CONVECTIVE FORECAST
VALID 06Z TUE 20/05 - 06Z WED 21/05 2003
ISSUED: 19/05 19:28Z
FORECASTER: HUGO

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS CENTRAL/NORTHERN ITALY, SOUTHERN AUSTRIA, SLOVENIA, CROATIA & BOSNIA HERCEGOVINA

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS CENTRAL/EASTERN POLAND, CENTRAL/SOUTHWEST BELARUS & PARTS OF SLOVAKIA, HUNGARY & ROMANIA

GENERAL THUNDERSTORMS ARE FORECAST ACROSS THE MAJORITY OF EUROPE EXCEPT; IRELAND, SOUTHWEST MED & CENTRAL/EASTERN UKRAINE & WESTERN RUSSIA

SYNOPSIS

A FILLING LONG WAVE CLOSED MID LEVEL TROUGH OVER THE NORTHERN BRITISH ISLES WILL MOVE NE=WARDS INTO SCANDINAVIA...IN ITS WAKE A 500MB RIDGE FEATURE IN ASSOCIATION WITH AN E=WARD SURFACE EXTENSION OF THE AZORES HIGH WILL MOVE INTO W=ERN PARTS OF EUROPE...CENTRAL & N=ERN PARTS OF EUROPE WILL BE DOMINATED BY LOW PRESSURE & ASSOCIATED FRONTAL FEATURES...WHILE FAR E=ERN REGIONS OF EUROPE CONTINUE TO BE DOMINATED BY A WEAK SURFACE HIGH PRESSURE

DISCUSSION

...CENTRAL/NORTHERN ITALY & SURROUNDING AREAS...
A WEAK SURFACE AREA OF LOW PRESSURE WILL BE SITUATED OVER N=ERN PARTS OF ITALY DURING TUESDAY WITH A SLOW PROGRESS E=WARDS DURING THE DAY...FORECAST SOUNDINGS IN ASSOCIATION WITH THIS FEATURE INDICATE AN UNSTABLE ATMOSPHERE WITH MLCAPE VALUES OF BETWEEN 600 & 700J/KG WITH SBCAPE VALUES POSSIBLY EXCEEDING 1000J/KG...SOLAR INDUCED TSTSM ARE EXPECTED TO DEVELOP WITHIN THE SLGT RISK REGION BY LATE MORNING AND INTO THE EARLY AFTERNOON...THERE IS LITTLE OR NO SHEAR PRESENT (0-3KM S-RH 40 TO 60M2/S2) SO NO MAJOR CONVECTIVE ORGANISATION IS EXPECTED APART FROM POSSIBLY IN ASSOCIATION WITH THE LOW PRESSURE'S E=WARD MOVING COLD FRONT FEATURE...WITH THE HIGH CAPE VALUES, WBZ HEIGHTS BETWEEN 6000FT AND 7000FT & LOW LFC/LCL'S LEVELS SOME INTENSE RAINFALL, MEDIUM TO LARGE HAIL & AND GUSTY SURFACE WINDS (40-50MPH) ARE ALL POSSIBLE. CONVECTIVE DEVELOPMENT WILL GRADUAL DECAY DURING THE EVENING HOWEVER SOME NOCTURNAL CLOUD TOP COOLING IS POSSIBLE TO CREATE SOME MINIMUL LONGER TERM TSTSM.

...CENTRAL/EASTERN POLAND, CENTRAL/SW BELARUS & PARTS OF SLOVAKIA, HUNGARY & ROMANIA...
THERE IS A SLGT RISK OF SEVERE TSTSM IN THE ABOVE REGIONS IN ASSOCIATION WITH A THERMAL PLUME AHEAD OF AN ADVANCING E=WARD MOVING LOW PRESSURE & ITS ASSOCIATED COLD FRONTAL FEATURE...CONVECTIVE DEVELOPMENT WILL OCCUR ON OR JUST AHEAD OF THE E=WARD MOVING COLD FRONT DURING THE LATTER PART OF THE MORNING AND INTO THE AFTERNOON...MLCAPE VALUES OF BETWEEN 100 AND 200J/KG ARE EXPECTED BUT WITH POSSIBLE SBCAPE VALUES EXCEEDING 1000J/KG INTO THE AFTERNOON...PVA IN ASSOCIATION WITH THE E=WARD MOVING COLD FRONT WILL AID UPLIFT...WITH SOME MODERATE 0-3KM SHEAR (170-180M2/S2) & A VGP VALUE OF BETWEEN 0.2 AND 0.3 THERE IS SCOPE FOR SOME ORGANISED TSTSM DEVELOPMENT ON OR JUST AHEAD OF THE COLD FRONT WITH A MINIMAL RISK OF SUPERCELL DEVELOPMENT...WITH FORECAST WBZ HEIGHTS OF BETWEEN 8000FT AND 9000FT AND THE MODERATE SHEAR LEVELS SOME MEDIUM TO LARGE SIZED HAIL IS POSSIBLE AND AN ISOLATED TORNADO CANNOT BE RULED OUT ESPECIALLY SEEING LFC AND LCL'S ARE EXECTED TO BE BETWEEN 3000 AND 5000FT...A REDUCING SOLAR INPUT LATER IN THE DAY WILL REDUCE THE CONVECTIVE ACTIVITY SOMEWHAT BUT ANY ORGANISED TSTSM DEVELOPMENT ON OR AHEAD OF THE COLD FRONT FEATURE WITHIN THE THERMAL PLUME WILL LAST WELL INTO THE EVENING PERIOD BEFORE SLOWLY DECAYING OVERNIGHT.

...REST OF EUROPE, EXCEPT; SW MED, WESTERN FRANCE, IRELAND & WESTERN RUSSIA...
WITH LOW PRESSURE IN CHARGE ACROSS A LARGE PART OF EUROPE, ESPECIALLY OVER MORE N=ERN PARTS OF EUROPE THERE IS A REASONABLE EXPECTANCY FOR ISOL TO SCT TSTSM DEVELOPMENT WITHIN THE GEN RISK AREA(S)...THERE ARE EXCEPTIONS TO THIS WITH W=ERN BRITAIN & FRANCE HAVING A TEMPORARY RISK OF CONVECTIVE DEVELOPMENT DURING THE FIRST HALF OF TUESDAY BUT AS AN INCREASING AMOUNT OF SUBSIDENCE OCCURS IN ASSOCIATION WITH THE E=WARD MOVING MID-LEVEL RIDGE AND SURFACE HIGH PRESSURE CONVECTIVE ACTIVITY WILL REDUCE IN FREQUENCY INTO THE AFTERNOON AND EVENING...THIS PROCESS WILL CONTINUE TO HEAD E=WARDS INTO SOME PARTS OF W=ERN GERMANY...FORECAST SOUNDINGS ACROSS A LARGE PART OF SCANDINAVIA & SE=ERN REGIONS OF EUROPE (GREECE, TURKEY) SHOW POSSIBLE AIRMASS/SOLAR RELIANT CONVECTIVE DEVELOPMENT DURING TUESDAY AFTERNOON ESPECIALLY...THERE IS LITTLE OR NO SHEAR PRESENT OVER SCANDINAVIA SO ANY CONVECTIVE ACTIVITY WILL BE BELOW SEVERE LEVELS HOWEVER SOME HEAVY RAIN AND MINIMAL GUSTY SURFACE WINDS ARE POSSIBLE BUT ANY CONVECTION WILL SLOWLY DECAY TOWARDS SUNSET...THIS PROCESS IS ALSO EXPECTED ACROSS PARTS OF GREECE AND INTO TURKEY, HOWEVER WITH HIGHER SURFACE TEMPERATURES HERE DURING THE AFTERNOON CONVECTIVE DEVELOPMENT MAYBE SOMEWHAT MORE POTENT BUT AGAIN GENERALLY REMAINING BELOW SEVERE LIMITS AND DECAYING TOWARDS SUNSET.

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