Storm Forecast
Valid: Fri 09 Feb 2007 06:00 to Sat 10 Feb 2007 06:00 UTC
Issued: Thu 08 Feb 2007 21:27
Forecaster: TUSCHY

SYNOPSIS

A highly disturbed weather pattern will set-up / continue for most parts of Europe during the next 24 hours.
First swath of very cold air from the re-intensifying Canadian polar vortex was responsible for creating a zonally elongated and intense baroclininc region over the N-CNTRL Atlantic. Adjacent strong jets will support numerous intense cyclogenesis.
One of those cyclones,transitionally reaching a pressure of about 955 hPa WSW of Ireland, will reach the extreme western parts of Europe as a negatively tilted upper-level trough.
A developing LL depression over the western Mediterranean will rapidly move towards the south-east, reaching Sicily during the end of my forecast period.
Finally, a strong cold-core system will affect parts of N-Norway.
Eastern Europe will see cold and stable conditions under a slowly departing high pressure area.

DISCUSSION

...W / CNTRL Mediterranean...

An upper-level trough will cross the area from the west and will continue to grow as a consequence of an arriving intense 300hPa jet streak. This will place most parts of the W-CNTRL Mediterranean under the favorable left - exit region with strong UL divergence signals present in latest model output.
The global models are pretty consistent in developing a strengthening LL depression somewhere around Sardinia ( central pressure possibly under 1000hPa ), which will cross the area of interest from WNW towards the ESE.
SSTs increase to about 15-16°C and those temperatures in combination with a -25°C cold pool at 500hPa will be supportive for up to 500 J/kg SBCAPE relase south of Sardinia and south of Sicily.
Main focus for severe thunderstorm development will be an eastward racing and well developed cold front reaching NW Algeria at about 12Z and N-Tunisia only 4-5h later.
The main limiting factor for a more robust thunderstorm threat well inland will be the rapidly decreasing instability over N-Algeria.
Strongest forcing and UL divergence will also be displaced towards the north, although forcing along this cold front will still be fine. Despite those negative facts expect a few topographically supported storms to develop well inland.
Otherwise, kinematic parameters along the coastal areas will be favorable for an enhanced severe wind gust and tornado threat. Constantly steepening mid-level lapse rates will also favor an isolated large hail risk.

Main reason for sticking with a level-1 is the fact that strongest DLS and best instability fields will stay well separated during the whole forecast period.

...Bay of Biscay and coastal areas of W-France...

The cold front of aforementioned intense and highly negatively tilted upper-level trough will cross the Bay of Biscay 00Z onwards and will reach the coastal areas during the end of my forecast period.
Main concern arises in the postfrontal airmass, where marginal instability release and intense LL shear overlap far inland over W-France. Models like GFS indicate a strong convective signal and there are no indications that instability release will not take place.
Ingredients for tornadic thunderstorms will exist although GFS indicates a slight increase in LCLs.
Main uncertainty will be the timing of the cold front, which could finally have an impact on expected extent of severe weather during my forecast period. If models converge with a faster solution, an update may become necessary later - on.