DAY 1 CONVECTIVE OUTLOOK
VALID 12Z FRI 31/01 - 00Z SAT 01/02 2003
ISSUED: 31/01 12:22Z
FORECASTER: GATZEN

THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS WESTERN MEDITERRANEAN

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE SURROUNDING AREA OF MDT RISK AREA

GENERAL THUNDERSTORMS ARE FORECAST ACROSS MOST PARTS OF THE MEDITERRANEAN

SYNOPSIS

DOWNSTREAM OF HIGH GEOPOTENTIAL OVER THE NORTHERN ATLANTIC, INTENSE UPPER LONG-WAVE TROUGH AMPLIFIES OVER WESTERN EUROPE ... WHEREAS INTENSE SHORT-WAVE TROUGH AFFECTS THE WESTERN MEDITERRANEAN WHILE ROTATING ALONG THE TROUGHS PERIPHIRIE. STRONG COLD AIR ADVECTION HAS REACHED PARTS OF NORTHERN AFRICA. VERY STRONG UPPER JET STREAK (WINDS UP TO 150 KNOTS OVER NORTHERN IBERIAN PENINSULA THIS MORNING) CAUSES CYCLONAL VORTICITY ADVECTION IN THE RANGE OF ITS LEFT EXIT OVER PARTS OF WESTERN MEDITERRANEAN. CYCLOGENESIS HAS ALREADY BEGUN AND STRENGTHENING SURFACE LOW IS SITUATED EAST OF THE BALEARIC ISLANDS. WARM AIR ADVECTION AFFECTS WIDESPREAD AREAS NORTH AND EAST OF THE SURFACE LOW, EXPANDING SOUTHWARDS AT ITS BACK.

DISCUSSION

...WESTERN MEDITERRANEAN...
BEHIND SOUTHWARD REMOVING COLD FRONT STRONG UNIDIRECTIONAL SHEAR AFFECTS THE WESTERN MEDITERRANEAN. SHOWERS AND THUNDERSTORMS HAVE FORMED WITHIN THE COLD AIRMASS WITH A MODERATE CHANCE OF STRONG WIND GUSTS UP TO 50 KNOTS. STRENGHENING WARM AIR ADVECTION ABOVE 800 HPA IS CAUSING WIND SHIFT TO EASTERLY DIRECTIONS. IF STORMS COULD ROUT INTO THE BOUNDARY-LAYER ... STRONG DIRECTIONAL SHEAR COULD RESULT IN HIGH VALUES OF STORM RELATIVE HELICITY. TEMP OF AJACCIO OF 00Z SHOWS STEEP LAPSE RATES WITHIN THE WARM AIRMASS AND DRY AIR ABOVE 750 HPA POINTING TO THE POSSIBILITY THAT SOME OF THE STORMS ROUTE DOWN TO THE BOUNDARY LAYER DUE TO NEGATIVE BUOYANCY AND STRONG DOWNDRAFTS. IF THESE STORMS DEVELOP, LARGE VALUES OF SRH COULD LEAD TO PERSISTENT ROTATING UPDRAFTS WITH A CHANCE OF HAIL, STRONG WIND GUSTS UP TO 70 KNOTS AND POSSIBLY TORNADOS. SEVERE THREAT SHOULD BE GREATEST IN THE AFTERNOON.

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