CONVECTIVE FORECAST - UPDATE
VALID 06Z THU 24/04 - 06Z FRI 25/04 2003
ISSUED: 24/04 14:35Z
FORECASTER: GROENEMEIJER

GENERAL THUNDERSTORMS ARE FORECAST ACROSS ITALY, THE BALKANS AND MUCH OF EAST-CENTRAL EUROPE

GENERAL THUNDERSTORMS ARE FORECAST ACROSS PARTS OF FRANCE AND THE PYRENEES

GENERAL THUNDERSTORMS ARE FORECAST ACROSS CENTRAL AND SOUTHERN IRELAND, AND SOUTHERN BRITAIN

SYNOPSIS

SOUTHERN BRANCH OF WESTERLY JET SITUATED OVER NORTHERN AFRICA. UPPER TROUGH OVER EASTERN EUROPE EVADES SOUTHEASTWARD AS AN UPPER RIDGE FORMS OVER WESTERN EUROPE. A SOUTHWESTERLY JET IS EJECTING OUT OF THE EASTERN ATLANTIC HAVING ITS EXIT REGION OVER THE SOUTHERN BRITISH ISLES.

DISCUSSION

...THE BALKANS AND EAST-CENTRAL EUROPE...
ALONG PROPAGATING TROUGH AXIS OF EASTERN EUROPEAN TROUGH INSTABILITY DUE TO DAYTIME HEATING SHOULD ALLOW CONVECTIVE ACTIVITY. MODEL OUTPUT SUGGESTS CAPE IN THE ORDER OF 700 J/KG WITHIN THE DAY OVER EASTERN POLAND/ WESTERN WHITE RUSSIA. WEAK VERTICAL SHEAR DOES NOT ARGUE FOR THUNDERSTORM ORGANISATION. SMALL HAIL IS FORECAST IN ASSOCIATION WITH THE STRONGER CELLS. HOWEVER ... INTERACTION OF SINGLE CELLS COULD LEAD TO SHORT-LIVED MESOCYCLONES AND THE ABILITY OF BIGGER HAIL. SEVERE HAIL IS EXPECTED TO BE TOO LOCALISED TO WARRANT A CATEGORICAL RISK. OVER THE MEDITERRANEAN ... DUE TO DIURNAL HEATING SHOWERS AND THUNDERSTORMS MAY FORM OVER LAND. WEAK VERTICAL SHEAR AND WEAK INSTABILITY DO NOT ARGUE FOR THUNDERSTORM ORGANISATION.

...SOUTHERN IRELAND, SOUTHERN BRITAIN...
SATELLITE IMAGERY SHOWS A FRONTAL ZONE OVER THE SOUTHERN BRITISH ISLES. MOIST AIR-MASS SOUTH OF THE FRONTAL ZONE MAY DESTABILISE ENOUGH TO PRODUCE SOME THUNDERSTORMS. GIVEN LOW-LCL HEIGHTS THERE IS A SMALL CHANCE OF WEAK TORNADOES WITH ANY STORM THAT FORMS. SOME STRONG WIND GUSTS AND SMALL HAIL MAY ALSO OCCUR, BUT THESE WILL LIKELY NOT REACH SEVERE LEVELS.

...BENELUX, NORTHERN FRANCE, WEST-CENTRAL GERMANY...
NORTHWARD PROPAGATING AREA OF TOWERING CUMULUS IS EVIDENT ON VISIBLE SATELLITE IMAGERY WITHIN NORTHWARD MOVING PLUME OF RELATIVELY MOIST AIR. SOME WEAK THUNDERSTORMS MAY FORM WITHIN THIS AIR MASS.

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