CONVECTIVE FORECAST
VALID 06Z SUN 25/01 - 06Z MON 26/01 2004
ISSUED: 24/01 20:38Z
FORECASTER: DAHL

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

General thunderstorms are forecast across the Biscay and W France.

SYNOPSIS

NWLY upper flow will stretch from the British Isles across SW Europe into the Mediterranean. Embedded vort max will move across Italy during the day ... and reach Greece towards the end of the FCST period. Another vort max will cross the Biscay and W France late on Sunday ... developing SFC low ahead of this feature is expected to be located over W France by Monday 06Z.

DISCUSSION

...Mediterranean...
It appears that a few lightning strikes will accompany the Italian vort max ... especially late in the day over the Ionian Sea. Degree of instability is uncertain ... but it appears that CAPE will be minimal and that any TSTM will likely be quite shallow ... yielding rather weak shear in the cloud-bearing layer. Severe TSTM threat should thus be minimal with this activity.

...Biscay/France...
GFS simulates weak CAPE in the warm sector of the cyclone over the Biscay by Monday 00Z. ATTM the warm-sector air mass is not sampled by radiosonde ascents ... and actual degree of instability is difficult to ascertain. However ... given relatively high theta-e values coherently simulated in the warm sector ... confidence that GFS' CAPE fields are not entirely unrealistic is sufficiently high to include the possibility of TSTMS along the cold front of the cyclone. TSTMS will likely be quite shallow ... and in the presence of quite meager CAPE ... rather strong deep-layer shear will likely not enhance severe threat drastically. Indications are that isolated elevated TSTMS will be possible late Sunday evening over SW France E of the warm front ... and over the Biscay/W French coast along the cold front late Sunday night/early Monday morning.

Large fields of Benard-type convection will likely persist across portions of the N Atlantic and the North Sea. Ahead of various small vort maxima ... convection is expected to be temporarily deep enough to produce a few lightning strikes. However ... TSTM coverage is expected to be too low for a TSTM area.

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