CONVECTIVE FORECAST - UPDATE
VALID 12Z TUE 15/04 - 06Z WED 16/04 2003
ISSUED: 15/04 12:30Z
FORECASTER: DAHL

GENERAL THUNDERSTORMS ARE FORECAST ACROSS SW EUROPE.

SYNOPSIS

HIGH-AMPLITUDE UPPER FLOW PATTERN CONTINUING ACROSS EUROPE ... WITH A STRONG CLOSED UPPER HIGH SETTLED OVER THE NORTH SEA. UPPER TROUGH OVER SW EUROPE WILL CLOSE OFF INTO AN UPPER CUT-OFF LOW OVER THE NEXT HOURS ... AND MOVE SOUTHEASTWARD INTO NORTHERN AFRICA.

DISCUSSION

...W MEDITERRANEAN...
TSTMS HAVE FORMED WITHIN WEAKENING THETA-E PLUME OVER THE WESTERN MEDITERRANEAN SEA. CURRENT INDICATIONS ARE THAT PRIMARY FORCING FOR UPWARD MOTION IS DUE TO LOW-LEVEL WARM-ADVECTION AT THE NOSE OF THE PLUME WHERE BULK OF TSTMS APPEARS TO BE LOCATED. THIS SUGGESTS THAT STORMS ARE LIKELY ELEVATED WHICH WOULD ALSO BE SUPPORTED BY PALMA 00Z RADIOSONDE ASCENT. GIVEN THAT STRONGLY CAPPED BOUNDARY-LAYER PARCELS HAVE NO/LITTLE CAPE ... CHANCE OF SFC-BASED STORMS APPEARS TO BE RATHER LOW. IF STORMS DID MANAGE TO ROOT DOWN INTO THE BOUNDARY LAYER ... POTENTIAL FOR SUPERCELLS WOULD EXIST WHICH COULD WELL PRODUCE A BRIEF TORNADO AND SOME HAIL ... BUT HAVE LITTLE CONFIDENCE IN THIS SCENARIO ATTM.

...IBERIAN PENINSULA...
THE EASTERN HALF OF IBERIA IS COVERED BY A LARGE CLOUD SHIELD ... BUT FARTHER WEST ... SCATTERED SHOWERS AND TSTMS SHOULD DEVELOP OVER THE NEXT FEW HOURS BENEATH THE UPPER LOW. PRIND THAT THERE WILL BE ONE OR MORE FOCI OF TSTM FORMATION ASSOCIATED WITH RATHER SMALL-SCALE ... PARTLY ILL-DEFINED VORT MAXIMA WHICH ARE ROTATING ABOUT THE MAIN UPPER LOW. THOUGH SMALL HAIL AND GUSTY WINDS ARE LIKELY TO ACCOMPANY THE THUNDERSTORMS ... THREAT OF ORGANIZED SEVERE SHOULD BE QUITE LOW.

...IRELAND...
ELEVATED MIXED LAYER OVER THE BRITISH ISLES HAS SPREAD FARTHER WEST THAN ANTICIPATED YESTERDAY ... AND CONCOMMITANT WARM MID-LEVEL TEMPERATURES WILL LIKELY PRECLUDE TSTM DEVELOPMENT IN THE ABSENCE OF STRONG FORCING FOR UPWARD MOTION ... AND THE GEN THUNDER FORECAST HAS BEEN DROPPED.

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