VALID 11Z WED 13/11 - 06Z THU 14/11 2002
ISSUED: 13/11 11:42Z
FORECASTER: GROENEMEIJER

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHWESTERN IBERIAN PENINSULA, WESTERN FRANCE AND SOUTHEASTERN ENGLAND

GENERAL THUNDERSTORMS ARE FORECAST ACROSS THE IBERIAN PENINSULA, SOUTHERN AND WESTERN FRANCE, SOUTHERN BRITAIN, AND WESTERN IRELAND

SYNOPSIS

LARGE UPPER LEVEL TROUGH PRESENT WITH AXIS FROM JUST W OF THE BRITISH ISLES TOWARD THE IBERIAN PENINSULA. BAROCLINC WAVE PATTERN PRESENT ALONG EASTERN FLANK OF THE SYSTEM. AT THE BEGINNING OF THE PERIOD RAPID CYCLOGENESIS IS TAKING PLACE AT THE BASE OF THE TROUGH IN ASSOCIATING WITH A DEVELOPING WAVE.

DISCUSSION

...NORTHWESTERN IBERIAN PENINSULA...
RAPIDLY DEEPENING LOW-PRESSURE SYSTEM NEAR THE NORTHWESTERN TIP OF THE IBERIAN PENINSULA IS EXPECTED TO MOVE NORTHNORTHEAST. A STRONG WIND FIELD HAS FORMED ON THE EASTERN AND SOUTHERN FLANKS OF THIS SYSTEM. INSTABILITY OF THE AIR-MASS IN NOT PARTICULARLY IMPRESSIVE, BUT SATELLITE IMAGERY SHOWS WIDESPREAD CONVECTION HAS FORMED NEAR COLD-FRONT. LINEAR FORCING ALONG FRONT WILL LIKELY INDUCE FORMATION OF LINEAR CONVECTIVE MODES. SOUNDINGS IN AIR-MASS AHEAD OF FRONT SHOW THAT AIR AT MID-LEVELS IS QUITE DRY SO THAT EVAPORATIONAL COOLING MAY SIGNIFIVANTLY ENHANCE OUTFLOW WINDS. MAIN THREAT WITH THIS ACTIVITY WILL BE STRONG /UP TO 70KT/ WIND GUSTS. SOME SMALL HAIL MAY ALSO ACCOMPANY THE SYSTEM. CONVECTIVE ACTIVITY ON COLD FRONT WILL GRADUALLY WEAKEN DURING ITS EASTWARD MOTION OVER IBERIAN PENINSULA AS DRIER AIR FROM HIGHLANDS WILL REPLACE MOIST MARITIME INFLOW INTO SYSTEM.

...WESTERN FRANCE, SOUTHEASTERN ENGLAND...
OVER BAY OF BISCAY COLD FRONTAL CONVECTION WILL RETAIN ITS INTENSITY AFFECTING WESTERN FRANCE TONIGHT AFTER 20Z. MODELS DIFFER SIGNIFICANTLY ON STRENGTH OF BACKGROUND WIND FIELD, BUT STRONG GUSTS OF UP TO 70 KT WILL LIKELY BE POSSIBLE IN PLACES.

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