CONVECTIVE FORECAST
VALID 06Z FRI 16/05 - 06Z SAT 17/05 2003
ISSUED: 15/05 22:57Z
FORECASTER: GROENEMEIJER

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF FINLAND AND THE RUSSIAN FEDERATION

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN SPAIN

GENERAL THUNDERSTORMS ARE FORECAST ACROSS EASTERN SPAIN, SOUTHERN FRANCE, PARTS OF CENTRAL EUROPE, THE SOUTHERN BALKANS, PARTS OF THE UKRAINE, BELARUS, THE RUSSIAN FEDERATION, FINLAND AND OVER PARTS OF SWEDEN

SYNOPSIS

MEANDERING WEAK TO MODERATE WESTERLY FLOW IS PRESENT OVER MUCH OF WESTERN AND SOUTHERN EUROPE. A SHARP TROUGH OVER POLAND AND THE UKRAINE IS EXPECTED TO MOVE NORTHEASTWARD DURING THE FORECAST PERIOD. INITIALLY SOUTHERLY UPPER FLOW AHEAD OF THE TROUGH WILL BACK TO SOUTHEAST. SURFACE CYCLOGENESIS IS EXPECTED OVER SOUTHERN FINLAND AS THE TROUGH APPROACHES THE AREA.

DISCUSSION

...FINLAND AND PARTS OF THE RUSSIAN FEDERATION...
A WARM FRONT WILL ACCELERATE NORTHWESTWARD OVER THE AREA AS SURFACE CYCLOGENESIS TAKES PLACE OVER SOUTHERN FINLAND AND SOUTHEASTERLY WINDS INCREASE IN THE WARM SECTOR OF THE DEVELOPING LOW. GFS AND MM5 HINT THAT SOME MARGINAL LATENT INSTABILITY IS PRESENT IN THE WARM AIR-MASS. THIS IN COMBINATION WITH QUITE STRONG LOW-LEVEL /AROUND 30 KT 0-1 KM/ AND SUBSTANTIAL DEEP-LAYER /DIRECTIONAL AND SPEED/ SHEAR AND VERY LOW LCL AND LFC HEIGHTS....WILL PROVIDE FAVOURABLE CONDITIONS FOR WEAK TORNADOES FORMING IN ASSOCIATION WITH CONVECTIVE UPDRAFTS ALONG OR NEAR THE FRONTAL BOUNDARY. THERE IS ALSO A CHANCE OF NON-TORNADIC SEVERE WIND GUSTS NEAR THESE VORTICES AS WELL AS A SMALL THREAT OF LARGE HAIL.

...EASTERN SPAIN...
30 HPA MLCAPE WILL RISE TO 1000-1500 J/KG AS THE BOUNDARY LAYER WARMS IN RESPONSE TO SOLAR HEATING DURING THE MORNING AND AFTERNOON. CONVECTION WILL INITIATE DURING EARLY AFTERNOON. AMOUNT OF INSTABILITY IN COMBINATION WITH MODERATE DEEP-LAYER SHEAR WILL BE ADEQUATE FOR MULTICELL CAPABLE OF PRODUCING LARGE HAIL AND POSSIBLY SOME SEVERE WIND GUSTS AS WELL.

...SOUTHERN BALKANS...
30 HPA-MLCAPE WILL INCREASE TO AROUND 500 J/KG OVER THE SOUTHERN BALKANS DURING THE DAY. WEAK TO MODERATE DEEP-LAYER SHEAR WILL RESULT IN MULTICELLS BEING THE MAIN CONVECTIVE MODE. THERE IS A SMALL THREAT OF LARGE HAIL WITH THE THUNDERSTORMS. GFS RUN SUGGESTS A SMALL MCS MAY FORM OVER SOUTHERN BULGARIA/NORTHERN GREECE. IF CONVECTION INDEED BECOMES CLUSTERED AND WIDESPREAD, PRECIPTIATION AMOUNTS MAY BE HIGH IN PLACES AND CAUSE SOME PROBLEMS LOCALLY. THE OVERALL SEVERE THREAT SEEMS TOO LOW TO WARRANT A RISK CATEGORY AT THE MOMENT.

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