VALID 16Z SUN 17/11 - 06Z MON 18/11 2002
ISSUED: 17/11 14:38Z
FORECASTER: GROENEMEIJER

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE BALTIC STATES AND THE SOUTHERN BALTIC SEA

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE MEDITERRENEAN SEA

GENERAL THUNDERSTORMS ARE FORECAST ACROSS THE CHANNEL REAGION AND THE SOUTHERN NORTH SEA, THE SOUTHERN BALTIC SEA, OVER THE EASTERN BAY OF BISCAY, THE ATLANTIC WEST OF THE IBERIAN PENINSULA, THE WESTERN AND PARTS OF THE CENTRAL MEDITERRANEAN AND PARTS OF SOUTHEASTERN FRANCE.

SYNOPSIS

A LONGWAVE TROUGH IS PRESENT ALONG AN AXIS FROM THE BRITISH ISLES TO EASTERN SPAIN. A JET STREAK IS APPROACHING THE CENTRAL MEDITERRANEAN AREA. IN RESPONSE A BAROCLINIC WAVE WILL DEVELOP. ANOTHER SURFACE CYCLONE IS ALREADY PRESENT FURTHER DOWNSTREAM OVER THE SOUTHERN BALTIC SEA. AIR MASS IS GENERALLY QUITE STABLE OVER EUROPEAN MAINLAND. OVER CENTRAL MEDITERRANEAN AIR MASS IS MARGINALLY UNSTABLE.

DISCUSSION

...THE SOUTHERN BALTIC SEA AND PARTS OF THE BALTIC STATES...
A STRONG SURFACE CYCLONE HAVING A STRONG WIND FIELD ON ITS SOUTHERN FLANK IS PRESENT OVER THE SOUTHERN BALTIC SEA AND S EXPECTED TO TRACK EASTNORTHEASTWARD DURING THE FORECAST PERIOD. ALONG A SURFACE TROUGH SOUTH OF THE CYCLONE CENTER SOME LINEAR CONVECTION MAY DEVELOP. GIVEN STRONG WIND FIELD AND STRONG WIND SHEAR, THESE CONVECTIVE STORMS WILL LIKELY BE ACCOMPANIED BY SEVERE WIND GUSTS OF UP TO 65 KNOTS. EVEN IF CONVECTION DOES NOT DEVELOP AREA SHOULD EXPECT SOME MARGINALLY SEVERE WIND GUSTS.

...SOUTH CENTRAL MEDITERRANEAN...
IN RESPONSE TO THE APPROACH OF A JET STREAK SURFACE CYCLOGENESIS OVER THE THYRRENEAN SEA IS EXPECTED THIS AFTERNOON. WAVE WILL DEVELOP IN FRONTAL ZONE NOW PRESENT ALONG A LINE FROM NORTHESASTERN ALGERIA TO THE SOUTH OF SARDINIA TO NORTHEASTERN ITALY. OVERNIGHT...WIDESPREAD CONVECTION IS EXPECTED TO DEVELOP ALONG COLD FRONT SOUTH OF SARDINIA. GIVEN EXPECTED CAPE VALUES OF AROUND 1000 J/KG AHEAD OF THE SYSTEM AND QUITE HIGH S.R.HELICITY VALUES THESE STORMS MAY DEVELOP INTO SUPERCELLS. THE SYSTEM WILL LIKELY EVELOVE INTO A LINEAR CONVECTIVE SYSTEM AS MORNING APPROACHES. THERE IS A CHANCE OF TORNADOES, SEVERE WIND GUSTS AND LARGE HAIL.

...NORTHEASTERN ITALY...
FRONTAL ZONE WILL LIKELY START MOVING NORTHWARD IN REPSONSE TO DEVELOPING SURFACE CYCLONE. WIND SHEAR WILL BE MARGINALLY SUFFICIENT FOR THE DEVELOPMENT OF ROTATING UPDRAFTS, BUT INSTABILITY MIGHT BE TOO LOW FOR STRONG CONVECTION TO DEVELOP. THEREFORE A SLIGHT RISK IS NOT ISSUED AT THIS TIME.

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