Storm Forecast
Valid: Wed 23 Aug 2006 06:00 to Thu 24 Aug 2006 06:00 UTC
Issued: Tue 22 Aug 2006 21:56
Forecaster: GATZEN

SYNOPSIS

Upper trough over Europe is weakening ... as surface pressure is rising over western Russia and northern Scandinavia. Center of European trough is expected over Belarus and moves eastward slowly. Another short-wave trough cuts off over The Channel region during the period. To the south ... strong upper westerly flow is forecast over Mediterranean ... with jet streaks in the range of the two cut-off lows, i.e. from southern British Isles/Bay of Biscay to western Alps and from Italy to central Balkans and further to Black Sea region. At lower levels ... hot and well-mixed airmass is remaining over Iberian Peninsula, northern Africa, and southern Turkey. To the north ... cooler airmass has been advected from the northwest.

DISCUSSION

Western Russia

Extremely eastern forecast region will be affected by deepening suface low pressure system. Warm sector should be east of the forecast region ... but latest model output shows that weak instability should also form in the range of the occlusion. Expect moist and slightly unstable airmass near the occlusion ... QG forcing in the range of strong upper jet streak and WAA regime should lead to embedded thunderstorms in mostly stratiform rain band. Due to rather stable boundary-layer ... severe threat seems to be limited. However ... some sunshine may be possible ... warming the boundary-layer and helping thunderstorms to become surface-based ... where they should benefit from strong LLS ... and given low LCL heights ... chance for tornadoes os expected to be enhanced ... and a couple of events ... including isolated strong tornadoes ... should be possible if this scenario comes true. Current thinking is that stratiform rain will be present ... and rather stable low levels should limit severe potential.

Southern British Isles, northwestern France

In the range of the second short-wave trough ... convectively mixed maritime airmass is expected over the region ... and showers and thunderstorms should likely form. Given strong vertical wind shear ... some organized tstms should be possible ... including shallow mesocyclones. Coverage of severe tstms is unclear ATTM ... given some CAA and rather weak QG forcing. However ... current thinking is that at least a few mesoclyclones will form ... and isolated large hail or tornadoes are not ruled out. Most significant threat should be severe wind gusts in the range of small bowing lines, though.