CONVECTIVE FORECAST - UPDATE
VALID 14Z SAT 24/05 - 06Z SUN 25/05 2003
ISSUED: 24/05 14:48Z
FORECASTER: GROENEMEIJER

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHWESTERN AND NORTHERN GERMANY, SOUTHERN DENMARK AND SOUTHERN SWEDEN

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL BALKANS

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UKRAINE, SOUTHERN BELARUS AND A PART OF SOUTHWESTERN RUSSIA

GENERAL THUNDERSTORMS ARE FORECAST ACROSS ENGLAND, WALES AND SCOTLAND, MUCH OF GERMANY, SWITZERLAND AND EASTERN FRANCE, SOUTHERN DENMARK, SOUTHERN SWEDEN, MUCH OF THE BALKANS, THE UKRAINE, SOUTHERN BELARUS A PART OF RUSSIA AND TURKEY.

SYNOPSIS

A TROUGH IS AMPLYFYING OVER WESTERN FRANCE. A SOUTHSOUTHWESTERLY JET STREAM PRESENT ON ITS EASTERN FLANK IS ASSOCIATED WITH A FRONTAL ZONE FROM SOUTHERN SCANDINAVIA TO WESTERN IBERIA. A MODERATE WESTERLY FLOW IS PRESENT OVER NORTHEASTERN EUROPE. A BROAD COLD UPPER LOW IS LOCATED OVER THE AEGEAN SEA REGION.

DISCUSSION

...GERMANY, DENMARK AND SWEDEN...
AN ALMOST STATIONARY FRONT IS LOCATED FROM CENTRAL SWEDEN OVER NORTHERN DENMARK, NORTHWESTERN GERMANY TO CENTRAL FRANCE. STRONG WARM ADVECTION IS TAKING PLACE EAST OF THE FRONTAL ZONE WHERE AN ELEVATED MIXED LAYER CAN BE OBSERVED. OBSERVED UPPER-AIR SOUNDINGS SHOW A QUITE STRONG CAP TO BE IN PLACE OVER MUCH OF GERMANY. AS BOUNDARY LAYER DEW POINTS HAVE RISEN TO AROUND 16 C OVER NORTHWESTERN AND NORTHERN GERMANY, SOME STORMS ARE EXPECTED TO INITITIATE NEAR THE FRONTAL ZONE /WHERE THE CAP IS THE WEAKEST/ DURING THE REMAINDER OF THE AFTERNOON AND EVENING. QUITE STRONG DEEP-LAYER SHEAR WILL BE ADEQUATE FOR THE DEVELOPMENT OF A FEW SUPERCELLS WITH A RISK OF LARGE HAIL, SEVERE WIND GUSTS AND ...GIVEN STRONG LOW LEVEL DIRECTIONAL SHEAR... A SMALL THREAT OF TORNADOES. THE ACTIVITY IS EXPECTED TO AFFECT/DEVELOP OVER DENMARK AND SWEDEN LATER IN THE EVENING AND OVERNIGHT.

...BALKANS...
QUITE HIGH /AROUND 1000 J/KG 30 HPA/ MLCAPE OVER PART SOF THE CENTRAL BALKANS IN COMBINATION WITH MODERATE SHEAR VALUES WILL BE ADEQUATE FOR THE DEVELOPMENT OF A FEW MULTICELL CLUSTERS, THAT ARE CAPABLE OF PRODUCING LARGE HAIL AND SOME STRONG /POSSIBLY MARGINALLY SEVERE/ WIND GUSTS.

...UKRAINE, BELARUS AND RUSSIA...
HIGH /2000 J/KG/ 30 HPA-MLCAPE AND LITTLE CAP OVER THE REGION AND DRY MID-LEVELS IS ADEQUATE FOR THE FORMATION OF SOME STRONG SINGLE- OR MULTICELLS. GIVEN THAT MID-LEVELS ARE QUITE DRY, EVAPORATIONAL COOLING MAY CAUSE STRONG DOWNDRAFTS TO FORM, LEADING TO SEVERE GUSTS. ALSO, SOME LARGE HAIL IS LIKELY WITH SOME OF THE STORMS.

...SOUTHERN AND CENTRAL GERMANY, EASTERN FRANCE, SWITZERLAND ....
STRONG CAP SEEMS TO BE INHIBITING CONVECTIVE DEVELOPMENT OVER THE AREA. IN THE SECOND HALF OF THE EVENING AND OVERNIGHT SOME LIGHT CVA IS INDICATED BY MM5 AND GFS, WHICH MAY HELP TO INTIATE CONVECTION. IF CONVECTION DOES DEVELOP, IT HAS THE POTENTIAL TO PRODUCE SOME STRONG WIND GUSTS, THAT MAY POSSIBLY BE MARGINALLY SEVERE IN PLACES BECAUSE MID AND LOWER TROPOSPHERE ARE RELATIVELY DRY AND SUSTAIN STRONG EVAPORATIONAL COOLING. GIVEN UNCERTAINTY ABOUT EXTENT OF THE INITIATION OF THE CONVECTION AND THE LIMITED RISK INVOLVED IF CONVECTION DOES FORM, WE RAFRAIN FROM ISSUING A CATEGORICAL RISK FOR THE AREA AT THIS MOMENT.

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