DAY 1 CONVECTIVE OUTLOOK
VALID 19Z SUN 02/03 - 06Z MON 03/03 2003
ISSUED: 02/03 19:00Z
FORECASTER: DAHL

GENERAL THUNDERSTORMS ARE FORECAST ACROSS SWITHERLAND ... S GERMANY ... ITALY.

SYNOPSIS

SPLIT-FLOW REGIME PERSISTING OVER EUROPE ... WITH STRONG SOUTHERN UPPER FRONTAL ZONE STRETCHING FROM THE BRITISH ISLES INTO THE SE MEDITERRANEAN SEA. PRIMARY FEATURE IS A RATHER STRONG SHORT-WAVE TROUGH ATTM REACHING THE NORTHERN ADRIATIC SEA. LOW-LEVEL CYCLOGENESIS ALREADY UNDERWAY OVER N ITALY AHEAD OF THE UPPER TROUGH ... ASSOCIATED COLD FRONT WILL RAPIDLY CROSS ITALY DURING THE NIGHT. ANOTHER ... RATHER WEAK SFC LOW IS SITUATED OVER THE BENELUX STATES AND NW GERMANY ... THIS FEATURE IS FCST TO FILL TOWARDS THE END OF THE FCST PERIOD.

DISCUSSION

... SWITHERLAND ... S GERMANY...
IN THE WAKE OF THE COLD FRONT ASSOCIATED WITH THE LOW OVER BENELUX/GERMANY ... WEAK SHOWERS AND ISOLATED TSTMS HAVE DEVELOPED AHEAD OF THE SHORT-WAVE TROUGH. THE STRONGER CELLS SHOULD BE CAPABLE OF PRODUCING STRONG WIND GUSTS ALONG WITH SMALL HAIL. THOUGH RADIATIONAL SFC COOLING SHOULD GENERALLY WEAKEN CONVECTIVE ACTIVITY OVER THE NEXT HOURS ... ISOLATED/BRIEF TSTMS APPEAR LIKELY TO RE-DEVELOP LATER TONIGHT /PRIMARILY BEFORE 00Z/ GIVEN SUSTAINED UVM AND CONCOMITANT MID/UPPER COOLING.

... ITALY...
MODELS COHERENTLY ASSUMING STRONG DCVA-RELATED FORCING FOR UPWARD VERTICAL MOTION ALONG THE COLD FRONT OF THE DEVELOPING MEDITERRANEAN LOW. THE PRE-FRONTAL AIRMASS IS NOT CHARACTERIZED BY PARTICULARLY IMPRESSIVE THERMODYNAMIC PROPERTIES ... BUT RATHER DRY MID/UPPER LEVELS AND ONLY SLIGHTLY STABLE LAPSE RATES SHOULD YIELD WEAK POTENTIAL INSTABILITY ... AND ALLOW THE SOUTHWARD SPREADING UVM TO GENERATE SOME 100 J/KG OF CAPE. IN THE VICINITY OF THE VORT MAX ... SHEAR SHOULD BE SUBSTANTIAL /ON THE ORDER OF 60 TO 70 KNOTS IN THE LOWEST 6 KM/. POTENTIAL PROBLEM IS THE SMALL SIZE OF THE VORT MAX AND OF THE ASSOCIATED WIND REGIME ... AND CONVECTION MAY STAY E OF THE FAVORABLY SHEARED ENVIRONMENT. IF TSTMS INDEED FORM IN THE REGION OF STRONG SHEAR ... POTENTIAL EXISTS FOR BRIEF BOWS/LEWPS PRODUCING STRONG/DAMAGING WIND GUSTS AND SOME HAIL ... WHICH MAY BRIEFLY REACH SEVERE LEVELS. UNCERTAINTY ABOUT THE DEGREE OF THE DEVELOPING INSTABILITY ... AND RATHER LOW CONFIDENCE THAT TSTMS WILL BENEFIT FROM THE UPSTREAM BAND OF STRONG MID/UPPER WINDS ... PRECLUDE A SLGT RISK ATTM BUT AN UPGRADE MAY BE NECESSARY WITH LATER OUTLOOKS.

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