Storm Forecast
Valid: Mon 28 Jul 2008 06:00 to Tue 29 Jul 2008 06:00 UTC
Issued: Sun 27 Jul 2008 21:18
Forecaster: GROENEMEIJER

SYNOPSIS

Weak height gradients are present under a broad ridge that covers much of Europe. On its western flank an intense trough with an embedded low is initially 500 km NW of NW Spain and moves northeastward reaching SE England on Tuesday morning.

DISCUSSION

France, British Isles, Benelux, W Germany...

During the afternoon, 1000-2000 J/kg MLCAPE will likely form over northern France, extreme W Germany and the Benelux. There, dew points near 20 C are expected. Scattered thunderstorms will probably develop, that could produce some localized large hail and flash flooding problems. Shear is weak in this area.

Isolated storms are expected to develop over Great Britain and eastern parts of Ireland as well, where CAPE should be a bit lower.

Towards the evening, moisture is expected to spread further westward across W France and southern England on approach of the upper-level system. As deep-layer shear increases to 15-20 m/s and forcing for upward vertical motion overspreads the area, convective storm activity is expected to increase. A likely scenario is that convective storms form over western France during the afternoon and merge into a large MCS moving into England.

With 850 hPa winds near 15 m/s some strong and locally severe wind gusts are possible on the passage of this system. Overnight, as the system moves slowly, large amounts of precipitation will likely accumulate across southern and southwestern England, so that flooding problems are likely to occur there.

Balkans...

Across the indicated area of the Balkans rather widespread thunderstorms are expected to develop. Low to moderate CAPE and weak shear suggest that the threat of severe weather will be low. rather slow-moving storms could, however, cause some local flooding problems.