CONVECTIVE FORECAST
VALID 06Z SAT 08/01 - 06Z SUN 09/01 2005
ISSUED: 08/01 00:07Z
FORECASTER: VAN DER VELDE

There is a slight risk of severe thunderstorms forecast across Nrn Denmark, SWrn Sweden and extreme Srn Norway

General thunderstorms are forecast across Scotland, the North Sea, Srn and Wrn Norway, Srn Sweden

SYNOPSIS

Rapid cyclogenesis over Scotland deepens depression from 980 hPa to less than 955 hPa while moving towards Scandinavia. Pressure gradients and isallobaric effects will generate a field of tremendous low-level wind speeds in the order of >35 m/s at 850 hPa. At 06Z, the cold front will leave the UK and pass Denmark around 12Z. Showers and thunderstorms are expected to form in the unstable air behind the cold front.

DISCUSSION

...SEE TEXT area...
The strong wind field can cause damaging straightline wind gusts in excess of 30 m/s, especially at the cold front and by downward momentum transport due to convection. Convection is expected to be deeper and stronger especially within the TSTMS contour, however cold air advection may suppress convection by stabilising subsidence. Very strong 0-6 km and 0-1 km shear are forecast throughout the see text area, so some storms may develop bow echoes accompanied by severe gusts, or develop mesocyclones that may spawn an isolated but damaging tornado.

...SLGT area...
0-1 km shear >20 m/s, SREH >200m2/s2 and instability become maximized over this area by Saturday evening into the night. Models indicate some lift between subsidence zones. Some storms are expected to develop, accompanied by severe gusts, and an enhanced potential for a tornado given the strong kinematic fields.

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