waterspouts are not ruled out with this convection.