VALID 06Z TUE 26/11 - 06Z WED 27/11 2002
ISSUED: 25/11 18:57Z
FORECASTER: GROENEMEIJER

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHERN ITALY AND ADJACENT PARTS OF THE MEDITERRANEAN

GENERAL THUNDERSTORMS ARE FORECAST ACROSS PARTS OF THE MEDITERRANEAN AREA

SYNOPSIS

AN UPPER LOW IS EXPECTED TO CUT-OFF FROM AN ELONGATED TROUGH CURRENTLY ALONG A LINE FROM THE BRITISH ISLES TO EASTERN SPAIN. A JET STREAK ALONG ITS SOUTHERN FLANK WILL ROTATE INTO THE MEDITERREANEAN NEAR SOUTHERN ITALY. STRONG ASSOCIATED UPW3ARD MOTION DUE TO DCVA WILL LEED TO SOME FURTHER DEEPENING OF A SURFACE LOW NOW PRESENT JUST NORTH OF ALGERIA THAT IS EXPECTED TO MOVE A BIT NORTHEASTWARD.

DISCUSSION

...SOUTHERN ITALY AND ADJACENT PARTS OF THE MEDITERRANEAN...
THE ATMOSPHERE OVER THE AREA IS GENERALLY MARGINALLY UNSTABLE WITH MLCAPE VALUES BETWEEN 0 AND 500 J/KG. THERE ARE QUESTIONS CONCERNING THE DEPTH OF THE MOIST BOUNDARY LAYER BY TOMORROW MORNING. THE LICT /TRAPANI/ SOUNDING SHOWS A BOUNDARY LAYER OF ONLY 30 HPA THAT MAY BE THE RESULT OF LOCAL OROGRAPHIC EFFECTS WHILE LIBR /BRINDISI/ HAS A MOIST BOUNDARY LAYER OF 80 HPA. IF INDEED A MOIST BOUNDARY LAYER OF 80 HPA IS PRESENT TOMORROW MORNING, MLCAPE VALUES CAN BE AROUND OR EVEN SLIGHTLY ABOVE 1000 J/KG. NORTH OF SICILY INSTABILITY WILL LIKELY BE MORE MODEST. STRONG UPWARD VERTICAL MOTION ASSOCIATED ON APPROACH AFOREMENTIONED JET STREAK WILL FACILITATE THE INITIATION OF CONVECTION AS SOON AS THE CAP HAS WEAKENED ENOUGH THAT MOIST BOUNDARY LAYER CAN REACH ITS LFC. QUITE STRONG SHEAR PROFILES ARE EXPECTED TOMORROW, THAT ARE IN PRINCIPLE ADEQUATE FOR THE FORMATION OF ROTATING UPDRAFTS/SUPERCELLS. HOWEVER, GIVEN STRONG LINEAR FORCING AND DRY MID-LEVELS FORMATION OF A LINEAR MCS WITH STRONG WIND GUSTS SEEMS MOST LIKELY. SOME MARGINALLY SEVERE HAIL IS ALSO POSSIBLE.

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