Storm Forecast
Valid: Wed 07 May 2008 06:00 to Thu 08 May 2008 06:00 UTC
Issued: Tue 06 May 2008 22:16
Forecaster: GATZEN

SYNOPSIS

Omega flow is centred over western Europe. Low-level air mass is well-mixed due to diurnal heating over most places. Rather steep mid-level lapse rates can be found especially over western Europe, where warm air mass spreads northward. Low-level moisture is poor over most of Europe. Weak CAPE is forecast to develop in the range of the axis of warm air over western Europe from Iberian Peninsula to France and British Isles as well as over northern Africa. Over the Balkans and east Mediterranean, some instability is also likely in the range of an upper low providing rather steep mid-level lapse rates.

DISCUSSION

Northern Africa

A strong upper jet streak moves eastward over south Mediterranean. The left entry of this jet will spread across northern Africa region during the period, and latest GFS model indicates low-level convergence from Algeria to northern Tunisia during the day. To the west, another jet streak reaches north-western Africa ahead of an Atlantic trough, providing QG forcing. Given easterly winds at low-levels, some moisture is able to spread into northern Africa, and CAPE will likely develop. Expect that isolated storms will develop over the mountains during the day, and isolated supercells are not ruled out given favourable veering profiles and around 15 m/s DLS. Isolated large hail as well as severe wind gusts may be possible. Storms are forecast to weaken after sunset over most places. From Morocco to northern Algeria, convective activity will likely go on in the range of a cold front moving eastward, and isolated large hail and severe wind gusts are not completely ruled out.

Iberian Peninsula

Ahead of the Atlantic trough, a moderate south-westerly flow is present over Iberian Peninsula. Embedded vort- max and upper jet streak will enter south-western Iberian Peninsula in the evening, spreading north-eastward providing QG forcing. Although low-level moisture is not quite well developed, CAPE is expected especially over the central nd northern regions of the Iberian Peninsula due to strong diurnal heating, and isolated thunderstorms are forecasts that will likely benefit from moderate DLS. Isolated mesocyclones may develop, capable of producing isolated large hail and maybe strong to severe wind gusts. Storms are expected to cluster ahead of approaching cold front that moves eastward during the night, while severe threat will gradually weaken due to decreasing instability.

France, British Isles

Quite steep lapse rates, moderate low-level moisture, and diurnal heating will likely assist for deep convection to develop during the day. Given weak vertical wind shear, chance for severe thunderstorms is weak. However, would not exclude isolated large hail with the stronger storms, though.
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