Storm Forecast Valid: Sat 04 Oct 2014 06:00 to Sun 05 Oct 2014 06:00 UTC Issued: Fri 03 Oct 2014 19:35 Forecaster: GATZEN
A level 2 was issued for northern Tunisia and surroundings mainly for large hail and excessive precipitation and to a lesser extend tornaodes and severe wind gusts.
A level 1 was issued for the central Mediterranean mainly for excessive precipitation.
The European ridge amplifies and builds a blocking high across Scandinavia. Cold air advection from the east affects central Europe, where mid-level heights start to fall. Across western Europe, an intense lifting trough affects the UK and North Sea region. Its cold front will cross north-western France and the Benelux countries until Sunday morning. Weak lapse rates will only allow for shallow CAPE ahead of this cold front. Over southern Europe, centre of low pressure has shifted to the central Mediterranean. Northerly flow in the wake of the low will lead to dry air advection. Focus of convective development is therefore the base and eastern flank of the Mediterranean low and mid-level trough axis.
Southern and central Mediterranean
Rich moisture is present over the southern Mediterranean. Steep lapse rates are expected to advect offshore and will overlap with this moisture, creating high CAPE in the order of 2-3 kJ or more. CAPE will also evolve across northern Tunisia due to onshore moisture transport in response to the Atlas thermal low and sea breeze flow.
Thunderstorms are forecast to go on through-out the forecast period, initiating along land-sea breeze convergence lines, over the Atlas mountains, and along outflow boundaries. The most intense storms are forecast across and east of Tunisia where high CAPE overlaps with strong vertical wind shear exceeding 15 m/s in the lowest 3 km. Large hail and excessive rain are the main threat, but tornadoes and severe downbursts are not ruled out, especially when supercells can develop.
Further north, weak vertical wind shear will be present, but storm clusters will be capable of producing high precipitation and local flash flooding. This threat persists through the night, latest model guidance indicates the highest potential across the Ionian Sea and western Greece.