Storm Forecast
Valid: Thu 10 Mar 2011 06:00 to Fri 11 Mar 2011 06:00 UTC
Issued: Wed 09 Mar 2011 20:32
Forecaster: GATZEN

SYNOPSIS

Two cut-off lows affect southern Europe: One quasi-stationary to the west of Iberia and the other over Turkey that gradually weakens and moves eastward. Both cut-off lows are connected by a zone of relatively weak mid-level geopotential across the Mediterranean during the period. Farther north short-wave troughs travel eastward across northern Europe with a strong westerly flow. An embedded jet streak spreads from the British Isles and the North Sea into northern Germany and Poland. At low levels, cold and dry air masses are present over east Europe, whereas some low-level moisture spreads into Europe from the south-west.

DISCUSSION

Southern Iberia to Morocco

To the east of the cut-off low, thermodynamic profiles will slightly weaken during the next couple of hours. The temperature atop of the moist boundary-layer is forecast to increase, leading to more convective inhibition and decreasing low-level CAPE. Additionally, only weak forcing is expected as the mid-level jet weakens and low-level convergence will be weak. Current thinking is that the off-shore convection will go on during the period that will likely not organize given the weak vertical wind shear. Farther west, diurnal heating is expected to lead to instability release and some showers and thunderstorms are forecast. Although the wind profiles are not forecast to be favourable with only 10 m/s bulk shear in the lowest 3 km, the stronger cells may evolve mesocyclones capable of producing some large hail. The overall threat is forecast to be too weak for a level one, though.

Mediterranean Sea and Black Sea

Some weak instability is likely across the Mediterranean Sea and the Black Sea in the deeply-mixed cold air mass. Low-topped showers and thunderstorms are forecast. Organized thunderstorms are not expected given the weak forcing and vertical wind shear.

North Sea region

An intense surface low will move over the North Sea, leading to severe winds. The convective potential is expected to be weak as low-level moisture is rather poor. Some showers may be capable of producing isolated lightning, but organized convection that would enhance the severe weather threat is not forecast.