VALID 00Z THU 10/10 - 00Z FRI 11/10 2002
ISSUED: WED 09/10 23:58Z
FORECASTER: GROENEMEIJER

THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FOR SOUTHWESTERN ITALY AND SURROUNDING WATERS

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR AN AREA SURRIOUNDING THE MODERATE RISK AREA INCLUDING CENTRAL ITALY, THE MEDITERRANEAN SOUTH OF THE BALEARES, THE ADRIATIC AND THE ADRIATIC COAST OF THE BALKANS

GENERAL THUNDERSTORMS ARE FORECAST OVER AREA SURROUNDING THE SLIGHT RISK AREA INCLUDING SOUTHERN SPAIN, SOUTHEASTERN FRANCE, THE ALPS AND THE WESTERN BALKANS

SYNOPSIS

VERY COMPLEX PATTERN IS NEAR UPPER LOW OVER WESTERN MEDITERRENEAN. A STRONG JET IS PRESENT SOUTH OF UPPER LOW OVER WESTERN MEDITERRENEAN AND IS SPREADING NORTHWARD. THIS JET FURTHER INTENSIFIES IN RESPONSE TO INCREASING THERMAL GRADIENT WHILE VARIOUS VORTICITY MAXIMA ARE BEING ADVECTED.

DISCUSSION

...ITALY, ITALIAN ISLANDS, CORSICA, WESTERN BALKANS AND SURROUNDING WATERS...
AXIS OF HIGH VORTICITY IS DEVELOPING FROM BALEARES TO CENTRAL ALGERIA AND EXPECTED TO BE ADVECTED NORTHEASTWARD WITH RISING MOTIONS AHEAD OF IT. CONVECTION NOW OVER ALGERIA IS ASSOCIATED WITH THIS SYSTEM. SYSTEM WILL DEVELOP INTO A COLD FRONT BY EARLY MORNING AS IT ENCOUNTERS THE STRONG WARM ADVECTION OVER CENTRAL MEDITERRENEAN. CONVECTION WILL INTENSIFY AS BOUNDARY-LAYER MOISTURE INCREASES. CONVECTIVE SYSTEM IS EXPECTED TO AFFECT SICILY IN THE MORNING, THE MAINLAND OF ITALY IN THE AFTERNOON AND POSSIBLY THE WESTERN BALKANS IN THE LATE EVENING. AS MID-LEVEL WINDS ARE ON THE ORDER OF 40-50 KT AND DECENT DIRECTIONAL SHEAR AT LOW-LEVEL IS EXPECTED, A PART OF THE STORMS WILL LIKELY BE SUPERCELLS. CONVECTION WILL INCREASINGLY ORGANIZE INTO ONE OR MORE LINEAR MCS'S, ESPECIALLY AS SYSTEM MOVES OVER ITALIAN MAINLAND WHERE LOW LEVEL SHEAR IS EXPECTED TO BE SOMEWHAT LESS BEFORE IT INCREASES AGAIN NEAR THE BALKAN COAST. BOTH DAMAGING WINDS AND /VERY/ LARGE HAIL WILL LIKELY BE ASSOCIATED WITH THE SYSTEM. THERE IS SOME CHANCE OF TORNADO'S/TORNADIC WATERSPOUTS, ESPECIALLY IN THE MDT RISK AREA, WHERE CONVECTION IS EXPECTED TO BE THE MOST ISOLATED, LOW-LEVEL SHEAR IS THE STRONGEST, AND INSTABILITY MAXIMIZED. THE COLD FRONT WILL LIKELY SLOW DOWN DURING THE EVENING AND ONE OR TWO FRONTAL WAVES MAY GRADUALLY FORM ON WHICH CONVECTION WILL BE FOCUSED. IN THE AFTERNOON AND EVENING SURFACE CYCLOGENESIS IS LIKELY TO TAKE PLACE IN THE GULF OF GENUA IN THE LEFT EXIT REGION OF AN APPROACHING JET-STREAK. THE SURFACE LOW HAS THE POTENTIAL TO PRODUCE A STRONG WIND-FIELD OVER THE NORTHERN THYRRENEAN SEA AND VERY HIGH PRECIPITATION RATES OVER CORSICA AND NORTHERN ITALY IN THE EVENING HOURS.

...MEDITERRANEAN SEA SOUTH OF BALEARES...
SURFACE CYCLOGENESIS IS EXPECTED TO TAKE PLACE NEAR BALEARES. 40 - 45 KT 850 HPA WIND FIELD IS EXPECTED TO DEVELOP ALONG SOUTHERN FLANK OF THIS SYSTEM. MARGINAL TO MODERATE INSTABILITY IN COMBINATION WITH EXPECTED SHEAR PROFILES WILL ALLOW FOR MULTICELL THUNDERSTORMS TO DEVELOP. WIND GUSTS OF UP TO 60 KTS ARE POSSIBLE IN PLACES. SOME HAIL IS ALSO POSSIBLE, THAT MAY LOCALLY EXCEED SEVERE LIMITS.

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