Storm Forecast Valid: Sun 17 Aug 2014 06:00 to Mon 18 Aug 2014 06:00 UTC Issued: Sun 17 Aug 2014 05:38 Forecaster: VAN DER VELDE
A level 2 was issued for eastern Greece, eastern Bulgaria and Black Sea mainly for excessive convective rainfall and isolated large hail.
A level 1 was issued for parts of North Sea, Denmark, Norway, Netherlands, Germany and Finland mainly for isolated excessive precipitation and tornadoes.
A large low pressure of under 990 hPa deep enters the North Sea. Unseasonably strong pressure gradients surround the low over the British Isles, Benelux, Germany, Denmark, Poland and Baltic Sea. The advection of cold upper air over relatively warm sea surfaces results in MLCAPE values of several hundred J/kg. The unstable air resides behind a mid-level cold front which slowly will move over northern Netherlands, Germany and Denmark. Over Russia the remnants of an upper trough still trigger widespread convection. A much more active trough passes over Greece into the Black Sea with strong QG lifting. The very moist low-level flow over the Black Sea is northeasterly, directly opposite to the winds at 500 hPa, resulting in strong vertical wind shear. Over the Iberian Peninsula the Saharan Air Layer (dry, steep lapse rate mid level airmass) returns in response to advection from the south in advance of a large amplitude mid level trough coming from the Atlantic. The predicted GFS CAPE appears to remain mostly capped until Monday afternoon, but isolated showers from elevated parcels could occur.