CONVECTIVE FORECAST - UPDATE
VALID 11Z WED 21/05 - 06Z THU 22/05 2003
ISSUED: 21/05 11:04Z
FORECASTER: GROENEMEIJER

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN POLAND, PARTS OF BELARUS, EXTREME SOUTHEASTERN ESTONIA, EXTREME WESTERN UKRAINE, PARTS OF THE CENTRAL BALKANS.

GENERAL THUNDERSTORMS ARE FORECAST ACROSS MUCH OF CENTRAL EUROPE, SCOTLAND, THE NORTHEN ADRIATIC, THE BALKANS, PARTS OF SWEDEN AND FINLAND AS WELL AS EASTERN PARTS BALTIC STATES, PARTS OF THE UKRAINE, BELARUS AND THE RUSSIAN FEDERATION.

SYNOPSIS

DOMINANT UPPER FEATURE IS A HIGHLY AMPLIFIED UPPER TROUGH HAVING ITS AXIS FROM SOUTHERN SCANDINVIA TO THE ADRIATIC REGION. AN UPPER LOW IS EXPECTED TO GRADUALLY CUT-OFF FROM THE TROUGH OVER THE ADRIATIC. NEAR AND WEST OF THE TROUGH AN AIR-MASS OF POLAR ORIGIN IS PRESENT IN WHICH QUITE SHOWERY CONDITIONS PREVAIL. SOME THUNDER MAY ACCOMPANY OME THE STORMS ESPECIALLY NEAR SUBTLE UPPER LEVEL DISTURBANCES. EAST OF THE TROUGH SUBTROPICAL AIR IS ADVECTED NORTHWARD.

DISCUSSION

...SLIGHT RISK AREA...
A COLD FRONT IS LOCATED NEAR THE POLISH/BELARUSSIAN BORDER SOUTHWARD OVER WESTERN ROMANIA INTO EASTERN YUGOSLAVIA. A WARM FRONT EXTENDS EASTWARD FROM NORTHEASTERN POLAND INTO NORTHERN BELARUS. SOME STORMS ARE ONGOING ATTM, BUT MORE ACTIVITY IS EXPECTED TO INITIATE DURING THE REMAINDER OF THE AFTERNOON ALONG BOTH THE COLD AND WARM FRONTS. IN THE WARM SECTOR SOLAR HEATING AND ONGOING THETA-E ADVECTION WILL DESTABILISE THE AIRMASS /30HPA MLCAPE RISES TO 500 - 1000 J/KG. 0-6 KM BULK SHEAR WILL BE ON THE ORDER OF 40-50 KNOTS, WHICH...IN COMBINATION WITH A QUITE HELICAL FLOW AHEAD OF THE COLD FRONT...WILL ALLOW SOME STORMS TO BECOME SUPERCELLS. MUCH OF THE STORMS WILL CLUSTER DURING THE LATE AFTERNOON AND INTO THE EVENING INTO A FEW MESOSCLAE CONVECTIVE SYSTEMS. ESPECIALLY OVER THE NORTHERN HALF OF THE RISK AREA, STORMS MAY BE ONGOING OVERNIGHT BEING FEEDED BY THE STRONG THETA-E ADVECTION REGIME. WET-BULB-ZERO HEIGHTS NEAR 8000 FT ARE FAVOURABLE OF LARGE HAIL. OTHER IMPORTANT THREAT WITH THE ACTIVITY WILL BE SEVERE WIND GUSTS. QUITE HIGH LCL HEIGHTS DO NOT ALLOW FOR MORE THAN A SMALL RISK OF TORNADOES.

#