CONVECTIVE FORECAST - UPDATE
VALID 14Z SUN 01/06 - 06Z MON 02/06 2003
ISSUED: 01/06 15:18Z
FORECASTER: GROENEMEIJER

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS FRANCE, EASTERN BRITAIN

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS A PART OF RUSSIA

GENERAL THUNDERSTORMS ARE FORECAST ACROSS MUCH OF WESTERN, SOUTH-CENTRAL AND SOUTHERN EUROPE AS WELL AS PARTS OF THE UKRAINE, BELARUS AND RUSSIA

SYNOPSIS

UPPER RIDGE OVER WESTERN EUROPE IS SLOWLY SHIFTING EASTWARD, AS WELL AS ATLANTIC LONGWAVE UPPER TROUGH. LATTER FEATURE WILL BECOME INCREASINGLY NW-SE ORIENTED AND REACH THE SOUTHWESTERN BRITISH ISLES AND WESTERN-FRANCE LATER ON SUNDAY. FURTHER EAST...ACTIVE SHORTWAVE OVER NORTHWEST-RUSSIA CONTINUES EAST. A COLD FRONT IS ANALYZED AT 13Z FROM THE HEBRIDES TO NORTHERN IRELAND TO WESTERN PORTUGAL. A NORTHEASTWARD MOVING (BAROCLINIC) CONVERGENCE LINE FROM CENTRAL ENGLAND TO WESTERN FRANCE WILL REACH SOUTHWESTERN BENELUX MONDAY NIGHT.

DISCUSSION

...FRANCE, BRITAIN......
(MODIFIED) SOUNDINGS AT 12 Z INDICATE THAT SUBSTANTIAL INSTABILITY IS PRESENT AHEAD OF THE CONVERGENCE LINE WHICH IS ANALYZED FROM NEAR EDINBURGH TO LONDON TO LE HAVRE TO LYON AT 13Z. .... AROUND 500 - 1500 J/KG OVER BRITAIN AND AROUND 1500 - 2500 J/KG 50HPA MLCAPE OVER FRANCE. THUNDERSTORMS ARE RAPIDLY FORMING NEAR THE CONVERGENCE LINE OVER PARTS OF WESTERN AND CENTRAL FRANCE. MORE SCATTERED STORMS ARE PRESENT OVER EASTERN FRANCE. WIND SHEAR WILL BE SMALL OVER CENTRAL AND EASTERN FRANCE. HIGH INSTABILITY AND DRY MID-LEVELS GIVE A POTENTIAL FOR LARGE HAIL ANDSTRONG DOWNBURSTS. THE ACTIVITY OVER WESTERN FRANCE IS EXPECTED TO CLUSTER INTO AN MCS. SINCE THERE IS ABOUT 15-20 KT 0-1 KM LOW-LEVEL SHEAR PRESENT OVER ENGLAND, AND DEEP-LAYER SHEAR WILL INCREASE DURING THE NEXT HOURS, THE MCS MAY PRODUCE SEVERE WIND GUSTS. ALSO, THERE IS A CHANC OF LARGE HAIL WITH THE STORMS. SINCE LOW-LEVEL WINDS ARE STRONGLY VEERING WITH HEIGHT AHEAD OF THE CONVERGENCE LINE YIELDING A QUITE HELICAL INFLOW LAYER TO THE CONVECTIVE SYSTEM, THERE IS A CHANCE THAT ONE OR TWO TORNADOES WILL OCCUR OVER EASTERN BRITAIN, WHERE LCL'S ARE QUITE LOW.

...CENTRAL EUROPE, ITALY, SPAIN...
DAYTIME-HEATING HAS RESULTED IN 50-HPA MLCAPES CLIMBING TO 500-1500 J/KG. THE MAJORITY OF THE STORMS WILL LIKELY BE SHORT-LIVED, DUE TO REALIVELY WEAK SHEAR. LOCALLY, MARGINAL LARGE HAIL IS POSSIBLE WITH THE STRONGER STORMS, BUT A SLIGHT RISK IS NOT NECESSARY.

...RUSSIA...
STRONG UVM IS EXPECTED OVER PARTS OF NORTHWEST-RUSSIA DUE TO STRONG DCVA AND WAA AHEAD OF SOUTHEASTWARD MOVING COLDFRONT. ALTHOUGH INSTABILITY WILL BE MARGINAL, DEEP-LAYER SHEAR IS ADEQUATE TO SUPPORT ORGANIZED STORMS. THE 12Z NIZHNY NOVGOROD (27459) SOUNDING SHOWS HIGHLY HELICAL LOW-LEVEL FLOW SUPPORTIVE OF ROTATING UPDRAFTS/SUPERCELLS. SOME LOCALIZED DAMAGING WIND GUSTS AND LARGE HAIL ARE POSSIBLE WITH THESE STORMS.

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