CONVECTIVE FORECAST - UPDATE
VALID 18Z SUN 26/12 - 06Z MON 27/12 2004
ISSUED: 26/12 18:07Z
FORECASTER: DAHL

General thunderstorms are forecast across the coastal regions of northern Spain.

General thunderstorms are forecast across the central Mediterranean regions.

SYNOPSIS

Intense large-scale upper trough will persist over SW Europe and the SW Mediterranean Sea through the remainder of this day 1 period ... with vort maxima at its E periphery maintaining large SFC low centered over the NW Mediterranean Sea.

DISCUSSION

...Mediterranean...
Model water-vapor fields indicate increasing moisture at upper levels withinh DCVA regime which is expected to cross the Tyrrhenian Sea and S Italy late this period. Also ... low-level theta-e advection over the SE Ionean Sea is expected which should both support scattered TSTMS. Though wind fields are fairly strong ... shear magnitude is limited ... and threat for severe TSTMS does not appear to be too significant. However ... an isolated mesocyclone or two may occur ... capable of producing large hail ... severe straight-line winds and possibly an isolated tornado.

Rather shallow convection should persist in the postfrontal environment ... shear should be quite weak and organized severe TSTM threat seems to be rather low. However ... strong wind gusts ... small hail and waterspouts could occur.

...N Spain...
N Spain may see some shallow TSTMS ahead of strong vort max rotating about the main trough ... however ... increasing diurnal low-level stabilization and lack of moisture influx into the central portions of Spain should limit TSTM threat. Expect decreasing TSTM activity in the northern portions during the next few hours as the vort max moves inland. Strong shear may support a few severe wind gusts during the next few hours in the coastal regions ... but allover severe TSTM threat should be rather low.

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