Storm Forecast
Valid: Sat 05 Dec 2009 06:00 to Sun 06 Dec 2009 06:00 UTC
Issued: Fri 04 Dec 2009 22:33
Forecaster: KOROSEC

A level 1 was issued for Aegean sea, southern Greece, western and southwestern Turkey mainly for excessive rainfalls and lesser extend for waterspouts and severe wind gusts.

A level 1 was issued for N Portugal and NW Spain mainly for excessive rainfalls.

SYNOPSIS

A negatively tilted trough over central Mediterranean and western Balkans transforms into the cut off low while moving SE-wards into the eastern Mediterranean. A deep trough over N Atlantic and western Europe reinforces again with a new rapidly developing cyclone west of UK. A new surface cold front moves into western Europe. Cool and stable conditions prevail over the rest of Europe.

DISCUSSION

... southern Greece, Aegean sea and WSW Turkey ...

The main storm activity is expected along the cold front associated with the surface low moving SE-wards. Ahead of the front, a few hundreds of MLCAPE will be avaialable beneath the rather weak upper level divergence. Large scale ascent will support numerous showers and thunderstorms to form, but mostly in the areas south of Greece which is outside of our forecast area. Upslope flow ahead of the trough favors an excessive rainfalls as the main threat mainly over the coastal Turkey, while a few severe wind gusts can occur within the more isolated storms more over extreme southern Greece. When CAA and steep LL lapse rates overspread the area, a few waterspouts will be possible as well.

... NW Iberian Peninsula ...

Quasi stationary frontal boundary will be extending from western France SW-wards towards NW Iberian peninsula where models simulate quite a lot of precipitation. While instability is very low, strong SW-erly flow and favorable LLJ in the warm sector suggests that persisting rainfalls will likely result. A large amount of precipitation and local flash floods can therefore occur especially over Galicia region.

... UK ...

As the deep trough over western Europe and northern Atlantic sea reinforces, another rapidly forming surface low takes place west of UK. Associated with the low, a cold front is pushed into western Europe. Within the moderately sheared environment, only weak signals of instability are present. Therefore a well organized convective line is not likely to form, but shallow linear convection can still occur. Given the quite high uncertainties present, no threat level was issued attm. Parts of western UK were included into low lightning probabilities as models suggest numerous showers and a few thunderstorms will form within the colder airmass behind the front.