Storm Forecast
Valid: Sat 17 Nov 2012 06:00 to Sun 18 Nov 2012 06:00 UTC
Issued: Fri 16 Nov 2012 20:25
Forecaster: TUSCHY

SYNOPSIS

Yesterday's sharp upper trough over W-Europe becomes flat and ill defined while entering the W-Mediterranean area. Together with another trough over SE Europe, both features assist in 500 hPa temperatures of aob -18°C for nearly all of Europe despite Italy. Hence, unsettled weather continues over most of the Mediterranean with quiescent weather further north (convective-wise).

At the surface, yesterday's 1000 hPa depression west of Portugal moves slowly to the SE with a constant weakening trend forecast. Otherwise no serious low pressure area is forecast to affect parts of Europe.

DISCUSSION

... Portugal, parts of Spain and the E/W-Mediterranean ...

With a cold upper trough atop and influx of subtropical air at lower levels, moderate SBCAPE build-up of 500-800 J/kg is anticipated with peak values along the coasts and over far S-Portugal. DLS will be very weak, so ill defined thunderstorms are forecast, probably clustering betimes. On the mesoscale, locally enhanced LL shear and better LL CAPE along any mesoscale boundary may provide another opportunity of an isolated tornado event, before thermodynamic set-up becomes worse after 15Z. Hence, next to an isolated waterspout/tornado event, the main risk will be heavy rain due to slow moving thunderstorm clusters. The activity gradually weakens from north to south and exits our forecast area after 00Z.

Further east, over the W-Mediterranean, weak shear but SBCAPE of 500-800 J/kg provides an adequate environment for isolated to scattered thunderstorms, which grow upscale into numerous smaller clusters. Heavy rain will be the main hazard due to a slow storm motion, but an isolated waterspout event can't be excluded with expected thermodynamic profiles at low-levels.

The exact same risk exists for Crete and surrounding areas although a decline in thunderstorm intensity and coverage is forecast from west to east during the overnight hours.

No area provides enough focus for a concentrated severe thunderstorm risk, so no level area was added.