CONVECTIVE FORECAST
VALID 06Z THU 10/04 - 06Z FRI 11/04 2003
ISSUED: 09/04 18:45Z
FORECASTER: GATZEN

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHERN AND CENTRAL MEDITERRANEAN, GREECE

GENERAL THUNDERSTORMS ARE FORECAST ACROSS NORTHERN CENTRAL MEDITERRANEAN, ITALY, BALKANS

SYNOPSIS

STEERING LONG-WAVE TROUGH PLACED OVER CENTRAL EUROPE. STRONG WESTERLY CURRENT EXTENDING OVER SOUTHERN MEDITERRANEAN AND NORTHERN AFRICA. SHORT-WAVE TROUGH SITUATED OVER NORTHWESTERN AFRICA MIGRATES ENE-WARD. STRONG JETSTREAK AT IT'S SOUTHEASTERN FLANK WILL SPREAD INTO SOUTHERN MEDITERRANEAN.

DISCUSSION

...SOUTHERN AND CENTRAL MEDITERRANEAN, GREECE...
WARM AIRMASS ORIGINATED FROM NORTHERN AFRICA WILL DISPERSE INTO SOUTHERN CENTRAL MEDITERRANEAN EAST OF MENTIONED SHORT-WAVE TROUGH. ABOVE THE BOUNDARY-LAYER ... DUE TO DIABATIC HEATING OVER THE ATLAS MOUNTAINS STEEP LAPSE RATES ARE EXPECTED. AS WATER SURFACE TEMPERATURE IS STILL RELATIVELY LOW, INSTABILITY SHOULD BE LIMITED SOMEHOW. ONCE STRONG JETSTREAK APPROACH SOUTHERN MEDITERRANEAN, SYNOPTIC SCALE LIFT IS FORECAST. EVEN THOUGH WARM AIRMASS SHOULD BE RELATIVELY DRY, CONVECTION SHOULD BE POSSIBLE ... AND ELEVATED THUNDERSTORMS SHOULD FORM... AND PROBABLY ROOT TO THE BOUNDARY LAYER. SUPERCELLS MAY FORM DUE TO MODERATE VERTICAL SHEAR AT LOWER LEVELS. SEVERE WIND GUSTS AND LARGE HAIL COULD BE POSSIBEL WITHIN THE STRONGEST CONVECTION. HOWEVER ... LATEST MODEL OUTPUT SUGGEST THE DEVELOPMENT OF A CONVERGENCE LINE BENEATH THE SHORT-WAVE TROUGH, AND PROBABLY AN ORGANISED LINE OF THUNDERSTORMS WILL SPREAD EASTWARD, EFFECTING GREECE ON LATE THURSDAY/ EARLY FRIDAY. STRONG TO SEVERE WINDGUSTS AND LARGE HAIL MAY OCCUR.

...NORTHERN CENTRAL MEDITERRANEAN, ITALY, BALKANS...
ANOTHER SHORT-WAVE TROUGH ROTATES ALONG THE EUROPEAN LONG-WAVE TROUGH, REACHING ITALY AND THE BALKANS ON THURSDAY. WARM AIR ADVECTION AND CVA SHOULD LEAD TO STRONG SYNOPTIC SCALE LIFT. SOME ELEVATED THUNDERSTORMS MAY FORM DURING THE DAY AND PROBABLY ROOT TO THE BOUNDARY LAYER. AS VERTICAL SHEAR SHOULD BE RELATIVELY HIGH, DEVELOPING THUNDERSTORMS COULD LIKELY ORGANISE. HOWEVER ... THUNDERSTORM POTENTIAL IS TOO LOW TO WARRANT A SLIGHT RISK THOUGH. HEAVY RAINFALL IS EXPECTED ANYWAY.

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