Storm Forecast
Valid: Sat 24 Oct 2009 06:00 to Sun 25 Oct 2009 06:00 UTC
Issued: Fri 23 Oct 2009 21:57
Forecaster: KOROSEC
A level 1 was issued for Ionian sea, most of Greece and Aegean sea mainly for excessive rainfall, strong winds and lesser extent for tornadoes/waterspouts.
A level 1 was issued for parts of Ireland, Scotland and N England mainly for strong wind gusts and lesser extent for weak tornadoes.
SYNOPSIS
An upper level trough with strong surface low now acting as a cut off low located over central Mediterranean is slowly moving SSE-wards while it fills out during the forecast period. Accompanied by this low, a cold front continues to race eastwards from central Greece towards Aegean sea. Over western Europe, a rapid cyclogenesis will be moving across the UK during the day with a cold front across western Europe. Elswhere, high pressure areas over SW and N Europe with stable weather persist.
DISCUSSION
... Ionian sea, most of Greece and Aegean sea ...
Deep convection will continue developing along now slowly eastwards moving cold front. Models have quite high instability ahead of it, pushing MLCAPE locally well above 1000 or even above 1500 J/kg locally. The cold front will be extended from central Greece southwards across western Crete by morning hours and should not move further east than central Aegean sea by Sunday morning. Impressive instability and LL moisture (0- 1km mixing ratios 10-13 g/kg) and slow progress of the main frontal boundary will allow a couple of MCSes to form along it. There, an excessive rainfalls will become likely, especially over Crete and western Aegean Sea. Additionally, a threat for strong winds will be possible within the strongest cells or squall-lines. The southernmost cells, which will have better directional shear, could also bring an isolated tornado threat.
A level 1 was extended further west behind the main frontal activity as rather high LL instability, LCL heights near 1000m and slow moving storms could allow a couple of waterspouts to form over warm waters of southern Mediterranean.
... parts of Ireland, Scotland and N England ...
A strong surface depression will be forming during the day across UK while moving NE-wards. Accompanied by this system, a rapidly eastwards moving cold front will serve as a focus for some convective development in highly sheared environment. Vertical wind shear of near 30m/s in 0-6km and 10-15m/s in lowest 1km layer will be available in the warm sector ahead of the cold front. While a couple hundreds J/kg of SREH will be placed along/ahead of this boundary as well. Models somehow simulate the possibility for a weak instability along the front and a shallow convective line is possible along it. Then, the main threat will be strong winds while impressive LL shear/SREH poses a threat also for a couple of brief funnel clouds/tornadoes with the strongest cells.
... Galicia in NW Spain ...
Aforementioned cold front crossing western Europe will be quite stationary and only slowly moving southwards across NW-ern parts of Iberian Peninsula. Both GFS and ECMWF models agree that strong orographic rainfalls will take place onshore over Galicia and a couple tens of mm will be possible. As the deep convection is quite uncertain to take place and support additional excessive rainfalls, a threat level was not issued.
