Storm Forecast
Valid: Tue 10 Apr 2007 06:00 to Wed 11 Apr 2007 06:00 UTC
Issued: Tue 10 Apr 2007 01:52
Forecaster: VAN DER VELDE

SYNOPSIS

Persisting high pressure from the southern British Isles to Italy... with low pressure systems affecting Scandinavia. An upper trough slides southeastward over Poland towards the Black Sea. The Iberian upper low has weakened and displaced itself to the Atlantic, but a trough extending over Spain. Numerous cells can pop up again, primarily over orographic features. An isolated landspout may be possible in the weakly sheared environment.

Warm air advection off Algeria near the midlatitude jet has caused cyclogenesis between Mallorca and Algeria. GFS indicates no surface based CAPE, but is weakly unstable for elevated parcels and may receive convective precipitation before afternoon. Strong shear and 0-3 km SREH are present due to the southwestern jet and low level flow from the northeast, but convection is not likely to be strong enough and not rooted near the surface, so that it would not profit from it.

GFS shows a weakening of 2-4 km lapse rates, for example over Italy and France, mainly due to subsidence as evidenced by several 12Z soundings of yesterday. Over Spain the same but likely due to convective mixing.

The trough over southeastern Europe may just cause some thunder over the southern Ukraine (a few 100 J/kg GFS MLCAPE) and Romania (tops -20C, lift over mountains and cyclonic vorticity advection).

Convection following the cold front over central Norway may produce severe gusts (perhaps >30 m/s)and an isolated tornado may not be ruled out, but instability is too weak for a convective threat level. Cold, dry (<2 g/kg) airmass will not support much thunder either.