Storm Forecast
Valid: Sat 10 Mar 2007 06:00 to Sun 11 Mar 2007 06:00 UTC
Issued: Fri 09 Mar 2007 23:49
Forecaster: TUSCHY

SYNOPSIS

Inclined omega weather pattern continues for the northern Atlantic and Europe.
An extensive pool of low geopotential heights can be found over the S-CNTRL and SE Mediterranean. A cold upper-level low will cross the W-CNTRL Mediterranean, moving towards the south, while another strongly inclined depression over the far eastern Mediterranean will shift towards the east.

An outstanding depression will evolve SE of Greenland peaking out with an estimated pressure of around 940hPa ! This system will maintain its strength during my forecast period under extremely favorable conditions.
Downstream of this intense system, rising geopotential heights over parts of western and central Europe will provide stable conditions.

The same for NE Europe, where cool and stable air will suppress any convective activity.

DISCUSSION

...Sicily - Crete...

Complex synoptic weather pattern continues for the next 24 hours over this area.
Again, global models like GFS indicate a broad area of at least low-end instability release. Trapani ( 12Z 09 March 07 ) indicated that only marginal cooling at mid-levels / some moistening in the PBL would have been needed for better instability release.
Numerous small UVV maxima are forecast to cross this area, but thermodynamic profilers won't change compared to yesterday.
Therefore the large TSTM area of yesterday will be divided into one area of enhanced TSTM possibility between Sicily and Crete and another region further towards the west, discussed below.
GFS indicates a constant mix - out of very dry air, penetrating towards the center of the depression .
Steep lapse rates, combined with nice PVA will provide enough instability release for scattered thunderstorms to develop. Shear will stay weak and no storm organisation can be expected.


...Balearic Islands - Sardinia...

Aforementioned upper-level low pressure will move towards the south, crossing the area during the daytime hours.
Attendant cool-down of the atmosphere will provide some low-end instability release and a few thunderstorms will develop.
Main uncertainty will be the effect of pretty dry air over the western Mediterranean.
Latest synop reports ( 22Z ) from S-France indicate strong offshore flow ongoing.
I went pretty far north with the TSTM area, because of nice dewpoints and a developing convergence line during the morning hours.
Shear will be too weak for any storm organisation.

A few storms outside of the highlighted areas can't be excluded, but coverage will be too low for including those regions into a general TSTM area.

...SW Norway / Sweden

A negatively tilted short-wave trough will rapidly cross the area from the west during a 12Z-18Z time-frame.
A combination of ~ -35°C at 500hPa and somewhat higher Theta-E values over SW Norway / Sweden will support some marginal instability release.
Forecast soundings from this region indicate that some low-end instability release will be possible.
Any convective system will be able to produce gusts at or above the severe weather limit.
Although speaking against climatology, parameters for an isolated tornadic supercell look reasonable, given the aggressive kinematic environment.
Main limiting factor will be the missing instability and therefore a level-1 will not be issued.