Storm Forecast
Valid: Thu 07 Oct 2010 06:00 to Fri 08 Oct 2010 06:00 UTC
Issued: Wed 06 Oct 2010 18:53
Forecaster: GATZEN

SYNOPSIS

High geopotential extends over western and northern Europe. A closed low is centred over the western Black Sea region. Two short-wave troughs will affect Scandinavia and Iberia, respectively that are embedded in a south-westerly flow. Warm air advection is forecast over France and the British Isles. Cool and dry air masses over eastern Europe spread into the Balkans and Turkey.

DISCUSSION

Aegean to southern Turkey

Northerly surface winds advect dry low-level air into the Aegean and into Turkey. This will limit the potential for thunderstorms significantly. However, a strong mid-level jet streak that curves around the troughs periphery will enter the southern Aegean late in the period. Steepening lapse rates over the rather warm sea surface are forecast to result in weak instability, and showers or thunderstorms are forecast during the night hours. With very limited instability and rather weak vertical wind shear, severe thunderstorms are not likely.

Eastern Spain to Bay of Biscay

A short-wave trough moves northward over the Iberian Peninsula. At low levels, an easterly flow will provide moisture advection from the west Mediterranean Sea into the Iberian mountains during the day. Some lift provided by the mid-level trough is expected to be associated with steepening lapse rates and weak CAPE. Along a convergence zone, initiation of thunderstorms is expected in the afternoon hours. Thunderstorms that form will be mostly unorganized as the vertical wind shear is limited to 10 m/s even for the lowest 6 km. Later in the period, convective activity may spread into the Bay of Biscay where rather rich low-level moisture is present and does overlap with steep lapse rates originating from the Iberian Peninsula. Given the weak vertical wind shear, severe thunderstorms are not forecast.