Storm Forecast
Valid: Wed 06 Sep 2006 08:00 to Thu 07 Sep 2006 06:00 UTC
Issued: Wed 06 Sep 2006 07:48
Forecaster: GATZEN

SYNOPSIS

Omega flow pattern is present over Mediterranean ... with cut-off lows centered over southern Iberian Peninsula and north-eastern Libya ... and subtropical ridge from Tunisia to central Adriatic. Warm air mass is present over Mediterranean ... and latest soundings show stable low levels from Adriatic to Iberian Peninsula. Underneath the strong inversion ... boundary-layer moisture has started to recover locally ... especially over western Mediterranean. Over Greece/Turkey ... steep low-level lapse rates and dry boundary-layer was present. To the north ... ridge is present over western/central Europe ... while upper trough migrates eastward over north-eastern Atlantic ... reaching from Norway to England at the end of the period. Warm air mass spreads into western and central Europe east of the trough. Latest soundings show steep mid-level lapse rates originating from Iberian Peninsula over France and western Alpine region. At low levels ... boundary-layer moisture is rather well developed. Cool airmass is present from British Isles to Scandinavia and over eastern Europe. A strong upper jet curves around the upper ridge from Ireland to central Baltic Sea and further to western Balck Sea.

DISCUSSION

Eastern France, Alpine region, northern Italy

Rather steep mid-level lapse rates are present over a broad area. At lower levels ... moisture has increased yielding CAPE as indicated by latest soundings. During the day ... a weak upper trough migrates eastward over France. East of this trough ... weak nose/axis of warm air mass is expected to spread eastward from eastern France into Alpine region ... and convection that has already formed over France is also expected over Alpine region today. Best potential seems to exist over western Alps ... where rich low-level moisture was indicated by latest soundings. Limiting factor will be low clouds that should inhibit insolation at least during the morning. Over northern Alps ... mostly clear sky is present ... but low-level moisture is rather weak ATTM. However ... low-level moisture is forecast to increase during the day underneath the cap as indicated by latest GFS model run ... and this seems to be reasonable. South of the Alps ... insolation and low-level moisture will lead to CAPE today ... but limiting factor will be weak low-level forcing and initiation is questionable. Expect that showers and thunderstorms will form over western/central Alps during the day ... and additional thunderstorms may be possible over southern Germany and northern Italy in the afternoon/evening hours. Given some DLS in the range of upper jet east of propagating trough ... some thunderstorms may organize ... and multicells/mesocyclones are not ruled out capable of producing severe wind gusts and isolated large hail. Thunderstorms should rapidely weaken after sunset.

England

Shallow cold front moves southward over England today. Latest soundings show rich low-level moisture but strong inversion over England today. Given that stratiform clouds will break during the next hours ... CAPE should form ... but it is not expected that cap will break during the day south of the cold front. Along/north of the cold front ... showers and thunderstoms may form ... but QG forcing will be weak given weak DCVA and low-level CAA. However ... thunderstorms that develop will likely organize given strong DLS in the range of the upper jet over British Isles ... and a severe event is not completely ruled out.