VALID 15Z THU 10/10 - 00Z FRI 11/10 2002
ISSUED: THU 10/10 15:32Z
FORECASTER: GROENEMEIJER

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR SOUTHERN ITALY, THE ITALIAN ISLANDS AND THE ASSOCIATED WATERS, THE SOUTHERN ADRIATIC AND THE COASAL AREAS OF THE SOUTHWESTERN BALKANS.

GENERAL THUNDERSTORMS ARE FORECAST OVER SURROUNDING THE SLIGHT RISK AREA

SYNOPSIS

UPPER LOW IS PRESENT OVER THE WESTERN MEDITERRENEAN. A STRONG JET IS PRESENT TO THE SOUTHWEST AND SOUTH OF THE SYSTEM. VARIOUS SHORTWAVES ARE EMBEDDED IN THIS FLOW. OVER THE CENTRAL MEDITTERANEAN AHEAD OF COLD FRONTAL ZONE OVER SOUTHERN ITALY, SICILY AND ADRIATIC STRONG WARM ADVECTION IS TAKING PLACE.

DISCUSSION

...SICILY...THYRRENEAN SEA...MALTA...SARDINIA...CORSICA...
LICT (TRAPANI) SOUNDINGS SHOW 1000-1500 J/KG CAPE AND SLIGHTLY VEERING BOUNDARY-LAYER WINDS UNDER 50 KT MID-LEVEL WINDS, CREATING A FAVOURABLE ENVIRONMENT FOR SUPERCELLS. SOME ISOLATED CONVECTION IS VISIBLE ON SATELLITE IMAGERY WEST AND SOUTHWEST OF SICILY. GIVEN OBSERVED SHEAR PROFILES THESE ISOLATED CELLS ARE LIKELY SUPERCELLULAR. IN THE NEXT FEW HOURS THESE STORMS ARE EXPECTED TO INCREASE IN COVERAGE AND AFFECT SICILY AND THE SOUTHERN THYRRENEAN SEA. SEVERE WIND GUSTS AND LARGE HAIL WILL BE ASSOCIATED WITH THESE STORMS. AS LOW-LEVEL SHEAR IS QUITE LOW THE TORNADO POTENTIAL IS QUITE LOW AS WELL. HOWEVER, SOME INCREASE IN LOW-LEVEL SHEAR IS EXPECTED ON THE APPROACH OF A SHORT-WAVE TROUGH.

THE APPROACH OF A SHORTWAVE TROUGH IS CURRENTLY INDUCING CONVECTIVE DEVELOPMENT WEST OF SARDINIA. ACTIVITY IS EXPECTED TO INTENSIFY AND GROW INTO A MCS. BECAUSE OF STRONG WIND-SHEAR THESE STORMS MAY REACH SEVERE LIMITS ALTHOUGH INSTABILITY IS MARGINAL. SOME HAIL OF SIZE AROUND SEVERE LIMITS IS EXPECTED AND SOME HIGH WIND GUSTS. THESE STORMS WILL AFFECT SARDINIA, PARTS OF CORSICA THE THYRRENEAN SEA AND THE WESTERN ITALIAN MAINLAND. CLOSE TO CENTER OF CIRULATION /OVER SARDINIA AND CORSICA/ SYSTEM WILL LIKELY BE BACKBUILDING AND IN COMBINATION WITH OROGRAPHIC FORCING VERY HIGH PRECIPITATION AMOUNTS CAN BE EXPECTED. THIS MEANS THERE IS A RISK OF FLASH FLOODING.

...EXTREME SOUTHEASTERN ITALY...ADRIATIC...EXTREME WESTERN BALKANS...
COLD FRONT LOCATED EAST OF SICILY, SOUTHERN ITALY AND THE ADRIATIC IS EXPECTED TO PROGRESS EASTWARD. FRONTAL WAVE EAST OF SICILY IS MOVING NORTHEASTWARD ALONG FRONTAL ZONE. WAVE IS ACCOMPANIED BY LARGE MCS. ALONG SOUTHERN PART OF FRONT WHERE INSTABILITY AND LOW-LEVEL SHEAR ARE EXPECTED TO BE HIGHEST SOME SEVERE STORMS ARE EXPECTED. AS SHEAR IS STRONG /ADEQUATE FOR UPDRAFT ROTATION/ AS INDICATED BY THE 12Z BRINDISI SOUNDING (LIBR) SOME DAMAGING GUSTS AND LARGE HAIL ARE EXPECTED. HIGH MOISTURE OF PROFILE WILL TEND TO SLOW DOWN OUTFLOW-FORMATION, SO THAT SOME UPDRAFTS MAY LIVE LONG ENOUGH TO DEVELOP STRONG ROTATION. THIS MEANS THAT IN SPITE OF CLUSTERING OF CONVECTION A CHANCE FOR TORNADOES EXISTS.

...MEDITERRANEAN SOUTH OF BALEARES...

SOME THUNDERSTORMS ARE PRESENT IN THE AREA GIVING RISE TO STRONG VERTICAL MOMENTUM FLUXES. COMBINATION OF THESE STORMS AND STRONG GRADIENT IN THE AREA YIELDS A RISK OF SEVERE GUSTS.

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