VALID 18Z TUE 22/10 - 06Z WED 23/10 2002
ISSUED: 22/10 19:33Z
FORECASTER: GATZEN

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTH-CENTRAL EUROPE

GENERAL THUNDERSTORMS ARE FORECAST ACROSS NW EUROPE, SOUTHERN FRANCE, WESTERN ALPS, NORTHERN ITALY, SOUTHEASTERN EUROPE, EASTERN EUROPE

SYNOPSIS

SHORT WAVE TROUGH BELONGING TO EX-KYLE-LOW-PRESSURE-SYSTEM IS ATTACHED TO OLD COLD LONG-WAVE TROUGH OVER SCANDINAVIA AND STARTS TO ROTATE THROUGH THE MEAN TROUGH. OVER SOUTHERN EUROPE ... STRONG STREAM WILL CONTINUE, AND VORT-MAXIMA WILL EFFECT THE MEDITERRANEAN REGION. AT THE SURFACE ... LOW PRESSURE SYSTEM "EX-KYLE" WILL INTENSIFY AND MOVE NNE-WARD.

DISCUSSION

...NORTH-CENTRAL EUROPE...
MAIN SHORT-WAVE-TROUGH REACHES CENTRAL EUROPE NEGATIVELY TILTED WITHIN THE NIGHT. AT LOWER LEVELS ... STRONG COLD AIR ADVECTION WILL TAKE PLACE BEHIND THE COLD FRONT OF SURFACE LOW "EX-KYLE" OVER GREAT BRITAIN. IN FRONT OF THE COLD FRONT ... CONVERGENCE LINE IS PROGGED TO CROSS NORTHERN CENTRAL EUROPE. LEAST COLD AIR ADVECTION SHOULD BE EXPECTED IN THE RANGE OF DENMARK. TEMPS OUT OFF THIS REGION SHOW SOME CAPE (EMDEN) AND SHOWERS/ THUNDERSTORMS SHOULD EMERGE ALONG CONVERGENCE LINE AND PROBABLY ALONG THE FOLLOWING COLD FRONT. FAVOURABLE SHEAR PROFILES SHOULD EXSIST IN CASE OF LOW-LEVEL SOUTHERLY WINDS IN FRONT OF CONVERGENCE LINE ... WITH 30 TO 40 KNOTS SHEAR IN THE LOWEST KILOMETERS. HOWEVER ... IF STORMS COULD FORM ALONG CONVERGENCE LINE ... ORGANISATION WOULD BE LIKELY ... IN CONJUNCTION WITH SEVERE WIND GUSTS WHICH SHOULD BE THE MAIN SEVERE THREAT ... AND SMALL HAIL.

...SOUTHEASTERN EUROPE...
THUNDERSTORMS HAVE FORMED ALONG COLD FRONT IN CONJUNCTION WITH CVA-MAX AND WAA. STORMS MOVE TO THE EAST INTO YUGOSLAVIA. TOGETHER WITH THE COLD FRONT, CONVECTIVE ACTIVITY SHOULD SPREAD SOUTHWARD AND AFFECT THE WHOLE REGION OF ADRIATIC SEA. FORECASTED SHEAR PROFILES DOESN'T LOOK VERY FAVOURABLE SO SEVERE THREAT SHOULD BE SOMEHOW LIMITED ... HOWEVER ... 500 HPA-WINDS ARE INCREASING WITHIN THE NEXT HOURS AND SOME CONSISTEND UPDRAFTS SHOULD FORM. IF OROGRAPHY WILL ENHANCE SRH SOMEWHERE ... ROTATING UPDRAFTS SHOULD BE POSSIBLE ... WITH THE CHANCE OF HAIL AND STRONG WINDGUSTS ... ALTHOUGH CHANCE FOR SEVERE CONVECTION SHOULD BE QUITE LOW.

...SOUTHERN FRANCE, WESTERN ALPS, NORTHERN ITALY...
SOME STORMS HAVE DEVELOPED OVER SOUTHERN FRANCE BY INFLUENCE OF CVA-MAX TRAVELLING EASTWARD. IN CONJUNCTION WITH BEGINNING COLD AIR ADVECTION THESE THUNDERSTORMS SHOULD WEAKEN AT NIGHT. NEW STORMS SHOULD DEVELOP ALONG THE WEST ALPS BY REASON OF OROGRAPHICAL FORCING LINKED WITH VORTICITY ADVECTION. STRONG TO SEVERE THUNDERSTORMS ARE NOT LIKELY DUE TO NOCTURNAL EMISSION. THUNDERSTORM ACTIVITY SHOULD SPREAD EASTWARD AND EFFECT NORTHERN ITALY WITHIN THE NIGHT.

...EASTERN EUROPE...
SHORT-WAVE-TROUGH SITUATED OVER EASTERN GERMANY MIGRATES EASTWARD REACHING WHITE RUSSIA EARLY WEDNESDAY MORNING. COMBINED COLD FRONT WILL CROSS THE FORECAST AREA WITHIN DAY 1- PERIODE. ALONG THE COLD FRONT ... WARM STABLE AIRMASS SHOULD INHIBIT STRONG CONVECTION, IN CONTRAST RADIOSONDE-DATA INSIDE COLD AIRMASS BEHIND THE FRONT SHOW CAPE-VALUES UP TO 200 J/KG (STUTTGART). A FEW THUNDERSTORMS HAVE DEVELOPED OVER SOUTHERN GERMANY ALONG THE TROUGH AXIS, ALREADY STARTING TO WEAKEN. THIS NIGHT ... ONLY A SLIGHT CHANCE FOR THUNDERSTORMS SHOULD EXSIST. MODERATE LOW-LEVEL SHEAR COULD CAUSE SOME CONSISTEND UPDRAFTS, AND SMALL HAIL AND SOME WIND GUSTS COULD OCCUR. HOWEVER ... CHANCE FOR SEVERE CONVECTION IS TOO LOW TO WARRANT A SLIGHT RISK.

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