Storm Forecast
Valid: Sun 28 Oct 2007 06:00 to Mon 29 Oct 2007 06:00 UTC
Issued: Sat 27 Oct 2007 19:19
Forecaster: GROENEMEIJER

SYNOPSIS

Sunday at 06:00 UTC... a cold front stretches from just off the Norwegian west coast across the northern North Sea and Britain onward over the southern Irish Sea. An upper-level shortwave trough initially near the Shetland Islands, moves quickly northeastward. It is followed by a slack ridge that precedes an intense trough that is expected to cross Britain during the second half of the evening and night.
An upper-level low centered over southeastern Germany moves southeastward reaching Bosnia on Tuesday morning.
Another upper-level low over northern Morocco moves slowly eastward to northwestern Algeria.

DISCUSSION

SE Spain, W Mediterranean, NE Morocco, Algeria...

In the northern and eastern sectors of the Moroccon low pressure area warm air advection is expected. In concert with weak DCVA this should sustain scattered and locally clustered convective storms within the indicated area. Weak vertical wind shear and weak instability suggest the threat of organized severe weather will be low with this system.

Adriatic Sea, W Balkans, W Greece...

Ahead of the approaching upper low, upward vertical motion will increase over the area as will thunderstorm coverage. Especially over the southern parts of the Adriatic Sea, an MCS may for early on Sunday in response to increasing low-level warm advection. The in part elevated nature of the system and moderate shear should limit the severe threat. High amounts of precipitation and small hail are possible however.

Britain...

On Sunday morning, an active cold front should move to the southeast over Wales and England. Given that 300-400 m2/s2 storm-relative helicity is predicted, the formation of one or two tornadoes within the convective line along the front cannot be ruled out. Shear, and forcing do however not appear to be exceptionally favourable, so that we refrain from issuing a threat level.
In the postfrontal environment, the passage of a major mid/upper-level trough during the evening an night will likely be accompanied by an increase in convective activity. Some of the storms will likely be thundery, but the overall coverage of lightning will not be large. Moderate wind shear and weak instability suggest a low severe weather threat.