Storm Forecast
Valid: Fri 06 Oct 2006 06:00 to Sat 07 Oct 2006 06:00 UTC
Issued: Thu 05 Oct 2006 21:27
Forecaster: TUSCHY

SYNOPSIS

An intense upper-level trough will rapidly move towards the east, crossing Ireland and United Kingdom during the forecast period from the west....A broad pool of lower geopotential heights also covers most parts of the central Mediterranean, while a very warm airmass will be advected NE-ward on its downstream side over parts of SE Europe.
SW Europe will see dry and warm conditions under weak ridging.

DISCUSSION

...Ireland, United Kingdom, the English Channel, Scotland and the coastal areas of N-France...

At the beginning, a broad low-level pressure area will be located between Ireland and Iceland .... Strengthening CAA on its upstream side and an arriving 110kt upper-level jet max helped a trough to rapidly develop ( ~ 55N, 20W ), which will translate towards the east pretty fast.... This trough will be very well developed with a defined tropopause fold ( referring to the latest IPV analysis ) and adjacent jet configuration should support a rapid eastward motion of the trough axis.
During the morning hours, partially modified subtropical air will be advected over parts of S/SE UK, characterized by fine mid-level lapse rates and a quite high humidity content in the boundary layer.... Those positive points could be balanced by a pretty warm atmosphere, whith a stout cap in place.... Main focus for isolated TSTM development will be an area over extreme S / SE UK, the English Channel and the coastal areas of N-France, where a strong cold front should cross the regions from the west during the late morning / early afternoon hours.
Right now, the best chances should exist over N-France and extreme SE UK, where some diabatic heating and present airmass could support at least some marginal instability release.... Strong forcing should support the development of a few TSTMs along the eastward racing cold front.... Conditions would be favorable for severe wind gusts and a marginal tornado threat in an environment with low LCLs and enhanced LL shear.
Storms should rapidly move towards the east and activity will decrease from the west, when a dry slot works its way further towards the east.

The next area of concern will be Ireland and CNTRL UK / Scotland during the afternoon hours.....A pool of wrap-around moisture is forecast to reach Ireland during the morning hours, moving rapidly towrads the east.... GFS shows a well developed eastward moving moisture convergence zone and a broad area of low-end instability release over the level-1 area, due to cooling mid-levels....Intense 25m/s 850hPa jet should be present and each evolving storm would pose a significant severe wind gust threat, especially if storms line up.... Slightly veering profilers and low LCLs would be also conducive for a few tornadic storms to form.
During the early evening hours, the threat should ease from the W/SW , when warming at mid-levels and strengthening NVA will suppress new storm development.

...Belgium, the Netherlands, Denmark and parts of Germany...

Cold front will move onshore during the evening hours, affecting a broad area of NE France - Denmark.... Main inhibiting factor will be rapidly diminishing instability , but GFS indicates traces of negative LI-values far inland ( even spreading over NW/W Germany and SE France).
Expect a few isolated storms to develop over the coastal areas of the Low Countries, where onshore flow should help to bring some storms well inland....... and an area between NW Germany and Denmark, where a better thermodynamic environment ( and still pretty warm SSTs ) will be present.
Main threat will be a few severe wind gusts and a risk for an isolated tornado ( mainly along the coastal areas ).
Further inland, the weakening front ( Theta-E gradient becoming more diffuse ) and only traces of instability should confine TSTM development to the mountainous areas over SE-France / W-Germany.
An update may become necessary, if 12Z sounding datas indicate a better environment than currently anticipated.

....Central Baltic Sea...

Thermodynamic environment will become more favorable for TSTMs to form.... DLS of 15-20m/s and enhanced LL shear ( mainly along the coastal areas ) should be fine enough for a few storms to become severe with an enhanced severe wind gust / isolated tornado risk..... Expected storm coverage and severe weather threat does not justify a level-1 for the moment.

...Ionian Sea and an area S/SE of Sicily...

A stationary front will be the focus for storms to develop in an environment with moderate instability and about 20m/s DL / 10-15m/s LL shear, ( the latter one caused by a broad low-level area, which is forecast to develop S of Sicily , moving slowly towards the NE along the frontal boundary).... Storms should become severe with an attendant severe wind gust risk... Best shear ( especially at the lower levels ) and instability are forecast to be separated, but the area will be monitored, if storms also develop in the prefrontal airmass, where enhanced LL shear would be present .