CONVECTIVE FORECAST
VALID 06Z SAT 12/03 - 06Z SUN 13/03 2005
ISSUED: 11/03 20:59Z
FORECASTER: DAHL

General thunderstorms are forecast across the south-central Mediterranean Sea.

General thunderstorms are forecast across S Portugal and SW Spain.

SYNOPSIS

Large-scale upper low is covering NE Europe ... resulting in rather broad and intense W/NWLY upper flow over central portions of Europe. Small upper cut-off low will cross the central Mediterranean regions during the day ... with weakening Atlantic upper trough reaching the Iberian Peninsula late in the period. At low levels ... WAA should continue to spread northeastwards into Iberia and the SW Mediterranean Sea during the day ... otherwise ... deep polar air masses are dominating Europe.

DISCUSSION

...south-central Mediterranean...
Focus for convective activity will likely exist with the small ... initially intense Mediterranean vort max. Convection should be fairly shallow ... with essentially neutral environments. Deep- and low-level shear appear to be quite marginal ... and organized severe TSTMS are unlikely. However ... a waterspout or two could occur.

...S Portugal and SW Spain....
It looks that the subtropical air mass advecting into Portugal/Spain will become weakly unstable over extreme SW Iberia towards the afternoon as indicated by upstream soundings (ref. Friday's Funchal 12Z ascent) and latest model guidance. However ... lack of TSTM activity over the Atlantic in this air mass on Friday indicate bad handling of GFS and NMM with this setup ... both models having predicted positive CAPE and UVV's ... and confidence is thus somewhat limited that CAPE fields will develop as models indicate. Synoptic negative will be the weakening of the Atlantic upper system towards late afternoon. However ... S European March insolation may be sufficient to destabilize the air mass ... and a TSTM area seems to be marginally warranted.

...central Europe...
Scattered showers and an isolated TSTM or two may occur beneath thermal trough axis over north-central Europe ... but current thinking is that TSTMS will be too isolated for a TSTM outlook.

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