Storm Forecast
Valid: Thu 27 Jul 2006 06:00 to Fri 28 Jul 2006 06:00 UTC
Issued: Wed 26 Jul 2006 22:12
Forecaster: GATZEN

SYNOPSIS

Subtropic high over western Africa ridges into central Europe ... with a ridge axis from western Mediterranean to central Alps and further to central Scandinavia. Rather dry airmass is present east of the ridge axis ... and airmass is stable. To the west ... advection of EML takes place from southern France to central Germany. From eastern Atlantic ... short-wave trough enters Europe.

DISCUSSION

Northeastern Spain, France, western Alps, England, Benelux, western Germany

Rather strong upper jet streak is present at the eastern flank of propagating short-wave trough ... and QG forcing is expected as embedded speed maxima travel northwards over western Europe. At lower levels ... EML is present over most of the region. Latest soundings indicate that there is locally rich boundary-layer moisture ... especially near the Mediterranean Sea as well as along some frontal boundaries at the northern edge of the WAA regime from western/central France to Benelux region and eastern England. Latest soundings show CAPE in the order of 1500 J/kg locally. On Thursday ... WAA and QG forcing as well as daytime heating should lead to decreasing surface pressure ... and low-level convergence is expected from central France to eastern England ... where initiation should be most likely. Another focus for initiation should be northern Spain, where additional thermal low should lead to convergence ... as well as over western Alps. Thunderstorms that form will likely organize given enhanced vertical wind shear underneath the southerly jet streak. Given quite well-mixed boundary-layer ... cold-pool formation should likely occur ... and some clusters of storms should develop. Embedded mesocyclones are also expected given enhanced SRH values ... especially along the northern edge of French thermal low. Large or very large hail and severe wind gusts are forecast, while the chance for tornadoes is only enhanced locally. Persisting WAA and DCVA may lead to formation of a few MCS in the evening hours ... moving northeastward into Benelux/western Germany ... with severe wind gusts the main threat. However ... chance for tornadoes will be enhanced near the frontal boundary ... and a few events may occur over northern France, Benelux, and northwestern Germany. An upgrade to level 2 may be warranted when thermodynamic profiles will improve significantly and well-organized MCS will be likely.

Central Germany into central Scandinavia

WAA in the range of the ridge axis ... as well as some DCVA ... may lead to initiation in the well-mixed airmass. Focus should be old outflow boundaries ... where low-level moisture should be enhanced. Given weak vertical wind shear ... most significant severe threat should be severe downbursts and very isolated large hail ... but level 1 seems to be not warranted ATTM, though.