VALID 06Z THU 10/10 - 00Z FRI 11/10 2002
ISSUED: TUE 08/10 23:10Z
FORECASTER: HAVEN

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR WRN MEDITERRANEAN SEA...ITALY

GENERAL THUNDERSTORMS ARE FORECAST OVER AREA SURROUNDING THE SLGT RISK AREA

GENERAL THUNDERSTORMS ARE FORECAST OVER S FRANCE...WRN BALKAN STATES

SYNOPSIS

UPPER LOW OVER SPAIN IS MOVING SLOWLY EAST TO THE WRN MEDITERRANEAN SEA. STRONG JETSTREAM ON ITS SRN FLANK WILL ROTATE ALONG IT AND IS EXPECTED OVER TUNESIA, POINTING TWRDS CNTRL ITALY IN THE EVENING. AT THE SFC...COMPLEX SFC LOW OVER WRN MEDITERRANEAN IS MOVING EAST WITH COLDFRONT REACHING ITALY AT THE VERY END OF THE PERIOD.

DISCUSSION

...N-ITALY...
LATEST ECMWF MODEL CALCULATES STRONG LOW LEVEL PRESSURE GRADIENT N AND E OF THE SFC LOW THURSDAY AT DAYTIME: H85 WINDS WILL EXCEED 50 KT OVER PARTS OF NRN ITALY, NEAR THE LIGURIAN SEA. IN THIS HILLY TERRAIN SHEAR PROFILES CAN BECOME MODIFIED, CREATING FAVOURABLE CONDITIONS FOR SHORT-LIVED SUPERCELLS. GIVEN THE HIGH HODOGRAPH LENGHTS... DAMAGING WINDS WILL BE THE MAIN THREAT. A TORNADO WILL ALSO BE POSSIBLE, BUT HAIL SIZE WILL BE LIMITED DUE TO LOW CAPE.

...WRN MEDITERRANEAN SEA...CNTRL AND SRN ITALY...
AS 100+ KT H30 SPEEDMAX OVER N-ALGERIA, AT THE BEGINNING OF THE PERIOD, ENTERS THE MEDITERRANEAN IVOF ITALY, STRONG UVM WILL OCCUR, ESPECIALLY IN THE LEFT-FRONT QUADRANT OF THE JETSTREAK. AIRMASS WILL BE MOD UNSTABLE /CAPE ARND 1000 J/KG/ AND IN COMBINATION WITH 0-6 KM SHEAR IN EXCESS OF 50 KT...THIS WILL LIKELY RESULT IN STRONG TO SEVERE TSTMS WITH LOCALLY LARGE HAIL AND DAMAGING WINDS. JUST EAST OF THE COLDFRONT, WHERE SFC WINDS ARE HIGHER AND MORE BACKED... 0-3 KM SRH CAN BECOME SUFFICIENT FOR STORMS TO ROTATE, SO SUPERCELLS AND PERHAPS A TORNADO CANNOT BE RULED OUT. ELSEWHERE IVOF THE JETSTREAK... SHEAR WILL BE SUFFICIENT FOR SPLITTING TSTMS. AS IN MANY CASES WITH STRONG UVM, STORMS WILL LIKELY CLUSTER INTO LARGE COMPLEXES/MCS'S.

......
NEAR SW-TIP OF IBERIAN PENINSULA, ON THE SW-PERIPHERY OF THE UPPER LOW...VERY STRONG VERTICAL SHEAR IS EXPECTED. HOWEVER... CAPE WILL BE QUITE LOW, AND SUBSIDENCE DUE TO AN APPROACHING RIDGE WILL SUPRESS DEEP CONVECTIVE MIXING.

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