Storm Forecast
Valid: Mon 16 Jul 2007 06:00 to Tue 17 Jul 2007 06:00 UTC
Issued: Sun 15 Jul 2007 23:19
Forecaster: GROENEMEIJER

SYNOPSIS

A mid/upper low-pressure centre at the southern end of a longwave trough is located to the southwest of Ireland. Ahead of the through a strong southwesterly flow has advected an elevated mixed layer as far northward as southern Scandinavia.
Along the western edge of the warm air a strong SSWly jet is present.
Downstream, a ridge initially strechting from S Norway to the Czech Republic moves eastward and a trough from Karelia to the Moscow area develops into a weak cut-off low over the northern Russian Plains. This trough is filled with cold air that destabilizes in response to diurnal heating and is the location of scattered thunderstorms.

DISCUSSION

France, Belgium, Netherlands...

Two shortwave troughs are expected to affect the frontal zone over western France and the North Sea region. The first one is expected over the southern UK and Belgium Monday at 06Z. Ahead of the system an MCS is likely ongoing over the Benelux, the southern North Sea and possibly SE England. Strong wind gusts are possible with this system.
The system should move out onto the North Sea during the morning leaving a coast-parallel baroclinic zone in its wake, between cool moist air in the west, and hot, dry air in the east.

A second trough is expected to move into southwestern France around noon local time.
The approach of the system should cause upward motion steepening the lapse rates on top of the moist air thereby creating a poorly-capped 1000 J/kg MLCAPE over W-France, Belgium and later the Netherlands. Widespread renewed storm initiation is expected over western France during the afternoon and later over the western Benelux as well.

Given that deep-layer shear on the order of 30 m/s is expected, the storms will likely include supercells with a threat of large hail in addition to severe straight-line gusts.
As the low-level wind field strengthens over the Benelux during the evening hours a few tornadoes may form as well.

The strong low level winds will also aid to create an increasing threat of damaging winds, especially with storms organizing into a bowing MCS, which appears likely given the strong shear.