Storm Forecast
Valid: Tue 02 Jan 2007 06:00 to Wed 03 Jan 2007 06:00 UTC
Issued: Mon 01 Jan 2007 19:46
Forecaster: TUSCHY

SYNOPSIS

Strong ridging over far SW Europe and a broad, cyclonic vortex over Norway, Sweden and parts of Finland support an influx of somewhat cooler air over N / CNTRL Europe.
A lee-cyclogenesis south of the Alpes experiences favorable conditions for signficant strengthening, while shifting towards the SE / ESE later in the day.

DISCUSSION

...Coastal areas of western Norway...

An outbreak of very cold air from E-Greenland will support a broad area of at least low-end instability release NE of Scotland - W of central Norway.
The main concern right now is the airmass quality, characterized by very dry low levels. Some PBL modification will occur, but in combination with weak forcing, no significant thunderstorm threat will be expected.
SSTs of at or above 7°C just west of central Norway and better LL airmass quality will support isolated to scattered storms to develop. Best waterspout conditions will occur in the highlighted areas, where very steep LL lapse rates and general weak DLS overlap.

...Parts of Scotland and United Kingdom...

Best chances for a few storms to develop will occur on the cyclonic side of an intense upper-level jet, pointing from the NW towards the SE over UK.
Moderately enhanced UVV values due to an SE-ward shifting upper-level wave will be enough for isolated thunderstorms to evolve in an uncapped environment.
Time - frame for storms will be limited between 06Z - 12Z and this should restrict storms to the morning hours, where LL lapse rates are still pretty weak.
Kinematic parameters and low LCLs would favor an isolated tornado / severe wind gust risk all the way down form Scotland to SE-UK maximized along the coastal areas and over SE UK.
Expected threat and storm coverage will be too low for warranting a level-1.

... Parts of France, Belgium, the Netherlands, Germany, Denmark, the southern Baltic Sea and adjacent areas and Switzerland...

A splitting pool of very cold mid-level air will cross the aforementioned areas from the NW / WNW. A broad area of low-end instability release can be expected.

First area of interest will be France, Belgium, the Netherlands and Switzerland mainly during the 12Z - 20Z time - frame.
A SE-ward shifting upper-level wave and accompanying mid-level cold pool ( 500hPa < -35°C ) will support enough lift / instability release for isolated - scattered storms to develop. Low LCLs and a wide area of 150-250 J/kg SRH1 will be conducive for funnels / short-lived tornadoes mainly along the coastal areas due to a better moisture content.
Topography could become supportive for an isolated thunderstorm threat over Switzerland during the later evening hours,too .
Dependant on how far west storms will develop, enhanced DLS and steep mid-level lapse rates could support an isolated large hail risk.

The other area of interest will be the extreme SE North Sea and S-Baltic Sea.
Kinematic / thermodynamic parameters will be the same like further towards the west . Conditions for waterspouts become increasingly favorable, although LCLs won't be that low during the daytime hours.
The threat will shift eastward betimes.

... Central and parts of the eastern Mediterranean...

Intense LL depression will rapidly shift towards the SE - ESE, while intensifying.
LL wind field will be supportive for severe thunderstorms over a pretty large area, but separation of best instability and shear should limit the risk for widespread organized storms.

Rapidly steepening lapse rates over the Adriatic Sea will support an enhanced waterspout risk and hence a level-1 was issued.
The main cocern for organized thunderstoms arises over the Ionian and Aegean Sea ( 15Z onwards ). Instability fields look marginal, but impressive upper-level divergence / UVV values indicate the possibility for a forced line of storms to develop along an eastward moving cold front will exist and an update/ upgrade may become necessary due to a significantly enhanced severe-damaging wind gust risk.