CONVECTIVE FORECAST - UPDATE
VALID 17Z WED 30/04 - 06Z THU 01/05 2003
ISSUED: 30/04 15:55Z
FORECASTER: GROENEMEIJER

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF GERMANY AND POLAND

GENERAL THUNDERSTORMS ARE FORECAST ACROSS THE CENTRAL AND SOUTHERN BRITISH ISLES, GERMANY, MUCH OF FRANCE, MUCH OF THE ALPS, POLAND, THE CZECH REPUBLIC, NORTHWESTERN SLOVAKIA AND EXTREME SOUTHERN SCANDINAVIA.

GENERAL THUNDERSTORMS ARE FORECAST ACROSS NORTHERN UKRAINE, SOUTHEASTERN BELARUS AND PARTS OF RUSSIA.

SYNOPSIS

SOUTHWESTERLY JET IS LOCATED OVER CENTRAL EUROPE. A WAVE HAS FORMED IN THE ASSOCIATED FRONTAL ZONE. CYCLOGENESIS IS TAKING PLACE AT THE TOP OF THE WAVE OVER NORTHWESTERN GERMANY MOVING RAPIDLY EASTNORTHEASTWARD. A SLACK UPPER TROUGH IS LOCATED OVER EASTERN EUROPE.

DISCUSSION

...SLGT RISK AREA...
COLD FRONT OVER WESTERN GERMANY WILL ACCALERATE EASTWARD WHILE SURFACE CYCLONE DEEPENS. MARGINAL INSTABILITY HAS FORMED OVER MUCH OF GERMANY AND POLAND AND MIGHT INCREASE SOMEWHAT FURTHER AS UPPER LEVEL COLD ADVECTION TAKES PLACE FROM EASTERN FRANCE INTO GERMANY EASTWARD. INITIATION OF CONVECTION IS ANTICIPATED OVER THE NEXT FEW HOURS. VERY STRONG DEEP-LAYER SHEAR /~ 70 -80 KTS 0-6 KM BULK SHEAR/ AND STRONG LINEAR FORCING WILL AID STORM ORGANISATION INTO LINEAR CONVECTIVE MODES /SQUALL LINES. THERE IS A RISK OF DAMAGING WINDS WITH THIS ACITIVITY. SOME HAIL NEAR SEVERE LIMITS IS ALSO POSSIBLE. GIVEN LOW LCL HEIGHTS, A MINOR THREAT OF TORNADOES IS ALSO PRESENT. GIVEN STRONG DYNAMIC FORCING, ACTIVITY WILL LIKELY RETAIN MUCH OF ITS INTENSITY OVERNIGHT MOVING INTO POLAND AND THE CZECH REPUBLIC.

...NORTHWESTERN FRANCE, SOUTHERN BRITAIN, BENELUX...
NUMEROUS THUNDERSTORMS HAVE FORMED IN THE POSTFRONTAL AIR-MASS OVER THE BRITISH ISLES AND NORTHWESTERN FRANCE. AMOUNT OF SHEAR /~35-40KT 0-6 KM BULK/ MAY BE MARGINALLY SUFFIENT TO SUPPORT SHORT-LIVED ROTATING UPDRAFTS. SMALL DIRECTIONAL SHEAR AND RELATIVELY HIGH LCL HEIGHTS OVER BRITAIN STRONGLY LIMITS CHANCE OF TORNADOES. SOME STORMS MAY PRODUCE SMALL HAIL AND STRONG GUSTS, MOSTLY BELOW SEVERE LIMITS. STORMS WILL SPREAD INTO THE BENELUX COUNTRIES DURING THE NEXT FEW HOURS.

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