Storm Forecast
Valid: Wed 26 Jul 2006 10:00 to Thu 27 Jul 2006 06:00 UTC
Issued: Wed 26 Jul 2006 10:56
Forecaster: GROENEMEIJER

SYNOPSIS

At 9:00 UTC... a ridge is located roughly along an axis from Norway to southeastern France.
Upstream, an elongated trough stretches from just NW or Ireland to just W of Portugal.
A hot air-mass with steep low-level lapse rates covers most of Wrn Europe. Downstream, a cold front precedes a NE-SW-oriented trough over Finland and Karelia that moves further into northwestern Russia.

DISCUSSION

Wrn France...

A jet streak with 20 m/s wind speeds at 500 hPa is located just downstream of the trough from western Iberia into southern Britain. As the trough and jet shift slowly eastward, stronger shear overspreads western France. Small vorticity anomalies in the flow will liekly determine where baroclinic disturbances will form. It appears likely that frontogenesis will take place over western France. Given that capping on the warm side of the front is not very strong, this could well lead to the formation of scattered convection and likely one or two MCS's during the evening hours, that move Nwd to NNEwd. Because the boundary layer should be deep and relatviely dry, strong cold pools can form, leading to bowing elements accompanied by damaging surface winds. In addition, isolated large hail will be possible. The severe threat should gradually diminish overnight.

England, Scotland, Wales...

The development of scattered convective storms is expected over much of Britain. Given rather strong deep-layer shear on the order of around 15 m/s, well-organized multicells are likely. Clustering of multicells into southward back-building systems is possible, locally providing an enhanced threat of flash flooding. Additionally, strong to severe wind gusts and some large hail are likely to occur. The severe threat should diminish after sunset.

Benelux, Wrn Germany, Wrn Alps, Ern France...

Although weak forcing and wind shear are in place across these areas, some threat of severe weather will exist in those areas as isolated storms develop during the afternoon hours. Deep, dry boundary layers will create a favourable environment for strong convective gusts and large hail. The severe threat should diminish rather quickly after sunset.