Storm Forecast
Valid: Sun 04 Feb 2007 06:00 to Mon 05 Feb 2007 06:00 UTC
Issued: Sat 03 Feb 2007 18:32
Forecaster: TUSCHY

SYNOPSIS

An awe-inspiring synoptic weather pattern is currently underway over the western Atlantic / E-Canada. Already whopping 225 kt ( 72403 ) were measured at 250 hPa on the SE side of an impressive Canadian polar vortex and models like GFS continue to indicate a powerful cyclogenisis somewhere over the Gulf of St. Lawrence in the left exit region of this 240kt-upper-level jet.
This constellation, marked by a highly diffluent streamline pattern west of Europe will bring no significant changes to the European weather ( e.g. no backing of the high pressure area over W-Europe ) .
Except for 3 places in Europe, weather conditions will be stable and unfavorable for thunderstorm development.

DISCUSSION

...Parts of Spain, Strait of Gibraltar and extreme SW Mediterranean...

Conditions will become marginal favorable for storms to develop over the area of interest. Weak pressure differences and no identifiable forcing will be present so main trigger should be the diabatic heating process. The low-levels will warm up a few degrees compared to yesterday and so does the 500hPa temperatures, which could offset the positive affect . Sounding modifications show not much space for instability release, but current thinking is that an isolated, weakly electrified thunderstorm will be possible as far inland as CNTRL Spain.
The same for the offshore areas, where mid-level warming will suppress any significant thunderstorm threat but won't exclude a short storm mainly during the morning hours.

...The Aegean Sea...

An SE-ward shifting upper-level trough will cross the area of interest during the daytime hours from the WNW and mid-/upper-levels will start a rapid cooling trend. A pool of very steep lapse rates will develop ( as -35°C at 500hPa will spread over the 13-15 SSTs of the Aegean Sea ) and widespread instability release sounds reasonable with possible readings of 300-500 J/kg SBCAPE.
Thunderstorms will evolve from about 9Z onwards and the threat will slowly shift towards the SSE.
The main activity will be separated from the strongest shear, but GFS indicates some convection in an area of 30m/s DLS where severe wind gusts and isolated large hail will be a distinct possibility.

...Coastal areas of Norway and Sweden...

A pool of extremely cold mid-level temperatures ( -40 to -45°C at 500hPa ) will affect the coastal areas of W-Norway during the daytime hours and will move onshore during the afternoon hours.
As a result lapse rates will steepen significantly and marginal instability release is denoted by global models even far inland.
The boundary layer will stay pretty moist and complex topography should support a few, short-lived thunderstorm events.
A path was highlighted, where positive UL-divergence, extreme low mid-level temperatures and a moist BL overlap .
Kinematic parameters will be favorable for an isolated tornado and severe wind gust event. Stronger cells could also contain isolated large hail due to a still enhanced background flow.
Thunderstorms will start to erupt over the Gulf of Bothnia during the latter part of the forecast period, but shear will be too low for an organized thunderstorm threat.