VALID 06Z SUN 24/11 - 06Z MON 25/11 2002
ISSUED: 23/11 16:07Z
FORECASTER: HAVEN

THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS SWRN MEDITERRANEAN SEA

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS EXTR SRN IBERIAN PENINSULA, WRN MEDITERRANEAN SEA INTO NRN ITALY

GENERAL THUNDERSTORMS ARE FORECAST ACROSS U.K. COASTAL AND SURROUNDING SEA AREAS

SYNOPSIS

UPPER LOW WEST OF BRITISH ISLES IS STATIONARY. AMPLYFING UPPER TROUGH WEST OF BISCAY AND WEST OF PORTUGAL IS SLOWLY SHIFTING EAST. STRONG 100+ KTS JETSTREAM IS CURVED AROUND THIS TROUGH. SEVERAL VORT MAXIMA ARE ROTATING TROUGH THIS UPPER FEATURE OVER SWRN PARTS OF EUROPE. MAIN BAROCLINIC ZONE IS SITUATED FROM WRN ALPES TO W-SPAIN TO MAROCCO.

DISCUSSION

...WRN MEDITERRANEAN SEA...
STRONG DCVA WILL OCCUR OVER WRN MEDITERRANEAN AS SHORTWAVE ROTATES THROUH BASE OF LARGE SCALE UPPER TROUGH. THIS AND WAA FURTHER NORTH, WILL RESULT IN A DEEPENING SFC LOW OVER SPAIN AND SRN FRANCE LATER. MODELS CALCULATE CAPE ON THE ORDER OF 500 J/KG. TOGETHER WITH 0-6 KM SHEAR OF 45-55 KTS, THIS WILL BE SUFFICIENT FOR ORGANIZED THUNDERSTORMS, PROBABLY ARRANGED INTO LINES. STORMS MAY BE ACCOMPANIED BY SEVERE WINDGUSTS OF 50-65 KTS AND (MARGINAL) LARGE HAIL.

...SWRN MEDITERRANEAN SEA...
NEXT SHORTWAVE IS MOVING OVER MAROCCO AT NIGHT AND REACHING SWRN MEDITERRANEAN MONDAY MORNING. WAA AND DCVA WILL BOTH CONTRIBUTE TO FURTHER CYCLOGENESIS OVER WRN MEDITERRANEAN, SW OF BALLEARICS LATER IN THE PERIOD. BACKING AND INCREASING SFC WINDS AHEAD OF THE SFC LOW TO AND EASTERLY 25+ KT DIRECTION BELOW SW 50 KT WINDS AT 500 HPA WILL CREATE A VERY FAVOURABLE ENVIRONMENT FOR SUPERCELLS. DAMAGING WINDS, LARGE HAIL AND PERHAPS A TORNADO ARE ALL POSSIBLE WITH ANY STORM THAT FORMS. SINCE SOME MODELS CALCULATES HIGH WINDSPEEDS ARND THE SFC LOW TOGETHER WITH THE RISK OF SEVERE CONVECTIVE WEATHER...THIS AREA AND PERHAPS S-PORTUGAL/SPAIN NEEDS TO BE CLOSELY MONITORED.

...U.K. COASTAL AND SURROUNDING SEA AREAS...
ISOLATED SHOWERS/THUNDERSTORMS WILL DEVELOP IN POLAR AIRMASS OVER SEA AND COASTAL AREAS, ESPECIALLY WHERE SFC CONVERGENCE IS ENHANCED AND IN WEAKLY DEFINED DCVA-AREAS. LOW INSTABILITY AND WEAK VERTICAL WINDSHEAR WILL MINIMIZE SEVERE THREAT.

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