CONVECTIVE FORECAST
VALID Fri 06 Jan 06:00 - Sat 07 Jan 06:00 2006 (UTC)
ISSUED: 05 Jan 21:11 (UTC)
FORECASTER: TUSCHY

Thunderstorms are forecast across parts of the central and eastern Mediterranean, western Iberia and across the English Channel

SYNOPSIS

Well developed high pressure area present over most parts of northern Europe... Cool and stable airmass will suppress any convective activity.
Main area of interest will be a southward dropping depression over SW Europe, reaching extreme NW Africa during the late afternoon hours.... Further eastward, broad area of lower geopotential heights will be present again, but a trend of slowly rising pressure is recognized in the model pool, which should cause a decrease in TSTM coverage...Small body of cold mid-level airmass, actually present over eastern France, will translate northward very slowly, reaching the English Channel during the afternoon hours...Expect a slight increase in cumuli development, when the core of this system will cross the Channel, but lack of moisture should preclude any significant TSTM development...however don't want to exclude an isolated TSTM in the marked area.

DISCUSSION

...SE Mediterranean...
Highlighted a broad area of TSTM possibility, but models show a continuos trend in TSTM decrease....Rising pressure and advection of drier air from Italy will only cause isolated TSTM development in the western TSTM area... Main threat for scattered TSTMs will be in the SEE TEXT area, where coldest mid-level airmass and highest moisture values in all levels will be present...A waterspout will be possible mainly along the coastal areas, but weak wind field should preclude any severe weather threat.

...Portugal and western/northwestern Spain...
Small area of enhanced cumuli development present [ center of developing depression ]west of France, which slowly shifts SEward...also first lightning strikes reported from this area...Models show arrival of the center during the early morning hours of the forecast period along the NW-coast of Spain....Expect isolated TSTM development along the path of the center [ coming onshore somewhere along the coastal areas of extreme NW Spain during the early morning hours ] , where LL shear will be slightly enhanced...there will be a risk for one or two tornadoes, but current thinking is that threat will be too marginal for issuing higher probabilities... Convective activity should become less important after landfall and should significantly decrease over Spain.
Pool of colder mid-level airmass will slide southward over Portugal and adjacent coastal areas... SST ~ 15°C, combined with this airmass should release up to 400 J/kg SBCAPE, only increasing further to the south (SST up to 17°C)...Low kinematic parameters present, so main threat will be a few waterspouts, mainly along the coastal areas of Portugal.

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