Storm Forecast
Valid: Mon 08 Dec 2008 06:00 to Tue 09 Dec 2008 06:00 UTC
Issued: Mon 08 Dec 2008 05:31
Forecaster: VAN DER VELDE

SYNOPSIS

Central Europe is under the influence of weak high pressure following the eastward displacement of a large upper trough into Ukraine, the eastern Balkan and Turkey. An upper cut-off low over Spain reaches the Mediterranean coast on Monday evening, where the combination of somewhat cold air aloft and supply of relatively warm humid air will generate thunderstorms and abundant precipitation.

DISCUSSION

...Spain...

While GFS indicated some SBCAPE (but no MLCAPE) and cold EL temperatures, the upper low has hardly produced electrified convection during the previous days. Satellite does reveal convective structures. The profiles are nearly neutral and saturated, which prevents strong enough updrafts, and further destabilization is unlikely as mid levels have higher theta-e than lower levels, and the latter decreases, per GFS.
However, strong convergence and upward motion is predicted over the east coast of Spain, especially between Valencia and Costa Brava, where some storms can form. 0-500m lapse rates are not so steep as they were during recent entries of upper lows and in the mid levels the profiles will likely remain close to neutral. Winds perpendicular to the coastline can create lift and hence long-lasting precipitation.
Vertical shear is nearly absent.