Storm Forecast
Valid: Thu 08 May 2008 06:00 to Fri 09 May 2008 06:00 UTC
Issued: Wed 07 May 2008 17:34
Forecaster: GATZEN

SYNOPSIS

Large scale weather situation does not change significantly during the period. While high pressure remains over west and central Europe, troughs are present over south-eastern and south-western Europe. At the southern edge of the former a strong mid-level jet propagates eastward across east Mediterranean, while rather weak winds are expected over most of western Europe ahead of the Atlantic trough. At lower levels, well-mixed and slightly unstable air mass has developed in the range of the high. Cool and dry air mass is present over eastern Europe.

DISCUSSION

Northern Africa

Another day with possibly severe thunderstorms is forecast across northern Africa on THU. Ahead of the upper trough axis reaching Morocco during the day, a tongue of warm and well mixed air mass spreads northward, while low-level easterly winds will go on north of a thermal low. As a consequence, some moisture will advect into northern Algeria und Tunisia, and CAPE will likely develop. Although rather large cap will be present most of the day, increasing forcing is expected in the range of a convergence zone ahead of a weak cold front entering Algeria from the west. Initiation is expected along this frontal boundary over the Atlas. Thunderstorms that form will likely become well-organized given favourable veering profiles especially to the east of the convergence line, and supercells may develop capable of producing large hail and severe wind gusts. Although low-level buoyancy will be limited, and cloud base will be rather high, a tornado is not ruled out at this time. Thunderstorms will likely merge into a MCS along the main frontal boundary, moving north-eastward while severe potential gradually decreases over the rather cold Mediterranean Sea as convection becomes elevated.

Central and northern parts of Iberian Peninsula

Ahead of the Atlantic trough, a weak convergence zone is expected over central Iberian Peninsula, leading to easterly winds over northern Iberian Peninsula. This will likely yield some moisture flux convergence over the central regions of the Iberian Peninsula. Given steep mid-level lapse rates, at least weak instability is forecast. Thunderstorms will likely form during the day, with single cells the main convective mode. However, moderate southerly winds at the 300 hPa level may help for some organization, and a few strong thunderstorms capable of producing large hail are not ruled out.

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